Rebalanced cell system for redox flow battery

Abstract

Systems and methods for rebalancing cells in a redox flow battery are provided. In one example, a rebalancing battery cell system includes a first rebalancing battery cell in series fluid communication with a second rebalancing battery cell and a hydrogen gas source, the first rebalancing battery cell including a first electrode assembly stack, the first electrode assembly stack has a hydrogen flow path extending therethrough and has a pressure higher than that of an electrolyte in the first electrode assembly stack. Further, the second rebalancing battery cell includes a second electrode assembly stack having a hydrogen flow path extending therethrough and having a pressure higher than that of the electrolyte in the second electrode assembly stack.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Utility Application No. 17 / 821,400, filed on August 22, 2022, entitled “REBALANCING CELL SYSTEM FOR REDOX FLOW BATTERY” The entire contents of the above-identified applications are hereby incorporated by reference for all purposes. Technical Field

[0003] The present description generally relates to systems for rebalancing cells in a redox flow battery and methods for operating such rebalancing cell systems. Background Art

[0004] Redox flow batteries are also suitable for grid-scale storage applications due to their ability to independently scale power and capacity and to charge and discharge with lower performance loss over thousands of cycles compared to conventional battery technologies. All-iron hybrid redox flow batteries are particularly attractive due to the incorporation of low-cost, earth-abundant materials. Typically, iron redox flow batteries (IFBs) rely on iron, salt, and water as electrolytes, thus including simple, earth-abundant and inexpensive materials, and eliminating the incorporation of harsh chemicals and reducing their environmental footprint.

[0005] The IFB may include a positive (redox) electrode where a redox reaction occurs and a positive (redox) electrode where the divalent iron (Fe) in the electrolyte may be reduced and electroplated. 2+ ) of the negative (plating) electrode. The IFB may further include rebalancing the cells to maintain electrolyte health and cell capacity. In previous IFBs, hydrogen flow through the cells to rebalance the cells was performed in a parallel arrangement.

[0006] The inventors have recognized several disadvantages of directing hydrogen flow through the rebalance cells in parallel. For example, the parallel flow arrangement may reduce the flow rate through the rebalance cells and increase the likelihood of hydrogen maldistribution due to uneven pressure drops in each rebalance cell coupled in parallel. Further, multiple devices may be used to drive hydrogen flow in previous IFBs, thereby increasing the production cost and maintenance requirements of the system. Summary of the invention

[0007] In one example, a rebalanced cell system for a redox flow battery can solve the problems described above. In one example, the rebalanced cell system includes a first rebalanced cell, which is fluidly connected in series with a second rebalanced cell and a hydrogen source. In such an example, the first rebalanced cell includes a first electrode stack, the first electrode stack having a hydrogen flow path extending therethrough, and the pressure is higher than the pressure of the electrolyte in the first electrode stack. The second rebalanced cell correspondingly includes a second electrode stack, the second electrode stack having a hydrogen flow path extending therethrough, and the pressure is higher than the pressure of the electrolyte in the second electrode stack. In order to drive the hydrogen flow in the system, the hydrogen source may include a hydrogen tank, which is fluidly connected in series with a hydrogen flow generator (e.g., a venturi injector or a hydrogen injector). For example, the outlet of the hydrogen flow generator may be fluidly connected to the hydrogen inlet in the first rebalanced cell. Alternatively, the hydrogen flow generator may be positioned upstream of the hydrogen tank and include an inlet, which is fluidly connected to the hydrogen outlet port in the second rebalanced cell. Compared to cells arranged in parallel flow, connecting rebalanced cells in series can increase the hydrogen flow rate through each cell and distribute the hydrogen more evenly. Further, connecting rebalanced cells in series enables the system to use a smaller number of flow generators (e.g., a single flow generator) than a parallel rebalanced cell flow arrangement. Thus, rebalanced cell manufacturing and maintenance can be simplified.

[0008] In one example, the first rebalanced cell includes a first hydrogen inlet port, which is in fluid communication with the hydrogen source. The first rebalanced cell further includes a first hydrogen outlet port and / or a first hydrogen release port. Similarly, in such examples, the second rebalanced cell includes a second hydrogen inlet port, which is in fluid communication with one of the first hydrogen outlet port and the first hydrogen release port. The second rebalanced cell further includes a second hydrogen outlet port and / or a second hydrogen release port, which is in fluid communication with the hydrogen source. In this way, hydrogen can flow out from one or both of the outlet port and the release port. Therefore, the hydrogen flow path can be adjusted based on the desired reaction rate in the rebalanced cell, thereby enhancing the rebalanced cell operation.

[0009] It should be understood that the above summary is provided to introduce in a simplified form a series of concepts that are further described in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is uniquely defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to embodiments that solve any disadvantages mentioned above or in any part of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A schematic diagram of an example redox flow battery system is shown that includes a battery cell having redox and electroplating electrodes fluidly coupled to respective rebalance reactors.

[0011] Figure 2A and 2B A perspective view of a rebalanced battery cell including a stack of internally shorted electrode assemblies is shown.

[0012] Figure 3 Shown for Figure 2A and 2B Exploded view of the electrode assembly of a rebalanced battery cell.

[0013] Figure 4A and 4B They are shown respectively Figure 2A and 2B Cross-sectional view and magnified inset of the first H2 flow pattern in the rebalanced battery cell.

[0014] Figure 5A and 5B They are shown respectively Figure 2A and 2B Cross-sectional view and magnified inset of the second H2 flow pattern in the rebalanced battery cell.

[0015] Figure 6-9 An example of a rebalanced battery cell system is shown, where the batteries are arranged in different series flows.

[0016] Fig.10 A flow chart is shown of a method for operating a rebalanced battery cell system including a plurality of series connected battery cells. DETAILED DESCRIPTION

[0017] The following description relates to systems and methods for distributing hydrogen through rebalancing cells in a series flow arrangement. Rebalancing cells maintain the electrolyte health and capacity of a redox flow battery. To perform this function, rebalancing cells requires sufficient hydrogen to flow into the cells in order to support the desired reaction rate. Using a series flow arrangement increases the hydrogen flow rate through the cells and achieves a more balanced hydrogen distribution compared to a parallel flow arrangement.

[0018] Figure 1 A redox flow battery is schematically depicted, comprising an integrated multi-chamber tank having separate positive and negative electrolyte chambers. In some examples, the redox flow battery can be an all-iron flow battery (IFB) utilizing iron redox chemistry at both the positive (redox) electrode and the negative (electroplating) electrode of the IFB. The electrolyte chamber can be coupled to one or more battery cells, each of which includes a positive electrode and a negative electrode. Thus, the electrolyte can be pumped through the positive electrode compartment and the negative electrode compartment that house the positive and negative electrodes, respectively.

[0019] In some examples, the redox flow battery may be a hybrid redox flow battery. A hybrid redox flow battery is a redox flow battery that may be characterized by depositing one or more electroactive materials as a solid layer on an electrode (e.g., a negative electrode). A hybrid redox flow battery may, for example, include chemical species that may be electroplated as a solid on a substrate via an electrochemical reaction throughout the battery charging process. During battery discharge, the plated species may be ionized via additional electrochemical reactions, thereby becoming soluble in the electrolyte. In a hybrid redox flow battery system, the charge capacity of the redox flow battery (e.g., the maximum amount of energy stored) may be limited by the amount of metal plated during battery charging, and may accordingly depend on the efficiency of the electroplating system and the volume and surface area available for electroplating.

[0020] In some instances, electrolysis imbalance in redox flow batteries can be caused by a number of side reactions competing with the desired redox chemistry, including hydrogen (H2) production reactions such as proton reduction and iron corrosion:

[0021]

[0022] and excess ferric iron (Fe 3+ ) caused by charge imbalance:

[0023]

[0024] The reactions of equations (1) to (3) may limit iron plating and thereby reduce the overall battery capacity. To address such imbalances, electrolyte rebalancing can be used to achieve reduction of Fe by a single redox reaction. 3+ and elimination of excess H2:

[0025] Fe 3+ +1 / 2H2→Fe 2+ +H + (Electrolyte Rebalance) (4)

[0026] As described by the examples herein, sufficient Fe 3+ The reduction rate can be reliably achieved by rebalancing the battery cells, such as Figure 2A and 2B An exemplary rebalanced battery cell includes a stack of internally shorted electrode assemblies, such as Figure 3 An exemplary electrode assembly of . Figure 4A and 4B A first H2 flow pattern in a rebalanced cell is depicted, where H2 flows through the negative electrode and toward the hydrogen outlet port. Figure 5A and 5B A second H2 flow pattern in a rebalanced cell is depicted, where the hydrogen outlet port is closed and H2 flows through the positive electrode and toward the hydrogen release port. Figure 6-9 A rebalanced battery cell system is described in which different ports of series-connected rebalanced battery cells are fluidly connected to achieve different flow patterns. Fig.10 An exemplary method of operating a rebalanced battery cell system is depicted. As described herein, a series flow connection means that the inlet of a first device and the outlet of a second device are connected together. Conversely, a parallel flow connection means that the inlets of the two devices are connected to each other, and the outlets of the two devices are similarly connected to each other.

[0027] like Figure 1 As shown, in a redox flow battery system 10 having a redox flow battery 11, the negative electrode 26 may be referred to as a plating electrode, and the positive electrode 28 may be referred to as a redox electrode. The negative electrolyte within the plating side (e.g., negative electrode compartment 20) of the redox flow battery cell 18 may be referred to as a plating electrolyte, and the positive electrolyte on the redox side (e.g., positive electrode compartment 22) of the redox flow battery cell 18 may be referred to as a redox electrolyte.

[0028] "Anode" refers to an electrode where an electroactive material loses electrons, and "cathode" refers to an electrode where an electroactive material gains electrons. During battery charging, the negative electrolyte gains electrons at the negative electrode 26, and the negative electrode 26 is the cathode of the electrochemical reaction. During battery discharge, the negative electrolyte loses electrons, and the negative electrode 26 is the anode of the electrochemical reaction. Alternatively, during battery discharge, the negative electrolyte and the negative electrode 26 may be referred to as the anode electrolyte and the anode of the electrochemical reaction, respectively, while the positive electrolyte and the positive electrode 28 may be referred to as the cathode electrolyte and the cathode of the electrochemical reaction, respectively. During battery charging, the negative electrolyte and the negative electrode 26 may be referred to as the cathode electrolyte and the cathode of the electrochemical reaction, respectively, while the positive electrolyte and the positive electrode 28 may be referred to as the anode electrolyte and the anode of the electrochemical reaction, respectively. For simplicity, the terms "positive" and "negative" as used herein are used to refer to electrodes, electrolytes, and electrode compartments in a redox flow battery system.

[0029] An example of a hybrid redox flow battery is an all-iron redox flow battery (IFB), in which the electrolyte includes iron ions in the form of an iron salt (e.g., FeCl2, FeCl3, etc.), and in which the negative electrode 26 includes metallic iron. For example, at the negative electrode 26, divalent iron (Fe 2+ ) gains two electrons during battery charging and acts as iron metal (Fe 0 ) is electroplated onto the negative electrode 26, and Fe 0 During battery discharge, it loses two electrons and redissolves into Fe 2+ At the positive electrode 28, Fe 2+ During battery charging, it loses electrons to form ferric iron (Fe 3+ ), and Fe 3+ During battery discharge, electrons are gained to form Fe 2+ The electrochemical reactions are summarized in equations (5) and (6), where the forward reaction (from left to right) indicates the electrochemical reaction during battery charging, and the reverse reaction (from right to left) indicates the electrochemical reaction during battery discharging:

[0030]

[0031] As discussed above, the negative electrolyte used in IFBs can provide sufficient amounts of Fe 2+ , so that during battery charging, Fe 2- can accept two electrons from the negative electrode 26 to form Fe 0 During battery discharge, the electroplated Fe 0 May lose two electrons, thus ionizing to Fe 2+and dissolves back into the electrolyte. The equilibrium potential of the above reaction is -0.44 V, and thus this reaction provides the negative terminal for the desired system. On the positive side of the IFB, the electrolyte can provide Fe during battery charging. 2- , which loses electrons and oxidizes to Fe 3+ During battery discharge, the Fe supplied by the electrolyte 3+ By absorbing electrons supplied from the positive electrode 28, it becomes Fe 2+ The equilibrium potential for this reaction is +0.77 V, creating a positive terminal for the desired system.

[0032] Compared to other battery types that utilize non-regenerative electrolytes, IFBs can provide the ability to charge and recharge the electrolyte therein. Charging can be achieved by applying a current across electrodes 26 and 28 through terminals 40 and 42, respectively. Negative electrode 26 can be electrically coupled to the negative side of a voltage source through terminal 40, so that electrons can be transferred through positive electrode 28 to the negative electrolyte (e.g., when Fe in the positive electrolyte in positive electrode compartment 22 is 2+ Oxidized to Fe 3+ The electrons provided to the negative electrode 26 can reduce Fe in the negative electrode electrolyte. 2+ To form Fe at the (electroplating) substrate 0 , so that Fe 2+ Electroplating onto the negative electrode 26 .

[0033] When Fe 0 The negative electrode electrolyte remains available for oxidation, and Fe 3+ Discharge can be continued while the positive electrolyte remains available for reduction. As an example, additional Fe can be provided by an external source, such as an external positive electrolyte chamber 52, by increasing the concentration or volume of the positive electrolyte in the positive electrode compartment 22 side of the redox flow battery cell 18. 3+ ions to maintain Fe 3+ More commonly, during discharge, Fe 0 Availability of Fe may be an issue in IFB systems where the Fe available for discharge 0 The charge capacity may be proportional to the surface area and volume of the negative electrode substrate and the electroplating efficiency. 2+ As an example, additional Fe may be provided by means of an external source, such as an external negative electrode electrolyte chamber 50. 2+ ions to increase the concentration or volume of the negative electrolyte on the negative electrode compartment 20 side of the redox flow battery cell 18 to maintain the Fe 2+ availability.

[0034] In an IFB, the positive electrolyte may include ferrous iron, ferric iron, ferric iron complexes, or any combination thereof, while the negative electrolyte may include ferrous iron or ferrous iron complexes, depending on the state of charge (SOC) of the IFB system. As previously mentioned, utilizing iron ions in both the negative and positive electrolytes may allow the same electrolyte species to be utilized on both sides of the redox flow battery cell 18, which may reduce electrolyte cross-contamination and may improve the efficiency of the IFB system, thereby resulting in fewer electrolyte replacements compared to other redox flow battery systems.

[0035] Efficiency loss in IFB may be caused by electrolyte passing through separator 24 (e.g., ion exchange membrane barrier, microporous membrane, etc.). For example, Fe 3+ Ions can pass through Fe 3+ The ion concentration gradient and the electrophoretic force across the separator 24 drive the Fe 3+ Ions penetrate the separator 24 and pass through the negative electrode compartment 20, possibly resulting in a loss of coulombic efficiency. 3+ Ions passing from the low pH redox side (e.g., the more acidic positive electrode compartment 22) to the high pH plating side (e.g., the less acidic negative electrode compartment 20) may result in the precipitation of Fe(OH)3. Precipitation of Fe(OH)3 may degrade the separator 24 and cause permanent battery performance and efficiency losses. For example, Fe(OH)3 precipitates may chemically contaminate the organic functional groups of the ion exchange membrane, or physically block the micropores of the ion exchange membrane. In either case, the membrane ohmic resistance may increase over time and battery performance may deteriorate due to the Fe(OH)3 precipitates. The precipitates can be removed by washing the IFB with acid, but the ongoing maintenance and downtime may be detrimental to commercial battery applications. In addition, washing may depend on regular preparation of the electrolyte, contributing to additional processing costs and complexity. Alternatively, the addition of specific organic acids to the positive and negative electrolytes in response to changes in electrolyte pH can mitigate precipitate formation during battery charge and discharge cycles without increasing overall cost. Additionally, achieving inhibition of Fe 3+ Ion exchange membrane barriers can also mitigate fouling.

[0036] Additional Coulombic efficiency loss may be due to H + The reduction of (eg, protons) and subsequent formation of H 2 results from the reaction of the protons in the negative electrode compartment 20 with the electrons supplied at the electroplated iron metal of the negative electrode 26 to form H 2 .

[0037] IFB electrolytes (e.g., FeCl2, FeCl3, FeSO4, Fe2(SO4)3, etc.) are readily available and can be produced at low cost. In one example, the IFB electrolyte can be made of ferrous chloride (FeCl 2) , potassium chloride (KCl), manganese (II) chloride (MnCl2) and boric acid (H3BO3). IFB electrolytes can provide higher recycling value because the same electrolyte can be used for the negative electrode electrolyte and the positive electrode electrolyte, thus reducing cross-contamination problems compared to other systems. In addition, due to the electronic configuration of iron, iron can be solidified into a substantially uniform solid structure during electroplating of iron onto the negative electrode substrate. For zinc and other metals commonly used in hybrid redox batteries, solid dendrite-like structures may be formed during electroplating. Compared with other redox flow batteries, the stable electrode morphology of the IFB system can improve the efficiency of the battery. Still further, compared with other redox flow battery electrolytes, iron redox flow batteries can reduce the use of toxic raw materials and can operate at a relatively neutral pH. Therefore, compared with all other advanced redox flow battery systems currently in production, the IFB system can reduce environmental hazards.

[0038] Continue to refer Figure 1 , a schematic illustration of a redox flow battery system 10 is shown. The redox flow battery system 10 may include a redox flow battery cell 18 fluidly coupled to an integrated multi-chamber electrolyte storage tank 110. The redox flow battery cell 18 may include a negative electrode compartment 20, a separator 24, and a positive electrode compartment 22. The separator 24 may include an electrically insulating ion-conducting barrier that prevents substantial mixing of the positive electrode electrolyte with the negative electrode electrolyte while allowing specific ions to be conducted therethrough. For example, and as discussed above, the separator 24 may include an ion exchange membrane and / or a microporous membrane.

[0039] Negative electrode compartment 20 may include negative electrode 26, and the negative electrolyte may include an electroactive material. Positive electrode compartment 22 may include positive electrode 28, and the positive electrolyte may include an electroactive material. In some examples, multiple redox flow battery cells 18 may be combined in series or in parallel to produce a higher voltage or current in the redox flow battery system 10.

[0040] Figure 1 Further shown are negative electrolyte pump 30 and positive electrolyte pump 32, both of which are used to pump electrolyte solution through the redox flow battery system 10. The electrolyte is stored in one or more tanks external to the battery cell and is pumped through the negative electrode compartment 20 side and the positive electrode compartment 22 side of the redox flow battery cell 18 by the negative electrolyte pump 30 and the positive electrolyte pump 32, respectively.

[0041] The redox flow battery system 10 may also include a first bipolar plate 36 and a second bipolar plate 38, each of which is positioned along a rearward-facing side of the negative electrode 26 and the positive electrode 28, respectively, such as opposite to the side facing the separator 24. The first bipolar plate 36 may be in contact with the negative electrode 26, and the second bipolar plate 38 may be in contact with the positive electrode 28. However, in other examples, the bipolar plates 36 and 38 may be arranged proximate to the electrodes 26 and 28 but spaced apart from the electrodes, and housed within the respective electrode compartments 20 and 22. In either case, the bipolar plates 36 and 38 may be electrically coupled to the terminals 40 and 42, respectively, by direct contact therewith or through the negative electrode 26 and the positive electrode 28, respectively.

[0042] The IFB electrolyte may be delivered to the reaction sites at the negative electrode 26 and the positive electrode 28 by the first bipolar plate 36 and the second bipolar plate 38 due to the conductive properties of the materials of the bipolar plates 36 and 38. The electrolyte flow may also be assisted by the negative electrolyte pump 30 and the positive electrolyte pump 32, thereby promoting forced convection through the redox flow battery cell 18. The reacted electrochemical species may also be directed away from the reaction sites by a combination of forced convection and the presence of the first bipolar plate 36 and the second bipolar plate 38.

[0043] like Figure 1 As shown, the redox flow battery cell 18 may further include a negative battery terminal 40 and a positive battery terminal 42. When a charging current is applied to the battery terminals 40 and 42, the positive electrolyte may be oxidized (lose one or more electrons) at the positive electrode 28, and the negative electrolyte may be reduced (gain one or more electrons) at the negative electrode 26. During battery discharge, a reverse redox reaction may occur at the electrodes 26 and 28. In other words, the positive electrolyte may be reduced (gain one or more electrons) at the positive electrode 28, and the negative electrolyte may be oxidized (lose one or more electrons) at the negative electrode 26. The potential difference across the cell may be maintained by the electrochemical redox reactions in the positive electrode compartment 22 and the negative electrode compartment 20, and a current may be induced through the current collector while the reaction continues. The amount of energy stored by the redox battery may be limited by the amount of electroactive material available for discharge in the electrolyte, which depends on the total volume of the electrolyte and the solubility of the electroactive material.

[0044] The redox flow battery system 10 may further include an integrated multi-chamber electrolyte tank 110. The multi-chamber electrolyte tank 110 may be separated by a separator 98. The separator 98 may form multiple chambers within the multi-chamber electrolyte tank 110 so that both the positive electrolyte and the negative electrolyte may be included in a single tank. The negative electrolyte chamber 50 contains a negative electrolyte including an electroactive material, and the positive electrolyte chamber 52 contains a positive electrolyte including an electroactive material. The separator 98 may be positioned within the multi-chamber electrolyte tank 110 to produce a desired volume ratio between the negative electrolyte chamber 50 and the positive electrolyte chamber 52. In one example, the separator 98 may be positioned to set the volume ratio of the negative electrolyte chamber 50 to the positive electrolyte chamber 52 according to the stoichiometric ratio between the negative redox reaction and the positive redox reaction. Figure 1 Further shown is a fill level 112 of the multi-chamber electrolyte storage tank 110 , which may indicate the liquid level in each tank compartment.

[0045] Figure 1 Also shown is a gas headspace 90 located above the fill level 112 of the negative electrolyte chamber 50, and a gas headspace 92 located above the fill level 112 of the positive electrolyte chamber 52. The gas headspace 92 can be used to store H2 generated by the operation of the redox flow battery (e.g., due to proton reduction and iron corrosion side reactions) and transported to the multi-chamber electrolyte storage tank 110 along with the return electrolyte from the redox flow battery cell 18. The H2 can spontaneously separate at the gas-liquid interface (e.g., fill level 112) within the multi-chamber electrolyte storage tank 110, thereby eliminating an additional gas-liquid separator as part of the redox flow battery system 10. Once separated from the electrolyte, the H2 can fill the gas headspaces 90 and 92. Therefore, the stored H2 can help scavenge other gases from the multi-chamber electrolyte storage tank 110, thereby acting as an inert gas blanket for reducing oxidation of electrolyte species, which can help reduce redox flow battery capacity loss. In this way, the use of the integrated multi-chamber electrolyte tank 110 can eliminate the separate negative electrolyte tank and positive electrolyte tank, hydrogen tank and gas-liquid separator commonly used in conventional redox flow battery systems, thereby simplifying the system design, reducing the physical footprint of the redox flow battery system 10, and reducing the system cost.

[0046] Figure 1Also shown is an overflow hole 96 which may form an opening in the separator 98 between the gas head spaces 90 and 92 and may provide a means of equalizing the gas pressure between the chambers 50 and 52. The overflow hole 96 may be positioned at a threshold height above the fill height 112. The overflow hole 96 may further enable the ability to self-balance the electrolyte in each of the negative and positive electrolyte chambers 50 and 52 in the event of a battery swap. In the case of an all-iron redox flow battery system, the same electrolyte (Fe 2 O 2 ) is used in both the negative and positive electrode compartments 20 and 22. 2+ ), so overflow of electrolyte between the negative electrolyte chamber 50 and the positive electrolyte chamber 52 may reduce the overall system efficiency, but the overall electrolyte composition, battery module performance and battery module capacity can be maintained.

[0047] Flange fittings may be used for all plumbing connections to and from the inlet and outlet of the multi-chamber electrolyte storage tank 110 to maintain a continuous pressurized state without leaks. The multi-chamber electrolyte storage tank 110 may include at least one outlet from each of the negative electrolyte chamber 50 and the positive electrolyte chamber 52, and at least one inlet to each of the negative electrolyte chamber 50 and the positive electrolyte chamber 52. In addition, one or more outlet connections may be provided from the gas headspaces 90 and 92 for directing H2 to the rebalance cells 80 and 82, such that the rebalance cells 80 and 82 may be fluidly coupled to the gas headspaces 90 and 92, respectively. Hydrogen may be circulated through the rebalance cells 80 and 82 to maintain electrolyte health and battery capacity. The hydrogen flow architecture is described herein with respect to Figure 2A-9 Extensions.

[0048] although Figure 1 1 , but the integrated multi-chamber electrolyte tank 110 may further include one or more heaters thermally coupled to each of the negative electrolyte chamber 50 and the positive electrolyte chamber 52. In an alternative example, only one of the negative electrolyte chamber 50 and the positive electrolyte chamber 52 may include one or more heaters. In the case where only the positive electrolyte chamber 52 includes one or more heaters, the negative electrolyte may be heated by transferring the heat generated at the redox flow battery cell 18 to the negative electrolyte. In this way, the redox flow battery cell 18 can heat and promote temperature regulation of the negative electrolyte. One or more heaters may be actuated by the controller 88 to independently or jointly regulate the temperature of the negative electrolyte chamber 50 and the positive electrolyte chamber 52. For example, in response to the electrolyte temperature decreasing below a threshold temperature, the controller 88 may increase the power supplied to the one or more heaters so that the heat flux to the electrolyte can be increased. The electrolyte temperature may be indicated by one or more temperature sensors, such as sensors 60 and 62, installed at the multi-chamber electrolyte tank 110.

[0049] As an example, one or more heaters may include a coil-type heater or other immersion heater immersed in the electrolyte, or a surface cover type heater that transfers heat by conduction through the walls of the negative electrolyte chamber 50 and the positive electrolyte chamber 52 to heat the fluid therein. Other known types of tank heaters may be employed without departing from the scope of the present disclosure. In addition, the controller 88 may deactivate one or more heaters in the negative electrolyte chamber 50 and the positive electrolyte chamber 52 in response to the liquid level decreasing below the solid fill threshold level. In other words, in some examples, the controller 88 may activate one or more heaters in the negative electrolyte chamber 50 and the positive electrolyte chamber 52 only in response to the liquid level increasing above the solid fill threshold level. In this way, it is possible to avoid activating one or more heaters in the case where there is not enough liquid in the negative electrolyte chamber 50 and / or the positive electrolyte chamber 52, thereby reducing the risk of overheating or burning of the heaters.

[0050] Still further, one or more inlet connections may be provided to each of the negative electrolyte chamber 50 and the positive electrolyte chamber 52 from the on-site hydration system. In this way, the on-site hydration system may facilitate the commissioning of the redox flow battery system 10, including installation, filling, and hydration of the redox flow battery system 10 at the final use location. In addition, before commissioning the redox flow battery system 10 at the final use location, the redox flow battery system 10 may be dry assembled at a battery manufacturing facility different from the final use location without filling and hydrating the redox flow battery system 10, and then the redox flow battery system 10 may be delivered to the final use location. In one example, the final use location may correspond to the location where the redox flow battery system 10 will be installed and used for on-site energy storage. In other words, the redox flow battery system 10 may be designed so that once installed and hydrated at the final use location, the location of the redox flow battery system 10 may become fixed, and the redox flow battery system 10 may no longer be considered a portable, dry system. Therefore, from the end user's perspective, the dry, portable redox flow battery system 10 can be delivered on site, after which the redox flow battery system 10 can be installed, hydrated, and commissioned. Before hydration, the redox flow battery system 10 can be referred to as a dry, portable system, and the redox flow battery system 10 does not contain or is free of water and wet electrolyte. Once hydrated, the redox flow battery system 10 can be referred to as a wet, non-portable system, and the redox flow battery system 10 includes a wet electrolyte.

[0051] Figure 1As further shown in FIG. 1 , the electrolyte solution primarily stored in the multi-chamber electrolyte storage tank 110 can be pumped through the entire redox flow battery system 10 by the negative electrolyte pump 30 and the positive electrolyte pump 32. The electrolyte stored in the negative electrolyte chamber 50 can be pumped through the negative electrode compartment side of the redox flow battery cell 18 by the negative electrolyte pump 30, and the electrolyte stored in the positive electrolyte chamber 52 can be pumped through the positive electrode compartment 22 side of the redox flow battery cell 18 by the positive electrolyte pump 32.

[0052] Electrolyte rebalancing cells 80 and 82 (e.g., reactors) can be connected in series or in parallel with the recirculating flow paths of the electrolyte at the negative and positive sides of the redox flow battery cells 18 in the redox flow battery system 10, respectively. One or more rebalancing reactors can be connected in series with the recirculating flow paths of the electrolyte at the negative and positive sides of the battery, and other rebalancing reactors can be connected in parallel to achieve redundancy (e.g., the rebalancing reactor can be served without destroying the battery and rebalancing operations) and enhance rebalancing capabilities. In one example, the electrolyte rebalancing cells 80 and 82 can be placed in the return paths leading from the negative electrode compartment 20 and the positive electrode compartment 22 to the negative electrolyte chamber 50 and the positive electrolyte chamber 52, respectively. The electrolyte rebalancing cells 80 and 82 can be used to rebalance the electrolyte charge imbalance that occurs in the redox flow battery system 10 due to side reactions, ion exchange, etc., as described herein.

[0053] In some examples, one or both of the rebalance reactors 80 and 82 may include a trickle bed reactor, in which H2 and the (liquid) electrolyte may contact at the catalyst surface in the packed bed to perform the electrolyte rebalance reaction. Additionally or alternatively, one or both of the rebalance cells 80 and 82 may have a catalyst bed configured in a jelly roll configuration. In additional or alternative examples, one or both of the rebalance cells 80 and 82 may include a flow-through reactor capable of contacting H2 and the electrolyte and performing the electrolyte rebalance reaction without a packed catalyst bed. However, the lower Fe during electrolyte rebalance 3+ Reduction rates (eg, on the order of about 1-3 mol / m2 / hr) may preclude implementation of such rebalance reactor configurations in higher performance applications.

[0054] In other examples, one or both of the rebalance cells 80 and 82 may include a fuel cell cell, wherein H2 and the electrolyte may contact at a catalyst surface to perform an electrolyte rebalance reaction, and wherein a closed circuit may be formed by directing current from the fuel cell cell through an external load. However, in some cases, reverse current spikes (e.g., transient increases in reverse current, where "reverse current" may be used herein to refer to any current traveling along an electrical path in a direction opposite to the intended direction (i.e., opposite to the "forward direction")) in such fuel cell cells may be unavoidable, thereby gradually compromising the reliability of such rebalance reaction configurations.

[0055] In order to increase the Fe without sacrificing the overall reliability of the rebalancing cells 80 and 82 3+ Reduction rate, the embodiment of the present disclosure provides a rebalancing battery cell, such as Figure 2A and 2B A rebalanced battery cell comprising a stack of internally shorted electrode assemblies, such as Figure 3 The electrode assembly is configured to drive the H2 and electrolyte to react at the catalyst surface through a combination of internal current, convection, gravity feeding, and capillary action. In the embodiments described herein, the electrode assemblies in the stack of internally shorted electrode assemblies can be referred to as "internally shorted" because no current can be directed away from the stack of internally shorted electrode assemblies during operation of rebalancing the battery cell. Such internal electrical shorting can reduce or eliminate reverse current spikes while greatly increasing the Fe 3+ The reduction rate is increased (e.g., to as high as about 50-70 mol / m2 hour) and incidentally reduces the rate of side reactions (e.g., the rate of the reactions of equations (1)-(3)). Further, each electrode assembly in the stack of internally shorted electrode assemblies can be electrically decoupled from each other electrode assembly in the stack of internally shorted electrode assemblies, such that degradation of the stack of internally shorted electrode assemblies during a current spike at one electrode assembly can be limited thereto (e.g., reverse current cannot be driven from one electrode assembly through the other electrode assemblies). In such cases, a single degraded electrode assembly can be easily removed from the stack of internally shorted electrode assemblies and replaced with a non-degraded electrode assembly.

[0056] To achieve an internal short circuit, each electrode assembly in the stack of internal shorting electrode assemblies may include an interfacing pair of positive and negative electrodes (e.g., configured to be in coplanar contact with each other so as to be continuously conductive). As used herein, a pair of first and second components (e.g., a positive electrode and a negative electrode of an electrode assembly) may be described as being "interfacing" with each other when the first component is arranged adjacent to the second component, such that the first component and the second component are in coplanar contact with each other (where "adjacent" is used herein to refer to any two components with no intermediate components therebetween). Further, as used herein, when describing the conductivity of a plurality of electrodes, "continuously" may refer to an electrical path having virtually zero or nearly zero resistance at any coplanar interface of the plurality of electrodes.

[0057] In an exemplary embodiment, the (positive) rebalanced cell 82 may be a stacked rebalanced cell including an internal shorted electrode assembly. A rebalanced positive electrolyte may be desirable with a higher Fe 3- reduction rate, since a large amount of Fe may be generated at the positive electrode 28 during battery charging 3+ (See Equation (6)). In additional or alternative embodiments, the (negative) rebalance reactor 80 may have a similar configuration [Fe may be generated at the negative electrode 26 during iron electroplating oxidation 3+ (See equation (3))].

[0058] During operation of the redox flow battery system 10, sensors and detectors may monitor and control the chemical properties of the electrolyte, such as electrolyte pH, concentration, SOC, etc. For example, Figure 1 As shown, sensors 62 and 60 can be positioned to monitor the positive electrolyte and negative electrolyte conditions at positive electrolyte chamber 52 and negative electrolyte chamber 50, respectively. In another example, sensors 62 and 60 can each include one or more electrolyte level sensors to indicate the level of electrolyte in positive electrolyte chamber 52 and negative electrolyte chamber 50, respectively. As another example, also as Figure 1 As shown, sensors 72 and 70 can monitor the positive electrolyte and negative electrolyte conditions at the positive electrode compartment 22 and the negative electrode compartment 20, respectively. Sensors 72 and 70 can be pH probes, optical probes, pressure sensors, voltage sensors, etc. It should be understood that sensors can be positioned at other locations throughout the redox flow battery system 10 to monitor electrolyte chemistry and other properties.

[0059] For example, a sensor may be positioned in an external acid tank to monitor the acid volume or pH of the external acid tank, wherein the acid from the external acid tank may be supplied to the redox flow battery system 10 by an external pump to reduce the formation of precipitates in the electrolyte. Additional external tanks and sensors may be installed for supplying other additives to the redox flow battery system 10. For example, various sensors including temperature, conductivity, and level sensors of a field hydration system may transmit signals to a controller 88. In addition, during the hydration process of the redox flow battery system 10, the controller 88 may send signals to actuators such as valves and pumps of the field hydration system. As an example, sensor information may be transmitted to the controller 88, which in turn may actuate pumps 30 and 32 to control electrolyte flow through the redox flow battery unit 18, or perform other control functions. In this way, the controller 88 may respond to one or a combination of sensors and detectors.

[0060] The redox flow battery system 10 may further include a H2 source. In one example, the H2 source may include a separate dedicated hydrogen storage tank. Figure 1 In an example, H2 can be stored in and supplied from the integrated multi-chamber electrolyte tank 110. The integrated multi-chamber electrolyte tank 110 can supply additional H2 to the positive electrolyte chamber 52 and the negative electrolyte chamber 50. The integrated multi-chamber electrolyte tank 110 can alternately supply additional H2 to the inlets of the electrolyte rebalancing cells 80 and 82. As an example, a mass flow meter or other flow control device (which can be controlled by the controller 88) can regulate the flow of H2 from the integrated multi-chamber electrolyte tank 110. The integrated multi-chamber electrolyte tank 110 can supplement the H2 produced in the redox flow battery system 10. For example, when a gas leak is detected in the redox flow battery system 10 or the reduction reaction rate at a low hydrogen partial pressure (e.g., Fe 3+ When the reduction rate (reduction rate) is too low, H2 can be supplied from the integrated multi-chamber electrolyte tank 110 to rebalance the SOC of the electroactive materials in the positive and negative electrolytes. As an example, the controller 88 can supply H2 from the integrated multi-chamber electrolyte tank 110 in response to a measured pH change or in response to a measured SOC change of the electrolyte or the electroactive material.

[0061] For example, an increase in the pH value of the negative electrolyte chamber 50 or the negative electrode compartment 20 may indicate that H2 is leaking from the redox flow battery system 10 and / or the reaction rate is too slow at the available hydrogen partial pressure, and the controller 88 may increase the supply of H2 from the integrated multi-chamber electrolyte tank 110 to the redox flow battery system 10 in response to the pH increase. As another example, the controller 88 may supply H2 from the integrated multi-chamber electrolyte tank 110 in response to a pH change, where the pH increases above a first threshold pH or decreases above a second threshold pH. In the case of an IFB, the controller 88 may supply additional H2 to increase the Fe 3+ The reduction rate of ions and the generation rate of protons can be increased, thereby reducing the pH of the positive electrolyte. In addition, the pH of the negative electrolyte can be adjusted by the Fe exchanged from the positive electrolyte to the negative electrolyte. 3+ The hydrogen reduction of ions is reduced by protons generated on the positive electrode side and exchanged to the negative electrode electrolyte due to the proton concentration gradient and electrophoretic force. In this way, the pH of the negative electrode electrolyte can be maintained within a stable range while reducing the Fe (exchanged from the positive electrode compartment 22). 3+ Risk of ion precipitation as Fe(OH)3.

[0062] Other control schemes may be implemented to control the rate of H2 supply from the integrated multi-chamber electrolyte storage tank 110 in response to changes in electrolyte pH or changes in electrolyte SOC detected by other sensors such as an oxygen reduction potential (ORP) meter or an optical sensor. Still further, the pH or SOC change that triggers the action of the controller 88 may be based on the rate of change or change measured over a certain period of time. The time period of the rate of change may be predetermined or adjusted based on the time constant of the redox flow battery system 10. For example, if the recirculation rate is high, the time period may be reduced, and local changes in concentration (e.g., due to side reactions or gas leaks) may be measured quickly because the time constant may be small.

[0063] The controller 88 may further implement a control scheme based on the operating mode of the redox flow battery system 10. For example, and as described below with reference to Fig.10 As discussed in detail, while controlling the flow of H2 to the rebalancing cells 80 and 82 as described above, during the charging and discharging of the redox flow battery cell 18, the controller 88 can control the flow of the negative electrolyte and the positive electrolyte to the rebalancing cells 80 and 82, respectively, so as to simultaneously remove excess H2 and reduce Fe in the redox flow battery system 10. 3+ After the electrolyte is rebalanced, the controller 88 can direct any excess or unreacted H2 along with the rebalanced negative and positive electrolytes (e.g., including a reduced concentration of Fe 3+ and increasing concentrations of Fe2+ ) flows from the rebalanced cells 80 and 82 back into the respective electrolyte chambers 50 and 52 of the multi-chamber electrolyte storage tank 110. Additionally or alternatively, the unreacted H2 may be returned to a separate dedicated hydrogen storage tank.

[0064] As another example, the controller 88 may further control the charging and discharging of the redox flow battery cell 18 so as to cause iron pre-formation at the negative electrode 26 during system conditioning (wherein the system conditioning may include an operating mode to optimize the electrochemical performance of the redox flow battery system 10 outside of battery cycling). That is, during system conditioning, the controller 88 may adjust one or more operating conditions of the redox flow battery system 10 to electroplate iron metal on the negative electrode 26 to increase the battery charge capacity during subsequent battery cycling (thus, iron metal may be pre-formed for battery cycling). In this way, pre-forming iron at the negative electrode 26 and running electrolyte rebalancing during system conditioning can increase the total capacity of the redox flow battery cell 18 during battery cycling by mitigating iron plating losses. As used herein, a battery cycle (also referred to as a "charge cycle") may include alternation between a charge mode and a discharge mode of the redox flow battery system 10.

[0065] It should be understood that all components except the sensors 60 and 62 and the integrated multi-chamber electrolyte tank 110 (and the components included therein) can be considered to be included in the power module 120. Therefore, the redox flow battery system 10 can be described as including a power module 120 that is fluidically coupled to the integrated multi-chamber electrolyte tank 110 and communicatively coupled to the sensors 60 and 62. In some examples, each of the power module 120 and the multi-chamber electrolyte tank 110 can be included in a single housing or packaging so that the redox flow battery system 10 can be housed in a single location as a single unit. It should also be understood that the positive electrolyte, the negative electrolyte, the sensors 60 and 62, the electrolyte rebalancing cells 80 and 82, and the integrated multi-chamber electrolyte tank 110 (and the components included therein) can be considered to be included in the electrolyte subsystem 130. Therefore, the electrolyte subsystem 130 can supply one or more electrolytes to the redox flow battery cell 18 (and the components included therein).

[0066] Reference now Figure 2A and 2B , respectively, showing perspective views, each perspective view depicting a Figure 1 The rebalancing battery cell 202 of the redox flow battery system 10 and the like. In an exemplary embodiment, the rebalancing battery cell 202 may include the following reference Figure 3The stack of electrode assemblies such as the electrode assemblies described in detail can be facilitated by a redox flow battery such as Figure 1 The contact between H2 and the electrolyte in the positive electrode compartment or the negative electrode compartment of the redox flow battery cell 18 drives the electrolyte rebalancing reaction at the catalytic surface of the negative electrode of the stack of the internal shorted electrode assembly. Therefore, the rebalancing battery cell 202 can be Figure 1 One or both of the rebalancing battery cells 80 and 82.

[0067] A collection of reference axes 250 are provided to describe the relative positioning of the components shown and for use in Figure 2A-5B For comparison between the views of FIG. 1 and FIG. 2 , axis 250 indicates the x-axis, y-axis, and z-axis. Figure 2A and 2B As further shown by the dashed lines in , the additional axis g can be parallel to the direction of gravity (e.g., in the positive direction along the axis g) and the vertical direction (e.g., in the negative direction along the axis g and opposite to the direction of gravity).

[0068] The number of rebalancing cells 202 included in the redox flow battery system and the number of electrode assemblies included in the stack of internal shorted electrode assemblies are not particularly limited and can be increased to accommodate applications corresponding to higher performance. For example, a 75kW redox flow battery system may include two rebalancing cells 202, the rebalancing cells including a stack of 20 electrode assemblies (e.g., a stack of 19 bipolar assemblies with 2 end plates positioned at opposite ends of the stack).

[0069] As shown, the stack of internal shorted electrode assemblies can be removably enclosed within an outer battery cell housing (e.g., a shell) 204. Thus, in some examples, the battery cell housing 204 can include a top cover that is removably attached to the housing base so that the top cover can be temporarily removed to replace or troubleshoot one or more electrode assemblies in the stack of internal shorted electrode assemblies. In additional or alternative examples, Figure 2A and 2B The battery cell housing 204, depicted as a rectangular prism in FIG. 1 , can be molded to be a clearance fit with other components of the redox flow battery system so that the rebalanced battery cell 202 can be in coplanar contact with such components. In some examples, the battery cell housing 204 can be constructed of a material with low electrical conductivity, such as plastic or other polymers, to reduce undesirable shorting events.

[0070] The battery cell housing 204 may also be configured to include openings or cavities for interfacing components of the rebalancing battery cells 202. For example, the battery cell housing 204 may include a plurality of inlet ports and outlet ports configured to be fluidly coupled to other components of the redox flow battery system. In one example, and as shown, the plurality of inlet ports and outlet ports may include polypropylene (PP) flange fittings welded to PP pipes.

[0071] In an exemplary embodiment, the plurality of inlet ports and outlet ports may include an electrolyte inlet port 206 for flowing electrolyte into the battery cell housing 204, and an electrolyte outlet port 208 for draining electrolyte from the battery cell housing 204. The electrolyte inlet port and electrolyte outlet port may be referred to as a positive inlet port and a positive outlet port due to the battery cell chemistry.

[0072] In one example, the electrolyte inlet port 206 can be positioned on the upper half of the battery cell housing 204, and the electrolyte outlet port 208 can be positioned on the lower half of the battery cell housing 204 (where the upper and lower halves of the battery cell housing 204 are separated along the z-axis by a plane parallel to each of the x-axis and the y-axis). Thus, the electrolyte outlet port 208 can be positioned lower than the electrolyte inlet port 206 relative to the direction of gravity (e.g., along the axis g).

[0073] Specifically, after the electrolyte enters the cell housing 204 through the electrolyte inlet port 206, the electrolyte can be distributed across the stack of internal shorted electrode assemblies, gravity-fed through the stack of electrode assemblies, wicked through the positive electrode of the stack of internal shorted electrode assemblies (e.g., opposite to the direction of gravity) to cause a cathode half-reaction at the catalytic surface of the negative electrode, and discharged from the cell housing 204 through the electrolyte outlet port 208. To assist in the gravity feeding of the electrolyte and increase its pressure drop, the rebalanced cell 202 can be further tilted or tilted relative to the direction of gravity by an inclined support 220 coupled to the cell housing 204. In some examples, tilting the cell housing 204 in this manner can further assist in the electrolyte discharge of the rebalanced cell 202 (e.g., during an idle mode of the redox flow battery system) and keep the catalytic surface relatively dry (because in some examples, the catalytic surface may corrode after being immersed in the electrolyte for a long enough duration).

[0074] As shown, the inclined support 220 can deflect the battery cell housing 204 at an angle 222, so that the plane of the stacked electrode sheets of the internal short-circuited electrode assembly is inclined at an angle 222 relative to the lower surface on which the inclined support 220 rests. In some examples, the angle 222 (e.g., the angle of the battery cell housing 204 relative to the lower surface) can be between 0° and 30°. In embodiments where the angle 222 is substantially 0°, the rebalancing battery cell 202 can still function, but deflecting the battery cell housing 204 at an angle greater than 0° may cause a greater pressure drop and reduce electrolyte exchange to the negative electrode. In some examples, the angle 222 can be between 2° and 30°. In some examples, the angle 222 can be between 2° and 20°. In one example, the angle 222 can be about 8°. Therefore, the pressure drop of the electrolyte after entering the battery cell housing 204, such as through the electrolyte inlet port 206, can be increased by increasing the angle 222 and reduced by reducing the angle 222.

[0075] Additionally or alternatively, one or more support rails 224 can be coupled to the upper portion of the battery cell housing 204 (eg, opposite the inclined support member 220). Figure 2A As shown in the perspective view of FIG. 2 , one or more support rails 224 can be tilted relative to the battery cell housing 204 at an angle 222, so that the one or more support rails 224 can removably secure the rebalanced battery cell 202 to an upper surface that is above and parallel to the lower surface. In this manner, and based on geometric considerations, the z-axis can be similarly offset relative to the axis g at an angle 222 (e.g., the battery cell housing 204 can be tilted relative to a vertical direction opposite to the direction of gravity at an angle 222, such as Figure 2A and 2B In some examples, the rebalancing cell 202 may be positioned in a vertical direction opposite to the gravity direction in an electrolyte storage tank of the redox flow battery system (e.g., Figure 1 The multi-chamber electrolyte storage tank 110 is above the electrolyte storage tank 110 to further assist in the gravity feeding of electrolyte through the rebalancing battery cell 202.

[0076] As further shown, the electrolyte outlet port 208 may include a plurality of openings in the battery cell housing 204 configured to discharge at least a portion of the electrolyte (each of the plurality of openings includes a PP flange fitting welded to a PP pipe). Figure 2A and 2B, the electrolyte outlet port 208 is shown as including five openings. In this way, the electrolyte can be evenly distributed across the stack of the internal shorting electrode assembly, and can be discharged from the battery cell housing 204 with substantially unimpeded flow ("substantially" can be used as a qualifier meaning "effectively" in this article). In other examples, the electrolyte outlet port 208 may include more than five openings or less than five openings. In one example, the electrolyte outlet port 208 may include a single opening. In additional or alternative examples, the electrolyte outlet port 208 can be positioned below the unit housing 204 relative to the z-axis (e.g., on the face of the battery cell housing 204 facing the negative direction of the z-axis).

[0077] The electrolyte inlet port 206 and the electrolyte outlet port 208 can be positioned on the battery cell housing 204 based on the flow path of the electrolyte through the stack of the internal shorting electrode assembly (e.g., from the electrolyte inlet port 206 to the electrolyte outlet port 208, and including a channel, passage, manifold, plenum, groove, etc. that is fluidly coupled to the electrolyte inlet port 206 and the electrolyte outlet port 208 within the battery cell housing 204). In some examples, and as shown, the electrolyte inlet port 206 and the electrolyte outlet port 208 can be positioned on adjacent sides of the battery cell housing 204 (e.g., faces of the battery cell housing 204 that share a common edge). In other examples, the electrolyte inlet port 206 and the electrolyte outlet port 208 can be positioned on opposite sides of the battery cell housing 204. In other examples, the electrolyte inlet port 206 and the electrolyte outlet port 208 can be positioned on the same side of the battery cell housing 204.

[0078] In some examples, the electrolyte inlet port 206 can be positioned on a side of the battery cell housing 204 facing the negative direction of the x-axis. In additional or alternative examples, the electrolyte inlet port 206 can be positioned on a side of the battery cell housing 204 facing the positive direction of the x-axis. In one example, and as shown, one opening of the electrolyte inlet port 206 can be positioned on a side of the battery cell housing 204 facing the negative direction of the x-axis, and the other opening of the electrolyte inlet port 206 can be positioned on a side of the battery cell housing 204 facing the positive direction of the x-axis.

[0079] In some examples, the plurality of inlet ports and outlet ports may further include a hydrogen inlet port 210 for flowing H2 into the battery cell housing 204 and a hydrogen outlet port 212 for exhausting H2 from the battery cell housing 204 (eg, Figure 2B ). The hydrogen inlet port and the hydrogen outlet port may be referred to as the negative electrode inlet port and the negative electrode outlet port due to the battery cell chemistry.

[0080] In one example, and as shown, each of the hydrogen inlet port 210 and the hydrogen outlet port 212 can be positioned on the lower half of the battery cell housing 204 (e.g., along the z-axis at the lowest electrode assembly in the stack of internal shorted electrode assemblies). In another example, each of the hydrogen inlet port 210 and the hydrogen outlet port 212 can be positioned on the upper half of the battery cell housing 204 (e.g., along the z-axis at the highest electrode assembly in the stack of internal shorted electrode assemblies). In yet another example, the hydrogen inlet port 210 can be positioned on the lower half of the battery cell housing 204, and the hydrogen outlet port 212 can be positioned on the upper half of the battery cell housing 204. In such examples, the hydrogen inlet port 210 can be positioned lower than the hydrogen outlet port 212 relative to the direction of gravity (e.g., along the axis g).

[0081] Specifically, after H2 enters the cell housing 204 through the hydrogen inlet port 210, the H2 can be distributed across and through the stack of internal shorted electrode assemblies by forced convection (e.g., caused by the flow field configuration of the corresponding flow field plates), and decomposed in the anode half-reaction at the catalytic surface of the negative electrode. However, in some examples, excess, unreacted H2 can remain in the rebalanced cell 202 after contacting the catalytic surface. In some examples, at least a portion of the unreacted H2 at the catalytic surface can be transferred to the electrolyte. In such examples, in order to avoid undesirable pressure accumulation and thereby prevent electrolyte accumulation on the positive electrode and concomitant negative electrode electrolyte overflow, the multiple inlet ports and outlet ports can further include a hydrogen release port 214 (such as a hydrogen release port 214) for discharging unreacted H2 from the electrolyte. Figure 2A ). The hydrogen release port 214 may specifically receive hydrogen that has traveled through the electrolyte and thus may be referred to as a positive-side hydrogen release port. The hydrogen release port 214 may specifically receive hydrogen that has traveled through the electrolyte and thus may be referred to as a positive-side hydrogen release port.

[0082] Further, in some examples, the hydrogen outlet port 212 can be configured to exhaust at least a portion of the H2 that has not reacted at the catalytic surface and has not flowed through the negative electrode into the electrolyte. Figures 4A-5B Other aspects of the H2 flow are discussed in more detail.

[0083] The hydrogen inlet port 210 and the hydrogen outlet port 212 can be positioned on the battery cell housing 204 based on the flow path of H2 through the stack of internal shorting electrode assemblies. For example, the flow path can lead from the hydrogen inlet port 210 to the hydrogen outlet port 212 (when included), and include a channel, passage, manifold, boost chamber, etc. located within the battery cell housing 204 and fluidly coupled to the hydrogen inlet port 210 and the hydrogen outlet port 212 (when included). In some examples, and as shown, the hydrogen inlet port 210 and the hydrogen outlet port 212 can be positioned on opposite sides of the battery cell housing 204. In other examples, the hydrogen inlet port 210 and the hydrogen outlet port 212 can be positioned on adjacent sides of the battery cell housing 204. In other examples, the hydrogen inlet port 210 and the hydrogen outlet port 212 can be positioned on the same side of the battery cell housing 204. Further, although the hydrogen inlet port 210 is Figure 2A and 2B The hydrogen outlet port 212 is shown as being located on the side of the battery cell housing 204 facing the negative direction of the x-axis and having the hydrogen outlet port 212 at Figure 2A and 2B 2 is shown as being positioned on a side of the battery cell housing 204 facing the positive direction of the x-axis, but in other examples, the hydrogen inlet port 210 may be positioned on a side of the battery cell housing 204 facing the positive direction of the x-axis and the hydrogen outlet port 212 may be positioned on a side of the battery cell housing 204 facing the negative direction of the x-axis.

[0084] In one example, the hydrogen inlet port 210, the hydrogen outlet port 212, the electrolyte inlet port 206, and the electrolyte outlet port 208 can be positioned in a lateral configuration on the battery cell housing 204. The lateral configuration can include the hydrogen outlet port 212 and the electrolyte inlet port 206 being positioned on different sides (e.g., faces) of the upper half of the battery cell housing 204, and the hydrogen inlet port 210 and the electrolyte outlet port 208 being positioned on different sides of the lower half of the battery cell housing 204.

[0085] In other examples, the hydrogen outlet port 212 may be closed, omitted, or otherwise exhaust H2 that has not reacted at the catalytic surface of the negative electrode and has not flowed through the negative electrode into the electrolyte. However, in such examples, there may still be a hydrogen release port 214 for exhausting unreacted H2 from the electrolyte, and the unreacted H2 may be exhausted from the cell housing 204 only after flowing through the negative electrode into the electrolyte and through the hydrogen release port 214. An exemplary rebalanced cell configuration lacking a hydrogen outlet port 212, whether or not a hydrogen release port 214 is included, may be referred to as a "dead end configuration." In a dead end configuration, substantially all of the H2 may be forced to contact the catalytic surface of the negative electrode, where the H2 may be decomposed by the anode half-reaction and / or the H2 may enter the electrolyte after passing through the negative electrode (e.g., without reacting at its catalytic surface).

[0086] Figure 2A and 2B The rebalanced cell 202 depicted in FIG. 2 can operate with a relatively small pressure gradient between the negative (hydrogen, higher pressure) side and the positive (electrolyte, lower pressure) side of the cell. Gravity and the higher hydrogen pressure prevent electrolyte flooding of the negative channel in the cell due to the internal short circuit of the cell.

[0087] Reference now Figure 3 , showing the use of Figure 2A and 2B202 of the rebalanced battery cell. Thus, the electrode assembly 302 can be shorted internally (e.g., the current flowing through the electrode assembly 302 is not directed through an external load). In an exemplary embodiment, the electrode assembly 302 can be included in a stack of similarly configured electrode assemblies in a battery cell housing to form a rebalanced battery cell. The electrode assembly 302 can include a plate 304 and an activated carbon foam 306, a positive electrode 308 (also referred to as a "cathode" in some examples herein), and a negative electrode 310 (also referred to as an "anode" in some examples herein) stacked thereon in sequence. The electrode assembly 302 can be positioned within the rebalanced battery cell to receive an electrolyte passing through the carbon foam 306, and the electrolyte can enter the pores of the positive electrode 308 from the carbon foam through capillary action and contact the negative electrode 310. The electrode assembly 302 can also be positioned within the rebalanced battery cell to receive H2 through a catalytic surface of the negative electrode 310 that flows across the positive electrode 308. Convection of H2 across the catalytic surface can be aided by a flow field plate interfaced with the catalytic surface. After H2 is decomposed at the catalytic surface via the anodic half-reaction, protons and electrons can flow to the interface of the negative electrode 310 and the positive electrode 308 where ions in the electrolyte can be reduced via the cathodic half-reaction (e.g., Fe 3+ Can be reduced to Fe 2+ ). In this manner, electrode assembly 302 may be configured for fluidly coupling to a redox flow battery that includes a rebalanced cell of electrode assembly 302, such as Figure 1 The electrolyte of the redox flow battery cell 18 is rebalanced.

[0088] In some examples, the board 304 can be made of a material with low electrical conductivity, such as plastic or other polymers, to reduce undesirable shorting events. Figure 2A and 2B The battery cell housing 204 is formed of the same material.

[0089] As shown, the plate 304 may include multiple inlets and outlets passing therethrough. For example, the multiple inlets and outlets may include an electrolyte outlet channel segment 316, a hydrogen inlet channel segment 318a, and a hydrogen outlet channel segment 318b. Specifically, the plate 304 may include an electrolyte outlet channel segment 316 for guiding the electrolyte out of the rebalanced cell, a hydrogen inlet channel segment 318a for guiding H2 into the rebalanced cell and across the negative electrode 310, and a hydrogen outlet channel segment 318b for guiding H2 out of the rebalanced cell. The plate 304 may further include an electrolyte inlet groove 312 for receiving an electrolyte at the electrode assembly 302, the electrolyte inlet groove 312 being fluidly coupled to a plurality of electrolyte inlet passages 314a in a berm 314b positioned adjacent to the carbon foam 306 to distribute the received electrolyte across the carbon foam 306. In some instances, the electrolyte inlet groove 312 may be fluidly coupled to an electrolyte inlet port (e.g., Figure 2A and 2B The electrolyte inlet port 206 of the electrolyte outlet channel segment 316 receives electrolyte (e.g., through the electrolyte inlet channel), and the electrolyte outlet channel segment 316 can be fluidly coupled to the electrolyte outlet port thereof (e.g., Figure 2A and 2B The electrolyte outlet port 208 of the embodiment of the present invention can be used to discharge electrolyte, and the hydrogen inlet channel segment 318a can be used to discharge electrolyte from the hydrogen inlet port (e.g., Figure 2A and 2B The hydrogen inlet port 210 of the embodiment of the present invention receives H2, and the hydrogen outlet channel segment 318b can be connected to the hydrogen outlet port (e.g., Figure 2A and 2B The hydrogen outlet port 212) discharges H2.

[0090] It should be understood that although hydrogen inlet channel segment 318a is described herein as a segment of a hydrogen inlet channel and hydrogen outlet channel segment 318b is described herein as a segment of a hydrogen outlet channel, in other examples, channel segment 318b may be a segment of a hydrogen inlet channel (e.g., for directing H2 into the rebalanced cell and across the negative electrode 310 after receiving H2 from the hydrogen inlet port) and gas inlet channel segment 318a may be a segment of a hydrogen outlet channel (e.g., for directing H2 out of the rebalanced cell by exhausting H2 through the hydrogen outlet port). In other examples, the rebalanced cell may be configured in a dead-end configuration, and no hydrogen outlet port may be fluidly coupled to hydrogen outlet channel segment 318b. In such examples, the hydrogen outlet channel segment 318b may direct H2 back across the negative electrode 310, or the hydrogen outlet channel segment 318b may alternatively be configured as another hydrogen inlet channel segment (e.g., for directing a portion of H2 into the rebalance cell and across the negative electrode 310 after receiving the portion of H2 from the hydrogen inlet port).

[0091] Multiple inlets and outlets can be configured to facilitate electrolyte and H2 flow throughout the rebalanced cell. As an example, the size of each of the hydrogen inlet channel segment 318a and the hydrogen outlet channel segment 318b can be selected to minimize the pressure drop therethrough, thereby assisting in the flow distribution in each electrode assembly 302 of the stack of internal shorted electrode assemblies. As another example, the size of each electrolyte inlet passage 314a and the total number of multiple electrolyte inlet passages 314a relative to the cliff diameter 314b can be selected to cause a relatively small pressure drop to substantially evenly distribute the electrolyte flow. In such examples, the selection of the size of each electrolyte inlet passage 314a and the total number of multiple electrolyte inlet passages 314a can depend on multiple factors specific to a given configuration of the rebalanced cell, such as the size of the electrolyte flow field and the desired electrolyte flow rate.

[0092] In additional or alternative examples, the electrolyte outlet channel segment 316 can be further configured to distribute electrolyte by including a plurality of openings in the electrolyte outlet port. Figure 3In the exploded view of , the electrolyte outlet channel segment 316 is shown as including two openings. In some examples, the number of openings included in the electrolyte outlet channel segment 316 can be equal to the number of openings included in the electrolyte outlet port, so that the openings of the electrolyte outlet channel segment 316 can correspond to the openings of the electrolyte outlet port, respectively. In this way, the electrolyte can be evenly distributed across the electrode assembly 302 and can be discharged from the rebalanced battery cell with substantially unimpeded flow. In other examples, the electrolyte outlet channel segment 316 can include more than two openings or less than two openings (e.g., a single opening).

[0093] Further, when electrode assembly 302 is included in a stack of electrode assemblies, electrolyte outlet channel segment 316, hydrogen inlet channel segment 318a, and hydrogen outlet channel segment 318b may be aligned to form a continuous electrolyte outlet channel, a continuous hydrogen inlet channel, and a continuous hydrogen outlet channel, respectively (e.g., in FIG. Figure 4A , 4B , 5A and 5B, described below). In this way, a stack of electrode assemblies can be formed in a modular manner, whereby any practical number of electrode assemblies 302 can be stacked and included in a rebalanced cell.

[0094] As further shown, a plurality of sealing inserts may be attached (as used herein, "affixed," "affixed," or "affixing" includes, but is not limited to, gluing, attaching, connecting, fastening, joining, linking, or fixing one component to another component by a direct or indirect relationship) or otherwise coupled to the plate 304. As an example, the plurality of sealing inserts may include a hydrogen inlet channel sealing insert 320a and a hydrogen outlet channel sealing insert 320b to induce H2 flow across the negative electrode 310 by mitigating H2 bypass. Specifically, the hydrogen inlet channel sealing insert 320a and the hydrogen outlet channel sealing insert 320b may be attached or otherwise coupled to a side of the plate 304 including the carbon foam 306, the positive electrode 308, and the negative electrode 310 adjacent to the hydrogen inlet channel segment 318a and the hydrogen outlet channel segment 318b, respectively. In some examples, and as described with reference to Figure 4A and 4B Discussed in more detail, the hydrogen inlet channel sealing insert 320a and the hydrogen outlet channel sealing insert 320b can coincide with the xy plane of the negative electrode 310, such that the hydrogen inlet channel sealing insert 320a and the hydrogen outlet channel sealing insert 320b can extend from the attachment or coupling with the plate 304 and partially overlap the positive electrode 308.

[0095] As another example, the plurality of sealing inserts may further include each of a hydrogen inlet channel O-ring 322a and a hydrogen outlet channel O-ring 322b to seal the interface of the hydrogen inlet channel segment 318a with the hydrogen inlet channel segment of another electrode assembly and the interface of the hydrogen outlet channel segment 318b with the hydrogen outlet channel segment of another electrode assembly, respectively. Specifically, the hydrogen inlet channel O-ring 322a and the hydrogen outlet channel O-ring 322b may be attached or otherwise coupled to the plate 304 so as to surround the hydrogen inlet channel segment 318a and the hydrogen outlet channel segment 318b, respectively.

[0096] As another example, the plurality of sealing inserts may further include an overboard O-ring 324 for sealing the interface of the electrode assembly 302 with another electrode assembly at its outer edge. Specifically, the overboard O-ring 324 may be attached or otherwise coupled to the plate 304 so as to surround each of the electrolyte inlet groove 312, the electrolyte inlet passage 314a, the cliff 314b, the electrolyte outlet channel segment 316, the hydrogen inlet channel segment 318a, and the hydrogen outlet channel segment 318b.

[0097] The carbon foam 306 can be positioned in the cavity 326 of the plate 304 between the cliff 314b and the electrolyte outlet channel section 316 along the y-axis and between the hydrogen inlet channel section 318a and the hydrogen outlet channel section 318b along the x-axis. Specifically, the carbon foam 306 can be positioned to form a coplanar contact with one side of the bottom of the cavity 326 of the plate 304. In some examples, the carbon foam 306 can be formed as a continuous integral piece, while in other examples, the carbon foam 306 can be formed as two or more carbon foam sections. In an exemplary embodiment, the carbon foam 306 can be conductive, permeable and porous, thereby providing a distribution field for the electrolyte fed by gravity through multiple electrolyte inlet passages 314a. In some examples, the pore distribution of the carbon foam 306 can be between 10 and 100 PPI. In one example, the pore distribution can be 30 PPI. In an additional or alternative example, the carbon foam 306 may have a permeability between 0.02 and 0.5 mm 2 Thus, each of the pore distribution and permeability (in addition to the overall size) of the carbon foam 306 can be selected to target a relatively small pressure drop and thereby induce convection of electrolyte from the carbon foam 306 into the positive electrode 308. For example, the target pressure drop can be between 2 mm and 3 mm of electrolyte head rise.

[0098] In some examples, the carbon foam 306 can be replaced with a flow field plate configured to transport electrolyte to the positive electrode 308 by convection caused by the flow field configuration of the flow field plate. Specifically, the flow field plate can be fluidly coupled to each of the plurality of electrolyte inlet passages 314a and electrolyte outlet channel segments 316. In one example, the flow field plate can be integrally formed in the plate 304 of the electrode assembly 302, positioned below the positive electrode 308 relative to the z-axis. In other examples, the flow field plate can be a separate, removable component.

[0099] In some examples, the flow field configuration can be an interdigitated flow field configuration, a partially interdigitated flow field configuration, or a serpentine flow field configuration. In some examples, each electrode assembly 302 interfaces with a flow field configuration similar to that of each other electrode assembly 302 (e.g., interdigitated, partially interdigitated, serpentine, etc.). In other examples, depending on Figure 2A and 2B The position of a given electrode assembly 302 in a rebalanced battery cell 202 can provide a plurality of different flow field configurations in the electrode assembly 302 in the stack of electrode assemblies. In this way, electrolyte can be supplied from the electrolyte inlet port (e.g., Figure 2A and 2B The electrolyte inlet ports 206 of the electrode assembly are directed to flow field plates that interface with positive electrodes 308 in the stack of electrode assemblies, respectively, and the flow field plates are configured as an interdigitated flow field configuration, a partially interdigitated flow field configuration, a serpentine flow field configuration, or a combination thereof.

[0100] In certain instances, and as referenced below Figure 4A and 4B Discussed in more detail, in addition to the carbon foam 306 being replaced with a flow field plate (also referred to herein as an "electrolyte flow field plate"), another flow field plate (also referred to herein as a "hydrogen flow field plate") may be interfaced with the negative electrode 310 opposite the positive electrode 308 relative to the z-axis. However, in other examples, an electrolyte flow field plate may be included (e.g., replacing the carbon foam 306) and the hydrogen flow field plate may not be present. In still other examples, a hydrogen flow field plate may be included (e.g., interfaced with the negative electrode 310) and the electrolyte flow field plate may not be present.

[0101] The positive electrode 308 can be positioned in the cavity 326, in coplanar contact with the side of the carbon foam 306 opposite the plate 304 along the z-axis. In an exemplary embodiment, the positive electrode 308 can be a wicking conductive carbon felt, sponge, or mesh that can contact the negative electrode 310 with the electrolyte flowing through the carbon foam 306 by capillary action. Therefore, in some examples, the positive electrode 308 can be conductive and porous (but in such examples, less porous than the carbon foam 306). In one example, when the porosity of the carbon foam 306 can be within a predefined range (e.g., below an upper threshold porosity so as to retain enough solid material to promote wicking upward and into the positive electrode 308, and above a lower threshold porosity so as not to hinder the electrolyte from flowing through the carbon foam 306), the electrolyte can be wicked into the positive electrode 308. In additional or alternative examples, as the porosity of the positive electrode 308 increases, each of the following can be achieved: the absorptivity of the positive electrode 308 can decrease, and the permeability of the positive electrode 308 can increase (e.g., at least until, such as when a threshold porosity of the positive electrode 308 is reached, too little solid material of the positive electrode 308 remains to promote wicking of the electrolyte). In some examples, the hydrophilicity of the surface of the positive electrode 308 may be sufficient to achieve the desired rebalanced battery cell operation (e.g., by promoting thorough electrolyte wetting and thereby forming an ion-conducting medium). In such examples, the overall hydrophilicity of the positive electrode 308 can be increased by coating or treating its surface. Further, although at least some H2 may also enter the positive electrode 308 in addition to a portion of the electrolyte being wicked into the positive electrode 308, the positive electrode 308 can be considered a separator with a large amount of H2 located above the separator and a large amount of electrolyte located below the separator.

[0102] In some examples, each of the positive electrode 308 and the negative electrode 310 can be formed as a continuous integral piece (e.g., not discrete particles or multiple pieces) so that when the electrolyte is brought into contact with H2 at the catalytic surface of the negative electrode 310, interfacial mass transfer losses across the boundary layer membrane can be reduced, thereby promoting ion and proton movement. In contrast, a packed bed configuration including discrete packed catalyst particles can include a mass transfer limiting boundary layer membrane surrounding each individual particle, thereby reducing the mass transfer rate of the electrolyte in the bulk electrolyte to the particle surface.

[0103] The negative electrode 310 can be positioned in the cavity 326 in coplanar contact with the positive electrode 308 on the side opposite to the carbon foam 306 along the z-axis, so that a three-phase contact interface connection can be formed between the (wicked) electrolyte, the catalytic surface of the negative electrode 310 and H2 to provide protons (e.g., H + ) and ions (H3O +) moves through. At the same time, the positive electrode 308 can move into the electrolyte front by providing electrons and reducing the Fe in the electrolyte front. 3+ The conductive path for ions reduces the overall resistance.

[0104] In an exemplary embodiment, the negative electrode 310 may be a porous non-conductive material or a conductive carbon substrate on which a metal catalyst is coated. In some examples, the porous non-conductive material may include polytetrafluoroethylene (PTFE), polypropylene, etc. In some examples, the conductive carbon substrate may include carbon cloth or carbon paper. In some examples, the metal catalyst may include a precious metal catalyst. In some examples, the precious metal catalyst may include Pt. In additional or alternative examples, the precious metal catalyst may include Pd, Rh, Ru, Ir, Ta, or an alloy thereof. In some examples, for cost considerations, a relatively small amount (e.g., 0.2wt% to 0.5wt%) of precious metal catalyst loaded on a conductive carbon substrate may be used. However, in practice, the amount of precious metal catalyst may not be particularly limited and may be selected based on one or more of the desired reaction rate of the rebalanced battery cell and the expected service life of the rebalanced battery cell. In addition, the alloy included in the precious metal catalyst may be used to reduce costs and improve the corrosion stability of the precious metal catalyst. For example, adding 10% Rh to Pt may reduce the corrosion stability of the Fe 3+ The corrosion of Pt is reduced by more than 98%. In other examples, the metal catalyst may include a non-precious metal catalyst (e.g., molybdenum sulfide) selected for stability in ferric iron solutions and other such acidic environments. In one example, the negative electrode 310 may include a 1.0 mg / cm 2 The invention relates to a carbon cloth of Pt and may include a microporous layer bonded with a polytetrafluoroethylene (PTFE) binder (e.g., for hydrophobic purposes). In fact, the addition of a PTFE binder can enhance the durability of rebalancing cell performance over extended durations relative to electrode assemblies formed using other binders.

[0105] In some instances, such as when the noble metal catalyst comprises Pt, immersion of the negative electrode 310 may ultimately result in corrosion of the noble metal catalyst. In other instances, and as described above with reference to Figure 2A and 2BAs discussed in more detail, electrode assembly 302 (along with the stack of electrode assemblies and the entire rebalanced cell) can be tilted or skewed relative to the surface on which the rebalanced cell rests (e.g., the z-axis can be non-parallel to the direction of gravity) so that the precious metal catalyst can remain relatively dry as the electrolyte is drawn through carbon foam 306 by gravity feed toward electrolyte outlet channel segment 316. Thus, in some examples, electrode assembly 302 can be horizontal, or tilted at an angle between 0° and 30° relative to the surface on which the rebalanced cell rests.

[0106] In an exemplary embodiment, the electrode assembly 302 including each of the carbon foam 306, the positive electrode 308, and the negative electrode 310 can be compressed downward along the z-axis, wherein the positive electrode 308 deflects more at a given compression pressure than the carbon foam 306 and the negative electrode 310. Therefore, the depth of the cavity 326 can be selected based on the thickness of the carbon foam 306, the thickness of the positive electrode 308, the desired amount of compression of the positive electrode 308, and the thickness of the negative electrode 310.

[0107] Specifically, the depth of the cavity 326 may be selected to be greater than a lower threshold depth of the sum of the thickness of the carbon foam 306 after substantially full compression and the thickness of the positive electrode 308 after substantially full compression (to avoid overstress and crushing of the carbon foam 306, which may hinder electrolyte flow), and less than an upper threshold depth of the sum of the thickness of the carbon foam 306 and the thickness of the positive electrode 308 (to avoid zero compression of the positive electrode 308 and possible gaps, which may result in insufficient contact of H2 with the electrolyte). For example, in an example where the thickness of the carbon foam 306 is 6 mm, the thickness of the positive electrode 308 is 3.4 mm, the desired compression of the positive electrode 308 is 0.4 mm (so as to achieve a desired compression pressure of 0.01 MPa), and the thickness of the negative electrode 310 is 0.2 mm, the depth of the cavity 326 may be 9.2 mm (=3.4 mm+6 mm+0.2 mm-0.4 mm). As another example, the thickness of the carbon foam 306 can be between 2 mm and 10 mm, the thickness of the positive electrode 308 can be between 1 mm and 10 mm, the desired compression of the positive electrode 308 can be between 0 mm and 2.34 mm (so as to achieve a desired compression pressure of 0 MPa to 0.09 MPa), and the thickness of the negative electrode 310 can be between 0.2 mm and 1 mm, so that the depth of the cavity 326 can be between 0.86 mm and 21 mm.

[0108] In additional or alternative examples, the thickness of the positive electrode 308 can be 20% to 120% of the thickness of the carbon foam 306. In one example, the thickness of the positive electrode 308 can be 100% to 110% of the thickness of the carbon foam 306. In one example, the depth of the cavity 326 can further depend on the crush strength of the carbon foam 306 (e.g., the depth of the cavity 326 can increase as the crush strength decreases). For example, when the depth of the cavity 326 is 9.2 mm (e.g., when the expected compression of the positive electrode is 0.4 mm), the foam crush safety factor (FOS) can be 5.78. In some examples, the foam crush FOS can have a minimum value of 0.34, where a foam crush FOS value of less than 1 can indicate that at least some crushing is expected. In some examples, the crush strength (in one example, 0.08 MPa to 0.03 MPa) of the carbon foam 306 may be reduced by heat treating the carbon foam 306 during its manufacture.

[0109] It should be understood that the electrode assembly 302 can be configured such that the depth of the cavity 326 is as small as possible (e.g., within the constraints described above) because a generally thinner electrode assembly 302 can result in a reduced overall size of the rebalanced cell and reduced resistance across the electrode assembly 302 (e.g., because the electrolyte flow can be closer to the negative electrode 310).

[0110] In this way, the electrode assembly 302 may include a sequentially stacked carbon foam 306 and an interface connection pair of a positive electrode 308 and a negative electrode 310, the positive electrode and the negative electrode being in coplanar contact with each other and being continuously conductive. Specifically, a first interface may be formed between the positive electrode 308 and the carbon foam 306, and a second interface may be formed between the positive electrode 308 and the negative electrode 310, the second interface being opposite to the first interface across the positive electrode 308, and each of the carbon foam 306, the positive electrode 308, and the negative electrode 310 may be conductive. Therefore, the electrode assembly 302 may be internally short-circuited so that the current flowing through the electrode assembly 302 may not be guided through an external load.

[0111] In an exemplary embodiment, and as discussed above, forced convection can induce H2 to flow into the electrode assembly 302 and across the negative electrode 310 (e.g., through a flow field plate interfacing with the negative electrode 310). Here, H2 can react with the catalytic surface of the negative electrode 310 via equation (4a) (e.g., the reverse reaction of equation (1)):

[0112] 1 / 2H2→H + +e - (Anode half reaction) (4a)

[0113] Proton (H +) and electron (e - ) can be conducted across the negative electrode 310 and into the positive electrode 308. The electrolyte guided through the electrode assembly 302 through the carbon foam 306 can be wicked into the positive electrode 308. At and near the second interface between the positive electrode 308 and the negative electrode 310, the Fe in the electrolyte 3+ It can be restored by equation (4b):

[0114] Fe 3+ +e - →Fe 2+ (Cathode half reaction) (4b)

[0115] Summarizing equations (4a) and (4b), the electrolyte rebalance reaction can be written as equation (4):

[0116] Fe 3+ +1 / 2H2→Fe 2+ +H + (Electrolyte Rebalance) (4)

[0117] Since the electrode assembly 302 is internally shorted, the cell potential of the electrode assembly 302 can be driven to zero as shown below:

[0118] 0=(E pos –E neg )–(η act +η mt +η ohm ) (7)

[0119] Where E pos is the potential of the positive electrode 308, E neg is the potential of the negative electrode 310, η act is the activation overpotential, η mt is the mass transfer overpotential, and η ohm is the ohmic overpotential. Figure 3 For an electrode assembly 302 configured as in mt and η act can be ignored. Further, η ohm can depend on the overpotential η of the electrolyte 电解质 and the overpotential η of the carbon felt forming the positive electrode 308 毡 , as shown below:

[0120] η ohm =η 电解质 +η 毡 (8)

[0121] Thus, the performance of the electrode assembly 302 may be affected at least by the resistivity σ of the electrolyte. 电解质and the resistivity σ of carbon felt 毡 The conductivity of the electrolyte and the conductivity of the carbon felt can be further determined by the resistance of the electrolyte, R 电解质 and the resistance R of the carbon felt 毡 , which can be given as:

[0122] R 电解质 =σ 电解质 ×t 电解质 / A 电解质 (9)

[0123] R 毡 =σ 毡 ×t 毡 / A 毡 (10)

[0124] where t 电解质 is the thickness of the electrolyte (e.g., the height of the electrolyte front), t 毡 is the thickness of the carbon felt (eg, the thickness of the positive electrode 308), A 电解质 is the effective area of ​​the electrolyte (front), A 毡 Thus, the performance of electrode assembly 302 may be further limited based on the front position of the electrolyte within the carbon felt and thus the distribution of electrolyte across carbon foam 306 and the amount of electrolyte wicked into the carbon felt forming positive electrode 308 .

[0125] In determining R 电解质 and R 毡 Afterwards, the current I of the electrode assembly 302 组合件 It can be determined as:

[0126] I 组合件 =(E pos –E neg ) / (R 电解质 +R 毡 ) (11)

[0127] And the rate of the electrolyte rebalance reaction v 再平衡 (For example, Fe 3+ The reduction rate of ) can be further determined as:

[0128] v 再平衡 =I 组合件 / (nFA 再平衡 ) (12)

[0129] Where n is the number of electrons flowing through the negative electrode 310, F is the Faraday constant, and A 再平衡 is the effective area for the electrolyte rebalance reaction (e.g., the area of ​​the interface between the electrolyte front and the negative electrode 310). As a use case example, for a毡 = 3mm uncompressed carbon felt, v 再平衡 It may have a maximum value of 113 mol / m2-hr. However, in alternative examples, other properties of the uncompressed carbon felt may be used.

[0130] Hydrogen flows through the rebalance cell 202, such as Figure 2A and 2B As shown, it can be realized by at least two modes. The first flow mode is Figure 4A and 4B It is shown in Figure 2B The hydrogen outlet port 212 is shown open. In contrast, the second flow mode is Figure 5A and 5B It is shown in Figure 2B The hydrogen outlet port 212 is shown as being closed. Closing the hydrogen outlet port provides a dead-end flow configuration. Figures 4A-5B The cutting plane of the cross-sectional view is parallel to the zx plane and extends through the central axis of the hydrogen inlet port 210 .

[0131] Now specific reference Figure 4A and 4B , respectively, show a cross-sectional view and an enlarged inset 450 of the rebalanced cell 202. Each of the cross-sectional view and the enlarged inset 450 depicts exemplary aspects of H2 flow within the rebalanced cell 202. Specifically, the enlarged inset 450 enlarges a portion of the cross-sectional view defined by the dashed oval 410.

[0132] like Figure 4A and 4B As shown, the rebalanced cell 202 may include an electrode assembly stack 402 formed as a stack of individual electrode assemblies 302, the individual electrode assemblies being aligned such that the hydrogen inlet channel segments 318a of each electrode assembly 302 form a continuous hydrogen inlet channel 404 with the hydrogen inlet channel segments 318a of each electrode assembly 302. A hydrogen inlet manifold 406 may be further included in the hydrogen inlet channel 404, the hydrogen inlet manifold 406 fluidly coupling the hydrogen inlet channel 404 to the hydrogen inlet port 210.

[0133] The corresponding hydrogen inlet channel O-ring 322a and the outer O-ring 324 can seal the hydrogen inlet channel 404 at the interface between the paired electrode assemblies 302. It should be understood that the cut portion of the rebalanced battery cell 202 is Figure 4A Cross-sectional view and Figure 4B 450, and rebalancing the battery cells 202 (e.g., Figure 2A and 2BFurther, it should be understood that more or fewer electrode assemblies 302 may be included in the electrode assembly stack 402 than shown in the cross-sectional view for a given application (however, in one use case example, scaled-up performance may be substantially insensitive to H2 flows with H2 utilization equal to or less than 50%). Further, although reference is made to Figure 4A and 4B The structural features of the hydrogen inlet channel 404 and adjacent components are described in detail, but it should be understood that the corresponding hydrogen outlet channel (e.g., by aligning the hydrogen outlet channel segment 318b of each electrode assembly 302 (see Figure 3 ) and structural features of adjacent components may be similarly configured (except that a hydrogen outlet manifold in fluid communication with the hydrogen outlet passages may be positioned opposite the hydrogen inlet manifold 406 along the x and z axes).

[0134] As shown, and as indicated by arrow 408a, H2 enters the hydrogen inlet port 210. H2 can be delivered from a hydrogen source such as a hydrogen flow generator or a hydrogen storage tank. Next, as indicated by arrow 408b, hydrogen flows from the hydrogen inlet port 210 to the hydrogen inlet manifold 406. Next, as indicated by arrow 408c, hydrogen flows from the hydrogen inlet manifold 406 through the hydrogen inlet passage 404. The gas flows from the hydrogen inlet passage 404 to the hydrogen inlet passage 452 between the electrodes, as indicated by arrow 408d.

[0135] exist Figure 4A and 4B In the electrode assembly stack flow configuration shown, Figure 2B The hydrogen outlet port 212 is shown open. Thus, hydrogen flows across the electrode assembly stack 402 (generally in a direction parallel to the x-axis) through the hydrogen channels 420 between the plates 304 and the negative electrode 310, as indicated by arrow 408e. Arrow 408f depicts hydrogen flowing from the hydrogen channels 420 to the hydrogen outlet manifold and then to the Figure 2B Flow of hydrogen gas through the outlet port 212 is shown. In this way, hydrogen gas can flow efficiently through the battery cell.

[0136] Reference now Figure 5A and 5B , respectively, show a cross-sectional view and an enlarged inset 450 of the rebalanced cell 202. Each of the cross-sectional view and the enlarged inset 550 depicts exemplary aspects of H2 flow within the rebalanced cell 202. Specifically, the enlarged inset 550 enlarges a portion of the cross-sectional view defined by the dashed oval 510.

[0137] exist Figure 5A and 5B In the rebalanced cell flow configuration shown, Figure 2B The hydrogen outlet port 212 is shown closed, thereby providing a dead end for the hydrogen flow, as mentioned above.

[0138] The electrode assembly stack 402 in the rebalancing battery cell 202 is again Figure 5A and 5B , wherein the electrode assemblies 302 are arranged in sequence. In the illustrated example, each electrode assembly 302 also includes a negative electrode 310, a positive electrode 308, an activated carbon foam 306, a plate 304, and a hydrogen inlet channel sealing insert 320a. However, in other examples, other electrode assembly configurations may be used.

[0139] As shown, and as indicated by arrow 508a, H2 enters the hydrogen inlet port 210. Next, as indicated by arrow 508b, hydrogen flows from the hydrogen inlet port 210 to the hydrogen inlet manifold 406. Next, as indicated by arrow 508c, hydrogen flows from the hydrogen inlet manifold 406 through the hydrogen inlet passage 404. Hydrogen flows from the hydrogen inlet passage 404 to the hydrogen inlet passage 452 between the electrodes, as indicated by arrow 508d. This initial stage of hydrogen flow is similar to Figure 4A and 4B The initial part of the hydrogen flow pattern depicted in .

[0140] However, if Figure 5A and 5B As shown, as indicated by arrow 508e, hydrogen flows from hydrogen channel 420 and through negative electrode 310, and then through positive electrode 308. In this way, since the hydrogen outlet is closed, the hydrogen is forced to pass through the electrolyte side of the electrode assembly. Once the hydrogen is on the positive side of the electrode assembly, the gas flows into the electrolyte outlet manifold and then through the electrolyte outlet manifold. Figure 2A The hydrogen gas is shown exiting from the release port 214. To elaborate, the hydrogen gas flows into the page and toward Figure 2A The hydrogen release port 214 is shown. Further, some hydrogen flow can be entrained in the electrolyte and discharged from Figure 2A The electrolyte exits from port 208 as shown.

[0141] Figures 4A-5B The two flow modes in the rebalanced cell 202 depicted in FIG. 1 allow four different series pipe directions to connect multiple rebalanced cells, thereby increasing (e.g., maximizing) the hydrogen flow rate through each rebalanced cell. Thus, the cells can achieve the desired reaction rate, thereby improving the battery efficiency. Figure 6-9 Describes the use of Figure 1Different flow arrangements in a rebalancing cell system 600 for a redox flow battery, such as the redox flow battery 11 or other suitable redox flow battery, are shown.

[0142] exist Figure 6-9 In each of the figures, the rebalanced battery cell system 600 includes similar components, including a first rebalanced battery cell 602 and a second rebalanced battery cell 604. These rebalanced battery cells may include a stack of electrode assemblies with similar structures to improve manufacturing efficiency. The rebalanced battery cell system 600 further includes a hydrogen source 606, which includes a hydrogen storage tank 608 and a hydrogen flow generator 610 (e.g., a venturi injector or a hydrogen injector), which can be used with a hydrogen gas generator such as a venturi injector or a hydrogen gas injector. Figure 1 The venturi injector may include a constriction that introduces hydrogen into the gas flow at the restriction.

[0143] Rebalancing cells 602 and 604 can be done with Figure 2A and 2B The rebalanced cells 202 shown share at least some functional and structural features. Specifically, the first rebalanced cell 602 includes a hydrogen inlet port 612, a hydrogen outlet port 614, and a hydrogen release port 616. The second rebalanced cell 604 also includes a hydrogen inlet port 618, a hydrogen outlet port 620, and a hydrogen release port 622. The first rebalanced cell 602 and the second rebalanced cell 604 may further include a positive electrode side inlet and outlet through which the electrolyte flows.

[0144] The hydrogen storage tank 608 includes an inlet 624 and an outlet 626. The flow generator 610 similarly includes an inlet 628 and an outlet 630. Figure 6-9 Depicted are different flow arrangements 650, 750, 850, and 950 of the components of the rebalanced cell system 600. To achieve the variations in flow arrangements, different ports in the first and second rebalanced cells are fluidly connected by conduits, tubing, etc. through different schemes.

[0145] Figure 6The flow configuration 650 shown is a positive pressure setting relative to a hydrogen storage tank using a hydrogen side (negative side) inlet port and an outlet port. In this flow configuration, the high pressure side (outlet 630) of the hydrogen flow generator 610 is fluidly connected to the hydrogen inlet port 612 in the first rebalanced cell 602. Further, the hydrogen outlet port 614 in the first rebalanced cell 602 is fluidly connected to the hydrogen inlet port 618 in the second rebalanced cell 604. Still further, the hydrogen outlet port 620 in the second rebalanced cell 604 is in fluid communication with the inlet 624 of the hydrogen storage tank 608, and the outlet 626 of the hydrogen storage tank is fluidly connected to the inlet 628 of the hydrogen flow generator 610.

[0146] Figure 7 The flow configuration 750 shown is a positive pressure setting relative to the hydrogen storage tank 608 using the hydrogen inlet port 612 and the hydrogen release port 616 of the first rebalanced cell 602. Specifically, in the flow configuration 750, the high pressure side (outlet 630) of the hydrogen flow generator 610 is fluidly connected to the hydrogen inlet port 612 of the first rebalanced cell 602. Then, the high pressure hydrogen enters the hydrogen channel (negative channel) and is forced into the electrolyte section (positive side) by closing the hydrogen outlet. Then, the hydrogen release port 616 of the first rebalanced cell 602 is fluidly connected to the hydrogen inlet port 618 of the second rebalanced cell 604. Next, the hydrogen release port 622 of the second rebalanced cell 604 is fluidly connected to the inlet 624 of the hydrogen storage tank 608.

[0147] Figure 8 The flow configuration 850 shown is Figure 6 and 7 The combination of flow configurations 650 and 750 is shown. To elaborate, the hydrogen release port 616 and the hydrogen outlet port 614 of the first rebalanced cell 602 are connected to the hydrogen inlet port 618 of the second rebalanced cell 604. Further, the hydrogen release port 622 and the hydrogen outlet port 620 of the second rebalanced cell 604 are connected to the hydrogen storage tank 608.

[0148] Fig. 9The flow configuration 950 shown is a negative pressure setting relative to the hydrogen storage tank 608. In this flow configuration, the low pressure side (inlet 628) of the hydrogen flow generator 610 is connected to the hydrogen release port 622 of the second rebalanced cell 604. Further, the hydrogen release port 618 in the first rebalanced cell 602 is connected to the hydrogen inlet port 618 in the second rebalanced cell 604. Still further, in this flow configuration, the hydrogen inlet port 612 in the first rebalanced cell is connected to the outlet 626 of the hydrogen storage tank 608, and the outlet 630 of the flow generator 610 is fluidly connected to the inlet 624 of the hydrogen storage tank 608. When the flow generator 610 is turned on, a negative pressure is generated at the hydrogen release port 622 of the second rebalanced cell 604. This creates a pressure differential between the hydrogen inlet port 618 of the second rebalance cell 604 and the hydrogen release port 616 of the first rebalance cell 602, thereby causing hydrogen to flow from the higher pressure tank 608 through the lower pressure series-connected rebalance cells.

[0149] Although Figure 6-9 Two rebalancing cells are depicted, but additional rebalancing cells can be connected in series to the other cells as needed. When additional cells are added to the system, the last cell in the series can direct unused hydrogen back to the hydrogen storage tank or flow generator through the hydrogen outlet port. Thus, the number of cells in the system can be adjusted based on the design requirements of the end use.

[0150] Reference now Fig.10 , a method 1000 for operating a rebalanced battery cell system is shown. Specifically, the rebalanced battery cell system can be implemented in a redox flow battery to increase the H2 flow rate through the battery cells arranged in series, reduce excess H2, and rebalance the charge imbalance in the electrolyte therein. In an exemplary embodiment, the redox flow battery can be Figure 1 The redox flow battery 11, and the rebalancing battery cell system can be Figure 6-9 One or more rebalancing battery cell systems are shown, and the one or more rebalancing battery cell systems may include a plurality of rebalancing battery cells arranged in series, such as Figure 2A and 2B The method 1000 can therefore refer to Figure 1-9 The embodiments of the present invention may be considered individually or in combination (although it will be appreciated that similar methods may be applied to other systems without departing from the scope of the present disclosure). For example, using method 1000, at least some steps or portions of the steps (e.g., involving distribution H2) may be performed by Figure 1The instructions are executed by the controller 88 and may be stored as executable instructions in a non-transitory storage medium (e.g., a memory) that is communicatively coupled to the controller 88. To elaborate, the H2 flow may be driven by sending instructions from the controller to the hydrogen flow generator. Fig.10 Additional components described may be Figure 1-9 The corresponding component instance.

[0151] At 1002, the method includes receiving H2 from a hydrogen source at a first rebalanced cell through a hydrogen inlet port. As previously discussed, the hydrogen source may include a hydrogen storage tank and a hydrogen flow generator. Thus, in one example, the hydrogen flow generator may flow hydrogen directly to the inlet port of the first rebalanced cell through a conduit, a pipe, or the like. In other examples, hydrogen may flow directly from a storage tank through a conduit, a pipe, or the like to the inlet port of the first rebalanced cell.

[0152] Next at 1004, the method includes distributing hydrogen gas through the electrode assembly stack in the first rebalanced cell. The hydrogen flow pattern in the first cell may be Figure 4A and 4B Or the flow paths described in 5A and 5B.

[0153] At 1006, the method includes exhausting hydrogen from the first rebalanced cell and directing the hydrogen to a second hydrogen inlet port in the second rebalanced cell. Step 1006 may include sub-steps 1010 and / or 1012. At sub-step 1010, the method includes exhausting hydrogen through a first hydrogen outlet port in the first rebalanced cell and directing the gas to a second hydrogen inlet port. At sub-step 1012, the method includes exhausting hydrogen from the electrolyte through a first hydrogen release port in the first rebalanced cell and directing the hydrogen to a second hydrogen inlet port. In either sub-step 1010 and 1012, a port in the first rebalanced cell may be fluidly coupled to a port in the second rebalanced cell using a conduit, a pipe, or the like.

[0154] At 1014, the method includes distributing H2 throughout the electrode assembly stack in the second rebalanced cell. The hydrogen flow pattern in the second cell may be Figure 4A and 4B Or the flow paths described in 5A and 5B.

[0155] At 1016, the method includes discharging hydrogen from the second rebalanced battery cell and directing the hydrogen to a hydrogen source. Step 1016 may include sub-steps 1018 and / or 1020. At sub-step 1018, the method includes discharging hydrogen through a second hydrogen outlet port and directing the hydrogen to a hydrogen tank or a hydrogen flow generator. At sub-step 1020, the method includes discharging hydrogen from the electrolyte through a second hydrogen release port and directing the hydrogen to a hydrogen tank or a hydrogen flow generator. Next, at 1022, the method includes causing hydrogen to flow between a hydrogen storage tank and a hydrogen flow generator, or vice versa. For example, hydrogen can flow between the outlet of a hydrogen storage tank and the inlet of a flow generator. Method 1000 allows hydrogen to be effectively distributed between the rebalanced battery cells in series, thereby increasing the hydrogen flow rate and providing a more balanced hydrogen distribution in the battery cells.

[0156] The technical effect of the method described herein for rebalancing a battery cell system is to increase the hydrogen flow rate through the rebalanced battery cells, thereby improving battery efficiency and reducing hydrogen maldistribution between battery cells, compared to a parallel battery architecture.

[0157] The present invention will be further described in the following paragraphs. On the one hand, a rebalanced battery cell system for a redox flow battery is provided, the rebalanced battery cell system comprising a first rebalanced battery cell, the first rebalanced battery cell being fluidly connected in series with a second rebalanced battery cell and a hydrogen source; wherein the first rebalanced battery cell comprises a first electrode stack, the first electrode stack having a hydrogen gas flow path extending therethrough, and the pressure is higher than the pressure of the electrolyte in the first electrode stack; and wherein the second rebalanced battery cell comprises a second electrode stack, the second electrode stack having a hydrogen gas flow path extending therethrough, and the pressure is higher than the pressure of the electrolyte in the second electrode stack.

[0158] In another aspect, a method for a redox flow battery system is provided, the method comprising flowing hydrogen from a hydrogen source into a first hydrogen inlet port in a first rebalanced cell; and flowing hydrogen from a first hydrogen outlet port or a first hydrogen release port to a second negative hydrogen inlet port. In one example, the method may further comprise flowing hydrogen in series between the hydrogen storage tank and the hydrogen flow generator. In another example, the method may further comprise flowing hydrogen from one of a second hydrogen outlet port and a second hydrogen release port to the hydrogen source.

[0159] On the other hand, a rebalancing cell system for a redox flow battery is provided, the rebalancing cell system comprising a first rebalancing cell, the rebalancing cell comprising: a first hydrogen inlet port, the first hydrogen inlet port being fluidically connected to a hydrogen flow generator and one of a hydrogen storage tank; and a first hydrogen outlet port and / or a first hydrogen release port; and a second rebalancing cell, the second rebalancing cell comprising: a second hydrogen inlet port, the second hydrogen inlet port being fluidically connected to one of the first hydrogen outlet port and the first hydrogen release port; and a second hydrogen outlet port and / or a second hydrogen release port, the second hydrogen outlet port and / or the second hydrogen release port being fluidly connected to the hydrogen flow generator and one of the hydrogen storage tanks.

[0160] In any aspect or combination of aspects, the first rebalanced cell may include: a first hydrogen inlet port, the first hydrogen inlet port being fluidly connected to the hydrogen source; and a first hydrogen outlet port and / or a first hydrogen release port; and the second rebalanced cell may include: a second hydrogen inlet port, the second hydrogen inlet port being fluidly connected to one of the first hydrogen outlet port and the first hydrogen release port; and a second hydrogen outlet port and / or a second hydrogen release port, the second hydrogen outlet port and / or the second hydrogen release port being fluidly connected to the hydrogen source.

[0161] In any aspect or combination of aspects, the second hydrogen inlet port is in fluid communication with the first hydrogen outlet port.

[0162] In any aspect or combination of aspects, the first hydrogen release port is in fluid communication with the second hydrogen inlet port.

[0163] In any aspect or combination of aspects, the first hydrogen release port and the first hydrogen outlet port are both in fluid communication with the second hydrogen inlet port.

[0164] In any aspect or combination of aspects, the hydrogen source may include a hydrogen tank fluidly coupled in series to a hydrogen flow generator.

[0165] In any aspect or combination of aspects, the hydrogen flow generator may be in fluid communication with the first hydrogen inlet port.

[0166] In any aspect or combination of aspects, the hydrogen flow generator can be in fluid communication with the second hydrogen release port.

[0167] In any aspect or combination of aspects, the hydrogen flow generator may be a venturi injector or a hydrogen injector.

[0168] In any aspect or combination of aspects, the hydrogen source may include a hydrogen flow generator.

[0169] In any aspect or combination of aspects, the hydrogen source may include a hydrogen storage tank.

[0170] In any aspect or combination of aspects, the outlet of the hydrogen flow generator may be in series fluid communication with the inlet of the hydrogen storage tank.

[0171] In any aspect or combination of aspects, the outlet of the hydrogen storage tank may be in series fluid communication with the inlet of the hydrogen flow generator.

[0172] In any aspect or combination of aspects, the hydrogen flow generator may be a venturi ejector.

[0173] In any aspect or combination of aspects, the hydrogen flow generator may be a hydrogen injector.

[0174] In any aspect or combination of aspects, the layouts of the first rebalancing battery unit and the second rebalancing battery unit may be the same.

[0175] In any aspect or combination of aspects, the first rebalanced cell and the second rebalanced cell may include stacks of electrode assemblies of the same layout.

[0176] Figure 1-9An example configuration with relative positioning of each component is shown. If shown as directly contacting each other or directly coupled, then at least in one example, such elements can be referred to as directly contacting or directly coupled respectively. Similarly, at least in one example, elements shown as continuous or adjacent to each other can be continuous or adjacent to each other respectively. As an example, components placed in coplanar contact with each other can be referred to as being in coplanar contact. As another example, in at least one example, elements spaced apart from each other and only having space between them without other components can be referred to as such. As another example, elements shown as above / below each other, at opposite sides or on the left / right side of each other can be referred to as such relative to each other. Further, as shown in the accompanying drawings, in at least one example, the topmost element or the point of the element can be referred to as the "top" of the component and the bottommost element or the point of the element can be referred to as the "bottom" of the component. As used herein, top / bottom, up / down, above / below can be relative to the vertical axis of the accompanying drawings and used to describe the positioning of the elements of the accompanying drawings relative to each other. Therefore, in one example, the element shown as above other elements is vertically positioned above the other elements. As yet another example, shapes of elements depicted within the drawings may be referred to as having those shapes (e.g., as being annular, straight, planar, curved, rounded, chamfered, angled, etc.). Further, in at least one example, elements shown as intersecting one another may be referred to as intersecting elements or intersecting one another. Still further, in one example, an element shown as being within another element or shown as being outside another element may be referred to as such. Figure 2A-5B They are drawn approximately to scale, but other sizes or relative sizes may be used.

[0177] The following claims specifically point out certain combinations and sub-combinations that are considered novel and non-obvious. These claims may refer to "an" element or "first" element or its equivalent. Such claims should be understood to include the incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or characteristics may be claimed by amending the present claims or by presenting new claims in this or a related application. Such claims are also considered to be included in the subject matter of the present disclosure, whether broader, narrower, equal, or different in scope than the original claims.

Claims

1. A rebalancing cell system for a redox flow battery, the rebalancing cell system comprising: a first rebalanced cell in series fluid communication with a second rebalanced cell and a source of hydrogen gas; wherein the first rebalanced cell includes a first electrode assembly stack having a hydrogen flow path extending therethrough and having a pressure higher than a pressure of an electrolyte in the first electrode assembly stack; and Wherein the second rebalanced cell includes a second electrode assembly stack having a hydrogen flow path extending therethrough and having a pressure higher than a pressure of an electrolyte in the second electrode assembly stack.

2. The rebalancing battery cell system according to claim 1, wherein: The first rebalancing battery unit comprises: a first hydrogen inlet port in fluid communication with the source of hydrogen; and a first hydrogen outlet port and / or a first hydrogen release port; and The second rebalancing battery unit comprises: a second hydrogen inlet port in fluid communication with one of the first hydrogen outlet port and the first hydrogen release port; and A second hydrogen outlet port and / or a second hydrogen release port, wherein the second hydrogen outlet port and / or the second hydrogen release port is in fluid communication with the hydrogen source. 3 . The rebalanced battery cell system of claim 2 , wherein the second hydrogen inlet port is in fluid communication with the first hydrogen outlet port. 4 . The rebalanced battery cell system of claim 2 , wherein the first hydrogen release port is in fluid communication with the second hydrogen inlet port. 5 . The rebalanced battery cell system of claim 2 , wherein the first hydrogen release port and the first hydrogen outlet port are both in fluid communication with the second hydrogen inlet port.

6. The rebalanced battery cell system of claim 2, wherein the hydrogen source comprises a hydrogen tank fluidly coupled in series to a hydrogen flow generator. 7 . The rebalanced battery cell system of claim 6 , wherein the hydrogen flow generator is in fluid communication with the first hydrogen inlet port.

8. The rebalanced battery cell system of claim 6, wherein the hydrogen flow generator is in fluid communication with the second hydrogen release port. 9 . The rebalanced battery cell system according to claim 6 , wherein the hydrogen flow generator is a venturi injector or a hydrogen injector.

10. A method for rebalancing a battery cell system, the method comprising: flowing hydrogen from a hydrogen source into a first hydrogen inlet port in a first rebalance cell; and Hydrogen is caused to flow from the first hydrogen outlet port or the first hydrogen release port of the first rebalanced cell to the second hydrogen inlet port of the second rebalanced cell.

11. The method of claim 10, wherein the hydrogen source comprises a hydrogen flow generator.

12. The method of claim 11, wherein the hydrogen source comprises a hydrogen storage tank.

13. The method of claim 12, further comprising flowing hydrogen in series between the hydrogen storage tank and the hydrogen flow generator.

14. The method of claim 10, further comprising flowing hydrogen gas from one of a second hydrogen outlet port and a second hydrogen release port to the hydrogen source.

15. A rebalancing cell system for a redox flow battery, the rebalancing cell system comprising: A first rebalancing battery unit, wherein the first rebalancing battery unit comprises: a first hydrogen inlet port in fluid communication with one of a hydrogen flow generator and a hydrogen storage tank; and a first hydrogen outlet port and / or a first hydrogen release port; and A second rebalancing battery unit, wherein the second rebalancing battery unit comprises: a second hydrogen inlet port in fluid communication with one of the first hydrogen outlet port and the first hydrogen release port; and A second hydrogen outlet port and / or a second hydrogen release port, wherein the second hydrogen outlet port and / or the second hydrogen release port is in fluid communication with one of the hydrogen flow generator and the hydrogen storage tank.

16. The rebalanced battery cell system of claim 15, wherein an outlet of the hydrogen flow generator is in series fluid communication with an inlet of the hydrogen storage tank.

17. The rebalanced battery cell system of claim 15, wherein an outlet of the hydrogen storage tank is in series fluid communication with an inlet of the hydrogen flow generator.

18. The rebalanced battery cell system of claim 15, wherein the hydrogen flow generator is a venturi injector.

19. The rebalanced battery cell system of claim 15, wherein the hydrogen flow generator is a hydrogen gas injector.

20. The rebalanced battery cell system of claim 15, wherein the first rebalanced battery cell and the second rebalanced battery cell include electrode assembly stacks of the same layout.

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