JP7108640B2 - An Alternative Low-Cost Electrode for Hybrid Flow Batteries - Google Patents

Description

(Cross reference to related application)
This application is an international application of US patent application Ser. U.S. Patent Application No. 15/601,560 is a continuation-in-part of U.S. Patent Application No. 14/984,416, entitled "Alternative Low-Cost Electrodes for Hybrid Flow Batteries," filed Dec. 30, 2015. is. US Patent Application No. 14/984,416 claims priority from US Provisional Patent Application No. 62/098,200, filed Dec. 30, 2014, entitled "Carbon-Coated Plastic Electrodes for Hybrid Flow Batteries." The entire contents of the above application are incorporated herein by reference for all purposes.

(Approval of Government Support)
This invention was made with Government support under Assignment No. DE-AR0000261 awarded by the DOE, ARPA-E Office. The Government has certain rights in this invention.

(field)
The present disclosure relates to hybrid flow battery systems and methods of assembling hybrid flow battery systems.

(Background technology and overview)
A reduction-oxidation (redox, redox) flow battery is an electrochemical storage device that stores energy in chemical form. The stored chemical energy is converted to electrical form by spontaneous reverse redox reactions. An electric current is applied to induce a reverse redox reaction to recover the distributed chemical energy. Hybrid flow batteries deposit one or more electroactive materials as solid layers on the electrodes. A hybrid flow battery contains chemicals that form a solid precipitated plating on the substrate at some point throughout the charge reaction, and this solid precipitated plating can also dissolve throughout the discharge reaction. During the charging reaction, chemicals can solidify on the surface of the substrate and form a plating near the electrode surface. Chemicals are typically metal compounds. In hybrid flow battery systems, the amount of metal plated during charging can limit the energy stored by a redox battery, and thus the energy stored by a redox battery is determined by the efficiency of the plating system and the volume and surface area that can be plated. can be

The positive and negative electrodes of redox flow batteries participate in electrochemical reactions for the storage and release of chemical energy. Electrodes are therefore considered to be an important component in batteries as they affect battery performance, capacity, efficiency and overall cost.

An example of a hybrid redox flow battery is an all-iron redox flow battery (IFB). IFB uses iron as the electrolyte for a reaction involving a negative electrode (also referred to herein as a plating electrode) where plating occurs and a positive electrode (also referred to herein as a redox electrode) where redox reactions occur. . The performance of IFB batteries can be classified into plating electrode performance (negative electrode), redox electrode performance (positive electrode), and ohmic resistance loss. On the plating electrode, ferrous (Fe ²⁺ ) ions gain electrons during charging, plate as solid iron on the substrate, and solid iron during discharging, as shown in equation (1) below. dissolves as a ferrous ion, releasing two electrons. The equilibrium potential for the iron plating reaction is -0.44V. On the redox electrode, redox reactions between ferrous and ferric (Fe ³⁺ ) ions occur during charging and discharging. At the positive electrode, two Fe ²⁺ ions lose two electrons to form Fe ³⁺ ions during charging, and two Fe ³⁺ ions lose two electrons during discharging, as shown in equation (2) below. of electrons to form Fe ²⁺ . The equilibrium potential between ferrous and ferric ions is +0.77V. Therefore, the reactions in IFB redox flow batteries are reversible.
Fe ²⁺ + 2e ⁻ ⇔ Fe ⁰ (negative electrode) (1)
2Fe ²⁺ ⇔ 2Fe ³⁺ + 2e ⁻ (positive electrode) (2)

At the IFB anode, the ferrous iron reduction reaction competes with two side reactions. In the reduction of the hydrogen protons H ⁺ (reaction (3)), two hydrogen protons each accept a single electron to form hydrogen gas H ₂ , and in the corrosion of the deposited metallic iron the ferrous ions Fe ²⁺ ( reaction (4)), respectively.

These two side reactions can reduce overall cell efficiency because electrons transferred to the negative electrode can be consumed by hydrogen production rather than iron plating. In addition, these side reactions can lead to electrolyte imbalance, which in turn can lead to loss of battery capacity over time.

The Fe ²⁺ /Fe ³⁺ redox reaction at the positive electrode is kinetically fast. Therefore, the performance of IFB cells can be limited by anode performance, which is a result of plating rate, plating resistance, and plating mass transport loss. Furthermore, the capacity of an IFB battery is determined by the amount of solid iron that the negative electrode can store. Also, the efficiency of an IFB cell is related to the extent of side reactions such as side reactions (3) and (4) on the plating electrode. Therefore, it is desirable to select plating electrodes with optimized properties for battery performance and efficiency at minimal cost.

Currently, a titanium (Ti)-based mesh material is used as a negative electrode (plating electrode), and a carbon (C)-based porous material such as carbon paper or carbon felt is used as a positive electrode. Both the negative and positive electrodes consist of an interdigitated electrolyte flow field (IDFF). The Ti material is stable in the negative half-cell environment and the mesh increases the total surface area and plating yield. Current electrode materials are stable during charging cycles where high potentials can be applied to the electrodes. However, these plating and redox electrode materials are expensive and add to the overall battery cost. The Ti material also exhibits a catalytic effect on the hydrogen evolution reaction. Therefore, the use of Ti materials can increase the extent of side reactions such as hydrogen proton reduction (3). Furthermore, existing non-Ti-based woven mesh electrodes can be too costly and provide insufficient plating density for desired battery charging capacity. Furthermore, operating redox flow battery systems at higher plating densities increases electrolyte flow and bubble generation rates, which cannot be practically accommodated by conventional flow battery electrode configurations. , which can weaken the electrode plating and degrade the electrode. In addition, conventional flow battery electrode configurations can have higher current density distribution variances, which can lead to premature short circuiting of redox flow battery systems.

The inventors have found that the above problems can be at least partially addressed by the following redox flow battery: a first electrode disposed on the first side of the membrane and the first side is a membrane interposed between second electrodes disposed on a second side of the opposing membrane; and a first flow field plate comprising a plurality of positive flow field ribs; Each of the flow field ribs contacts a first electrode at a first support region on the first side and the second electrode has an electrode spacer positioned between the membrane and the second flow field plate. wherein the electrode spacer includes a plurality of primary ribs, each of the plurality of primary ribs contacting the second flow field plate at a second support region on the second side, each of the second support regions comprising: A redox flow battery aligned opposite one of the plurality of first support regions.

In another embodiment, a method of assembling a redox flow battery includes sandwiching a plating electrolyte flow field and a plating electrode spacer between the membrane and a plating flow field plate on the plating side of the membrane, the plating electrode spacer comprising a plurality of main ribs. sandwiching a redox electrolyte flow field between a redox electrode and a redox flow field plate on the redox side of the membrane, the redox electrode including a plurality of positive flow field ribs, and each of the plurality of main ribs comprising a plurality of When the plating flow field plate and the redox flow field plate are compressed toward the membrane, the main ribs sandwich the membrane without substantially changing the dimensions of the plating electrolyte flow field. including oppositely supported by opposite positive flow field ribs.

In another embodiment, the redox flow battery comprises a negative electrode spacer interposed between the negative side of the membrane and the negative flow field plate and a positive electrode spacer interposed between the positive side of the membrane and the positive flow field plate. and wherein the negative electrode spacer includes a plurality of major ribs, the positive electrode includes a plurality of positive flow field ribs aligned opposite the across-the-membrane main ribs, and a negative flow field rib. The field plate includes a continuous flat plating surface facing the membrane and a non-interdigitated anode electrolyte flow field sandwiched between the plating surface and the membrane.

In this way, novel redox flow battery systems can be provided that include larger electrode gaps, which can lead to higher plating current densities and battery charge capacities, higher electrolyte flows and bubble Incidence can be accommodated. In addition, current density distribution spread, ohmic losses, battery short circuits, and manufacturing and operating costs can be reduced.

It should be understood that the above summary is provided to introduce in a simplified form a selection 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 following the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.

The patent or application file contains at least one drawing executed in color. Copies of patents or patent application publications with color drawings will be provided by the Patent and Trademark Office upon request and payment of the necessary fee.
FIG. 1 shows a schematic diagram of an exemplary redox flow battery system.
FIG. 2 shows the Fe plating rate on various electrodes.
FIG. 3A shows an electron micrograph of a carbon-coated plastic mesh electrode.
FIG. 3B shows an electron micrograph of a carbon-coated plastic mesh electrode.
FIG. 4 shows a negative electrode performance comparison between an uncoated plastic mesh, two coated plastic meshes, and a Ti mesh as a baseline.
FIG. 5 shows the negative electrode pressure between a hydrophobic uncoated mesh and the same mesh with a hydrophilic coating.
FIG. 6 shows an example of hydrogen bubbles trapped in an uncoated mesh and how it affects the position and morphology of the coated Fe.
FIG. 7 shows a schematic of the coating on the plastic mesh.
FIG. 8 shows an exemplary method for manufacturing a coated plastic mesh electrode.
FIG. 9 shows carbon-coated plastic mesh electrode performance.
FIG. 10 shows carbon-coated plastic mesh electrode performance over cycles.
FIG. 11 is a table showing distribution of current density distribution and battery short-circuit time.
12-13 are tables showing the distribution of current density distributions for various electrode configurations.
Figures 14-15 show current density distributions and cell validation data plots for the various electrode configurations of Figures 12-13.
FIG. 16 shows a plan view of an exemplary electrode configuration for a redox flow battery system.
17A shows an enlarged partial detail view of the example electrode configuration of FIG.
17B-17E show enlarged partial cross-sectional views of the example electrode configuration of FIG.
18A and 18B show exemplary plan and cross-sectional schematic views of an electrode configuration that includes an interdigitated flow field (IDFF).
FIG. 19 is a flow chart showing an example of a redox flow battery assembly method.
20A-20B show partial cross-sectional views of exemplary redox flow battery configurations with supported and unsupported electrode stack assemblies, respectively.
21A-21C show partial cross-sectional views of electrode stack assemblies including various primary rib configurations.
Figures 23A-23K show enlarged plan views of the various electrode configurations of Figures 12-13.
FIG. 24A shows an exploded plan view of an alternative representation of the electrode configuration.
FIG. 24B shows a top view of an electrode spacer included in the electrode configuration of FIG. 24A.
24C and 24D are cross-sectional views showing the electrode configuration of FIG. 24A along BB and AA sections, respectively.
FIG. 24E shows a detailed view of region C of the electrode configuration of FIG. 24A.
FIG. 24F shows a top view of the electrode configuration of FIG. 24A.
FIG. 25A shows a top view of another alternative representation of the electrode configuration.
25B and 25D are cross-sectional views showing the electrode configuration of FIG. 25A along AA cross section and CC cross section, respectively.
25C shows a detailed view of the electrode configuration of FIG. 25A in region B. FIG.

(detailed explanation)
The present disclosure relates to materials and methods for novel coated plastic mesh electrodes for use in redox flow battery systems that improve or maintain performance compared to current electrode materials while reducing overall cost. The example redox flow battery system shown in FIG. 1 can include an all-iron hybrid redox flow battery (IFB), a Zn—Br ²⁺ flow battery, or a Zn—NiOOH (MnO ₂ ) battery, and the disclosed redox flow battery system. In one example, for an IFB system, as shown in FIG. 2, it can be seen that the iron plating rate is initially slow on non-ferrous based substrates. Thus, as shown in FIGS. 3A and 3B, the disclosed coated plastic mesh electrodes improve or maintain performance after the first plating cycle. A comparison of the plating electrode performance between the baseline Ti mesh and the coated mesh is shown in FIG. The use of coated plastic mesh electrodes reduces the amount of electrode active material and thus the cost of expensive conductive materials. The negative pressure of the plastic mesh with the hydrophilic coating and the pressure of the plastic mesh without the coating are compared in the graph shown in FIG. Evidence of the negative plating properties of the uncoated plastic mesh is shown in FIG. The disclosed electrodes have optimized thickness and openings of the plastic mesh, as shown in FIG. 7, and a carbon coating, which reduces the electrode resistivity, as shown in FIGS. Improved performance compared to current redox flow electrodes.

As shown in FIG. 11, electrode configurations that exhibit higher current density distribution dispersion can accelerate battery cell short circuits. 12-13 compare various exemplary electrode configurations with associated current density distribution variances shown in FIG. 14 and the battery validation test data shown in FIG. Magnified views of the various electrode configurations of FIGS. 12-13 are shown in FIGS. 23A-23K. FIGS. 16 and 17A-17E show various views of exemplary electrode configurations having lower current density distribution variances, and FIG. 19 shows a redox flow diagram including the electrode configuration of FIGS. 16 and 17A-17E. A battery assembly method will be described. Figures 18A and 18B show an example electrode configuration for a redox flow battery comprising an interdigitated flow field (IDFF). 20A and 20B show example electrode configurations for redox flow batteries with supported and unsupported electrode stack assemblies. Two alternative representations of electrode configurations are shown in FIGS. 24A-24F and 25A-25D, respectively.

Referring to FIG. 1, an exemplary schematic diagram of a redox flow battery system 10 is provided in which a single redox battery cell 18 is shown. A single redox battery cell typically includes a negative electrode compartment 20 , a positive electrode compartment 22 and a separator 24 . A separator 24 is arranged between the negative electrode chamber and the positive electrode chamber. In some examples, multiple redox battery cells 18 may be combined in series and/or parallel to produce higher voltage and/or current within the redox flow battery system.

Anode compartment 20 can include a negative electrode 26 and a first electrolyte solution, also called a negative electrolyte solution, that includes an electroactive material. Similarly, the cathode compartment 22 can contain a cathode 28 and a second electrolyte, also called a cathode electrolyte, comprising an electroactive material.

Separator 24 may comprise an electrically insulating, ionically conductive barrier. The separator functions to prevent bulk mixing of the first electrolyte solution in the anode compartment 20 and the second electrolyte solution in the cathode compartment 22 while allowing the conduction of certain ions therethrough. In one example, separator 24 can include an ion exchange membrane. In another example, separator 24 can include a microporous membrane.

The electrolyte can typically be stored in a tank outside the redox battery cell 18 . The electrolyte may be pumped through anode compartment 20 and cathode compartment 22 via pumps 30 and 32, respectively. In the example shown in FIG. 1, the first electrolyte is stored in a first electrolyte source 50 that further includes an external first electrolyte tank (not shown), and the second electrolyte is stored in an external second electrolyte tank (not shown). It is stored in a second electrolyte source 52 which further includes two electrolyte tanks (not shown).

During battery charging, current is applied to the negative battery terminal 40 and the positive battery terminal 42 . During charging, the positive electrode 28 oxidizes the positive electrolyte, losing one or more electrons, and the negative electrode 26 reduces the negative electrolyte, gaining one or more electrons.

During battery discharge, a reverse redox reaction to the charging reaction occurs at the electrodes. Therefore, during discharge, the positive electrode electrolyte is reduced at the positive electrode 28 and the negative electrode electrolyte is oxidized at the negative electrode 26 . In one example, the positive and negative electrodes may be carbon coated plastic mesh electrodes as described below.

Electrochemical redox reactions in the anode compartment 20 and the cathode compartment 22 maintain a potential difference across the redox flow battery system and are capable of inducing a current through the conductors while the reaction is sustained. The amount of energy stored by a redox flow battery system, the capacity, can be limited by the amount of electroactive material in the electrolyte for discharge. The amount of electroactive material is based on the total amount of electrolyte and the solubility of the electroactive material. Additionally, the amount of energy stored by a redox flow battery system can be limited by the amount of solid iron that the negative electrode can store.

During operation of the redox flow battery system, sensors and probes can be used to monitor and control the chemical properties of the electrolyte, such as its pH, concentration, state of charge, and the like. For example, the redox flow battery system can include sensors 60 and 62 that can be arranged to monitor the state of the electrolyte in first electrolyte source 50 and second electrolyte source 52, respectively. As another example, a redox flow battery system can include sensors 70 and 72 that can be positioned to monitor the condition of anode compartment 20 and cathode compartment 22, respectively.

The redox flow battery system may also include other sensors positioned at other locations throughout the redox flow battery system to monitor chemical and other properties of the electrolyte. For example, the redox flow battery system can include one or more sensors located within the external acid tank to reduce precipitate formation in the electrolyte by pumping the redox flow battery system through an external pump. Can supply acid. One or more sensors can monitor the amount of acid or pH in the external acid tank. Additional external tanks and sensors may be included to supply other additives to the redox flow battery system.

The redox flow battery system can be at least partially controlled by a control system including controller 80 . Controller 80 may receive sensor information from various sensors located within the redox flow battery system. For example, controller 80 may operate pumps 30 and 32 to control the flow of electrolyte through redox battery cell 18 . As such, controller 80 may be responsive to one or more sensors and/or probes located throughout the redox flow battery system.

A hybrid flow battery is a redox flow battery that can be characterized by the deposition of one or more electroactive materials as solid layers on the electrodes. In a hybrid flow battery system, the charge capacity of the redox battery can be limited by the amount of metal plated during battery charging, thus the charge capacity of the redox battery depends on the efficiency of the plating system and the availability of the plating. It can depend on the available amount and surface area available.

In hybrid flow battery systems, the negative electrode 26 is also called the plating electrode and the positive electrode 28 is also called the redox (oxidation-reduction) electrode. The anode electrolyte in the battery's anode compartment 20 (also referred to herein as the plating side) is referred to as the plating electrolyte, and the cathode electrolyte in the battery's cathode compartment 22 (also referred to herein as the redox side) is referred to as the redox electrolyte. It can be called an electrolyte.

As previously mentioned, one example of a hybrid flow battery is an IFB that uses iron as the electrolyte for the plating and redox reactions. The main components present in the IFB are similar to the hybrid flow battery shown in Figure 1, and the IFB contains a benign electrolyte containing iron salts. A safe electrolyte may have a near-neutral pH without being too acidic (pH<0) or alkaline (pH>14), for example, IFB anode electrolytes operate between pH 3-4. . Here, the term near-neutral pH provides a pH range in which the plastic mesh material used in the disclosed electrodes does not decompose in the electrolyte at the potentials applied during charging and discharging of the redox flow battery. IFB prevents mixing of a plating electrode where iron is deposited during charging and deplating during discharging, a redox electrode where oxidation-reduction reactions of ferrous ions and ferric ions occur, and an electrolytic solution. It contains a separator that provides a pathway and an electrolyte in which the energy of the IFB is stored. The capacity of an IFB battery can be determined not only by the amount of iron plated on the negative electrode, but also by the amount of electrolyte stored in the external tank.

The electrochemical redox reactions of IFB cells are summarized in equations (1) and (2), where the forward reactions (from left to right) represent the electrochemical reactions during battery charging and the reverse reactions (from right to Left) shows the electrochemical reaction during battery discharge.
Fe ²⁺ + 2e ⁻ ⇔ Fe ⁰ (negative electrode) (1)
2Fe ²⁺ ⇔ 2Fe ³⁺ + 2e ⁻ (positive electrode) (2)

On the plating side of the IFB, the plating electrolyte provides a sufficient amount of Fe ²⁺ such that during charging Fe ²⁺ gains two electrons from the negative electrode to form Fe ⁰ , which is plated onto the substrate. do. During discharge, the plated ^Fe0 loses two electrons, ionizes to Fe2 ⁺ , and dissolves again in the plating electrolyte. The equilibrium potential of the negative electrode reaction is −0.44 V, so reaction (1) provides the negative terminal for the IFB system. On the redox side of the IFB, the redox electrolyte provides Fe ²⁺ that loses electrons in the redox electrode during charging and oxidizes to Fe ³⁺ . During discharge, Fe ³⁺ gains electrons from the redox electrode to produce Fe ²⁺ . The equilibrium potential of the positive reaction is +0.77 V, so reaction (2) provides the positive terminal of the IFB system.

Therefore, the performance of an IFB system can depend on its plating electrode performance, redox electrode performance, and ohmic losses. On the positive electrode side of the IFB, an oxidation-reduction reaction between Fe ²⁺ and Fe ³⁺ shown in reaction (2) occurs during charging and discharging. Reaction (2) is kinetically fast with minimal side reactions and may not be a limiting factor in the performance of the IFB system.

On the negative side of the IFB, a plating reaction between Fe ²⁺ and Fe ⁰ occurs during charging and discharging, as shown in reaction (1). Ferrous ions Fe ²⁺ gain electrons and get plating as solid iron Fe ⁰ on the substrate. This plating reaction consists of two side reactions, the reduction of hydrogen protons H ⁺ (reaction (3)) where two hydrogen protons each accept one electron to form hydrogen gas H ₂ and ferrous ions Corrosion of deposited metallic iron to produce Fe ²⁺ (reaction (4)), respectively.

Both side reactions can reduce overall cell efficiency, as electrons transferred to the negative electrode may be consumed first by hydrogen production rather than iron plating. In addition, these side reactions can lead to an imbalance in the cathode electrolyte, resulting in loss of battery capacity over time. Moreover, the generated _H2 can be trapped at the negative electrode, which in turn reduces the electrochemically active area and significantly increases the electrode overvoltage.

Reaction (1) is kinetically slower than reaction (2) and may be a limiting factor in the performance of IFB systems. During charge and discharge cycles, the potential across the electrodes can be low when compared to other redox battery systems. It should be noted that the plating rate of other battery systems may be the limiting factor of battery performance.

Referring to FIG. 2, the plating rates of iron, Fe ⁰ and an exemplary IFB are shown for various electrode materials. When initially plating iron on non-ferrous based substrates such as non-Fe electrode 1 (206) and non-Fe electrode 2 (204), the iron plating rate is slow due to dissimilar materials. However, once a layer of iron is plated onto the substrate, the iron plating rate increases several orders of magnitude faster, as shown at the Fe electrode (202), as iron is plated onto the iron-coated substrate. do. The performance of IFB is mostly limited by the speed of the negative plating electrode which is a result of plating speed, resistance and mass transport losses. Therefore, as soon as iron is plated onto the substrate, the plating rate is significantly improved and is no longer the rate-limiting side, so various materials can be used as the negative plating electrode substrate. Therefore, electrodes used in redox flow batteries must retain or improve the plating rate and conductivity of electrodes such as Ti and C currently used in IFB systems. The disclosed coated plastic mesh electrodes maintain or improve performance as described below. The coated plastic mesh can survive in IFB operating conditions because the IFB electrolyte is in the range of pH 1-4, not too acidic or alkaline, and the electrode potential is low, thus carbon-coated plastic mesh electrode does not degrade during operation.

Referring to FIGS. 3A and 3B, electron micrographs of disclosed electrodes comprising carbon material coated plastic meshes for use in redox flow batteries are shown. Other exemplary coating materials can be metal oxides (such as _TiO2 ) and/or hydrophilic polymers (such as sulfonated PEEK and perfluorosulfonic acid (PFSA)).

Plastic meshes can be made from a variety of plastics. In one example, the plastic mesh material may be polypropylene (PP). In another example, the plastic mesh material may be polyolefin.

The coating material can be selected from any commercially available carbon ink. For example, the carbon material may be a carbon ink selected from Electrodag, C220, C120-24, and CM112-48. Figures 3A and 3B show electron micrographs of carbon-coated plastic mesh electrodes at different magnification levels. Examples of other coating materials include, but are not limited to, metal oxides (such as _TiO2 ) and hydrophilic polymers (such as sulfonated PEEK and perfluorosulfonic acid (PFSA)). These coating materials can change the base plastic material from hydrophobic to hydrophilic. Thus, the hydrophilic mesh can reduce the amount of hydrogen bubbles trapped within the plastic mesh.

In some embodiments, the plastic mesh may be a monopolar mesh. In other embodiments, the plastic mesh may be a bipolar mesh. In still other embodiments, the plastic mesh may be a woven mesh. In yet another embodiment, the plastic mesh may be a stretched mesh.

In some embodiments, the plastic mesh can be treated to improve adhesion of the carbon material to the plastic mesh. In one example, a solvent treatment is used to treat the plastic mesh to improve adhesion of the carbon material to the plastic mesh. In another example, a plasma treatment is used to treat the plastic mesh to improve adhesion of the carbon material to the plastic mesh. In other examples, mechanical abrasion, UV radiation or electron beam plasma can be used.

In other exemplary embodiments, the covering material of the plastic mesh may be electrically conductive and may include materials such as carbon. A carbon material can be applied to the plastic mesh to form a carbon coating. Carbon coatings are electrically conductive when used in redox flow battery systems. Carbon coatings can be applied using a variety of techniques. In one example, the carbon material may be coated by airbrushing. In another example, the carbon material may be coated by dip coating. In yet another example, the carbon material may be coated by roller coating.

In some examples, the coating material may further comprise a non-conductive material such as a metal oxide (eg, _TiO2 , etc.) or a hydrophilic plastic coating (eg, SPEEK, PFSA, etc.). In some embodiments, a non-conductive coating can be applied to make the plastic mesh more hydrophilic. Furthermore, by increasing the hydrophilicity, the hydrogen bubbles generated by side reactions 3 and 4 can be prevented from being trapped within the plastic mesh.

Carbon-coated plastic mesh electrodes exhibit uniform coverage of the carbon coating, as shown in FIGS. 3A and 3B. The use of plastic mesh reduces the amount of expensive conductive materials such as carbon fiber or titanium currently used in IFB systems, while reducing redox and plating reactions due to the large surface area and conductivity of the carbon coating. Maintains speed and allows high reserves of metal during plating. Carbon-coated plastic mesh electrodes can be used as plating electrodes and/or redox electrodes.

Referring to FIG. 4, this figure shows a graph showing the negative performance of plastic mesh electrodes compared to a Ti mesh baseline. An uncoated plastic mesh 408 and a plastic mesh with two types of carbon coating applied (402, 404) are shown compared against a Ti mesh baseline 406. FIG. The X-axis plot (CD) represents the current density, measured in mA/cm ² , and the Y-axis plot (V) represents the performance of the plating electrode on the achieved overvoltage. Plating electrode performance was measured with reference to an Ag/AgCl reference electrode inserted in a negative flow field. Initial voltage changes at low current densities can indicate plating rate overvoltages.

As shown in FIG. 4, the highest plating overvoltage results from the uncoated plastic mesh only configuration. This may be due to the reduced electrode surface area as the uncoated plastic mesh is non-conductive.

In one embodiment, two carbon ink coated plastic meshes (1 and 2 (shown as 402 and 404 in FIG. 4)) exhibit similar or even lower overvoltages relative to the Ti mesh baseline 406. . This may suggest that similar or greater conductive surface area is available on the coated plastic mesh relative to the surface area of the Ti baseline. At higher current densities, performance loss may be determined by ohmic resistance loss, which is the result of a combination of mesh resistance and electrolyte resistance within the mesh. Thus, ohmic resistance may be the result of a combination of electrolyte conductivity, mesh open area, mesh thickness, and mesh electrical resistance.

Referring now to FIG. 5, this figure compares the pressure in the anode chamber while operating with an uncoated hydrophobic plastic mesh and a coated conductive hydrophilic plastic mesh. As an example, pressure transducers were attached to the IFB cell to characterize the anode and cathode electrolyte pressures of the IFB during cycling. During initial charging, negative pressure may increase as indicated by the evolution of hydrogen. Under the same operating conditions, this pressure increase 504 was significantly higher with an uncoated hydrophobic plastic mesh than with the same mesh with a hydrophilic coating 502, as shown in FIG. Furthermore, with each cycle, the internal pressure of the uncoated plastic mesh increases, suggesting that the hydrogen bubbles may not be effectively purged out with each cycle. However, coating this mesh with a hydrophilic carbon coating reduced the mesh contact angle with DI water from >90° to less than 45°. Therefore, the same battery can be operated at a much lower and more repeatable pressure range, which may indicate that the evolving hydrogen was effectively purged out of the battery during cycling performance. . This purging of hydrogen gas can be important in the operation of the cell as it can reduce the cell's active area if it is not effectively purged out of the cell. Thus, while exhibiting substantially higher operating current densities, cell performance can degrade. In addition, it also has the potential to reduce battery plating amounts, which can be further illustrated by the photographs provided in FIG.

FIG. 6 shows a photograph of the above uncoated plated electrode when the battery is fully charged. The illustrated transparent mesh structure 602 illustrates the uncoated plastic mesh of one embodiment. The dark surface under the mesh is plated iron 606 plated onto the plastic mesh. The non-uniform bubble-like structure 604 marked in the figure indicates deformation of the plated iron 606 left by hydrogen bubbles trapped during charging of the battery. Furthermore, this figure not only shows that the hydrogen bubbles have been trapped within the mesh, but also shows that iron plating 606 has developed around the hydrogen bubbles 604 . This inconsistent plating is caused, first of all, by the trapped hydrogen bubbles reducing the overall amount available for plating, the bubbles substantially reducing the active area on the plating electrode, which leads to uneven plating. and local overplating can result in local short circuits, which can be problematic for negative electrodes.

Referring to FIG. 7, a schematic illustration of applying coated plastic mesh as a redox or plating electrode in IFB is shown. 702 refers to flow plate channels through which electrolyte enters and exits the IFB cell. 706 refers to redox or plating electrodes, which can be carbon paper or Ti mesh or coated plastic mesh material. 704 refers to a membrane separator that separates the positive and negative compartments. The ohmic resistance of the electrode is the combined ionic and electrical resistance 706, with the ionic resistance determined by the electrolyte resistivity, mesh open area and mesh thickness, and the electrical resistance determined by the coating type, thickness and mesh wire size. be done. The ohmic resistance of 706 is only the ionic resistance through the electrolyte if a non-conductive coating is used. The dimensions of the coated plastic mesh electrode can be optimized for performance within the redox flow battery. For example, Table 1 below shows the surface area (mm ² ), open area, open volume and mesh thickness (mm ).

Carbon-coated plastic mesh electrodes can be manufactured to provide dimensions similar to current metal electrodes. Carbon-coated plastic mesh electrodes allow further refinement to the dimensions shown in Table 1 to optimize performance. For example, a carbon-coated plastic mesh electrode for use as an electrode has an open volume of 10% to 70%, a thickness of between about 0.20 mm and about 0.50 mm, and an open area of 15% to 65%. be able to. As used in this disclosure, the term "about" includes additional ranges slightly above or below the value that do not change the physical or resulting properties of the material. Carbon-coated plastic mesh electrodes can be optimized for conductivity, plating area, and the like.

Referring to FIG. 8, an exemplary method for manufacturing coated plastic mesh electrodes is provided. The method can provide an electrode for use in an IFB redox flow battery, including manufacturing a plastic mesh, treating the plastic mesh, and coating the plastic mesh. The fabricated electrodes can be used as positive or negative electrodes in IFB redox flow batteries.

At step 802, the method can include obtaining a starting material. For example, plastic mesh and carbon materials can be obtained. In one example, the plastic mesh can be made from polypropylene. In another example, the plastic mesh can be made from polyolefin. The coating material may be conductive, such as carbon ink. For example, the carbon inks may be one or more of Electrodag, C220, CM120-24, and CM112-48. The coating material may further comprise non-conducting materials such as metal oxides or hydrophilic polymers. For example, the metal oxide may be _TiO2 and the hydrophilic polymer may be SPEEK or PFSA.

At step 804, the method can include obtaining a plastic mesh. The plastic mesh can include a thickness optimized for surface area, open area, open volume, and electrode performance. For example, a plastic mesh can be selected to include the dimensions shown in Table 1 above. The resulting plastic mesh may be made from polypropylene, polyolefin, etc. and may be monopolar, bipolar or woven.

At step 806 , the method can include processing the plastic mesh produced at step 804 . Treating the plastic mesh can be done to improve adhesion for the subsequent coating step 808 . In some embodiments, the method includes treating the manufactured plastic mesh to improve adhesion of the carbon coating. In other embodiments, the method may not include treating the manufactured plastic mesh to improve adhesion. In one example, treatment of the plastic mesh may be performed using solvent treatment. In another example, plasma treatment may be used to treat plastic mesh.

Various surface treatments that can be used to improve the adhesion of coatings to plastics include flame and corona, mechanical abrasion, solvent cleaning or swelling followed by wet chemical etching, or the application of special coatings in the form of chemical primers. including processing, or any combination thereof. Additional treatments such as ultraviolet (UV) irradiation, high energy density treatments such as electron beam and cold gas plasma methods, and combinations thereof can also be used. The methods described above are more widely accepted on a larger scale for substrate surface modification. These methods can provide mediators rich in reactive species such as energetic photons, electrons, free radicals, and ions, which then interact with the polymer surface to change its chemistry and/or morphology. can be made These processes can be readily used to modify the surface properties of plastic meshes.

At step 808, the method includes coating the plastic mesh with the selected material. In one example, coating the plastic mesh with the carbon material may be done by airbrushing. In another example, coating the plastic mesh with the carbon material may be done by dip coating. In yet another example, coating the plastic mesh with the carbon material may be done by roller coating. Coating thickness may be optimized for conductivity and/or plating. The coating may require heat treatment to cure and remove any solvent.

At step 810, the method can obtain a coated plastic electrode. Coated plastic electrodes can be used as plating electrodes and/or redox electrodes in redox flow battery systems. The method can then end.

Accordingly, electrodes can be manufactured for use in redox flow battery systems. Electrodes can be manufactured using the exemplary methods described above and are novel carbon-coated plastic mesh electrodes that improve battery performance and reduce cost. The use of low-cost plastic materials leads to novel carbon-coated plastic mesh-based electrodes for use in IFB systems, contrary to current thinking due to the instability of the plastics employed in current electrode systems. . Carbon-coated plastic mesh electrodes can be used at the negative and/or positive positions of the redox flow battery system.

Referring to FIG. 9, the performance of several carbon-coated plastic mesh electrodes is shown against a Ti mesh control electrode. In FIG. 9, the polarization plots of carbon-coated plastic mesh electrodes 904, 906, 908 provide improved or similar current density versus voltage response compared to Ti mesh control electrode 902. FIG. The uncoated plastic mesh electrode 912 exhibits a lower voltage response compared to the Ti mesh control electrode 902 and the carbon coated plastic mesh electrodes 904,906,908. The Electrodag electrode 910 exhibits good voltage at low current densities and lower voltage at high current densities compared to other carbon-coated mesh electrodes. This result shows that the carbon coating enhances the electrical conductivity of the carbon-coated plastic mesh electrode 912 compared to the uncoated plastic mesh electrode 912 . Carbon-coated plastic mesh electrodes therefore provide a low-cost alternative for use in redox flow batteries that enhances or maintains current density compared to currently used electrode materials.

Referring to FIG. 10, the cycling performance of the carbon-coated plastic mesh electrode is shown. A Ti mesh control electrode 1002 and a Ti vacuum electrode 1016 are included as a baseline. The carbon-coated plastic mesh electrode was cycled over 100 cycles and monitored for performance. 1, 24, 48, 72, 96 and 120 cycles of polarization of the carbon coated plastic mesh electrode are plotted at 1004, 1006, 1008, 1010, 1012 and 1014 respectively. From FIG. 10 it can be seen that the carbon-coated plastic mesh electrode retains its current density versus voltage response compared to the Ti vacuum electrode 1016 and exhibits an improved response compared to the Ti mesh control electrode 1002 .

Disadvantages of IDFF flow configurations and redox flow battery anode (eg, plated electrode) configurations with titanium mesh include high cost, poor plating density, and trapped air bubbles. Insufficient plating density prevents the redox flow battery system from achieving a sufficiently high battery charge capacity. For example, an IDFF flow configuration and a negative electrode configuration with Ti mesh are desirable for redox flow battery applications to maintain cost and battery performance metrics (such as reduced losses during charge-discharge cycling), but charging for more than 8 hours capacity cannot be provided. In addition, entrapment of air bubbles can reduce the available plating area of the electrode and can embrittle the plating electrode material, thereby reducing battery charge capacity and degrading the electrode.

ここで、Ｔ＝時間（ｓ）；Ｍ＝モル質量（ｇ／ｍｏｌ）；Ｊ＝電流密度（面積／ｃｍ^２）；ρ＝めっき金属の密度（ｇ／ｃｍ^３）；ｎ＝＃めっきされた金属１モル当たりの電子数；Ｆ＝ファラデー定数（９６４８５．３３６５ Ｃ／ｍｏｌ）。電流密度は、電極の活性領域Ａ（ｃｍ^２）に基づいて決定することができる。鉄レドックスフロー電池の場合、めっき金属は鉄であり、鉄めっき１モル当たりの電子数は２である。電池の充電量とめっき密度は、それぞれ式（６）、（７）に示すように計算される。

To reduce manufacturing costs, redox flow batteries can be designed to operate at higher current densities. For example, a redox flow battery system operating at a current density of 60 mA/cm ² can have one-fourth as many battery cells as a redox flow battery system operating at 15 mA/cm ² . However, redox flow batteries operating at higher current densities can present additional redox flow battery system design challenges. For example, plating stress can increase at higher plating current densities, resulting in higher stressed and more brittle plating electrodes. Additionally, redox flow battery systems with higher liquid electrolyte flow rates can be utilized to enable higher current densities to be delivered. Additionally, larger electrode gaps can be configured to accommodate higher flow rates. The electrode gap for a redox flow battery cell constitutes a representative length calculated from the ratio of current density to charge per metal ion plated on the electrode, as shown in equation (5).

where T = time (s); M = molar mass (g/mol); J = current density (area/cm ); ρ ⁼ density of plated metal (g/cm ³ ); Number of electrons per mole of metal; F = Faraday constant (96485.3365 C/mol). The current density can be determined based on the active area A (cm ² ) of the electrode. For iron redox flow batteries, the plating metal is iron and the number of electrons per mole of iron plating is 2. The battery charge and plating density are calculated as shown in equations (6) and (7), respectively.

In addition to accommodating the higher flow rates associated with providing higher current densities, the electrode gap of the redox flow battery can be further increased to reduce any gas evolution within the flow field of the anode electrolyte and at the surface of the anode. Sufficient purging can be allowed. For example, as described above with reference to equations (3) and (4), ^hydrogen gas can be generated. Removal of hydrogen gas reduces deterioration of the battery electrodes, as the presence of hydrogen in the negative electrode can reduce the electrode active area available for plating and can embrittle the plated metal there. Helpful. Performance metrics of redox flow battery systems can be affected by an increase in ohmic losses that can scale proportionally with current and electrode gap size. To accommodate higher current densities and allow sufficient gas purging, the electrode gap cannot be simply increased without limit.

16, 17A-17D, 20A, and 20B, these figures help reduce the dispersion of the current density distribution compared to conventional designs, while increasing the Structural features of the negative electrode configuration that scale to battery capacity, reduce manufacturing costs, maintain redox flow battery performance, and reduce bubble entrapment in the electrolyte flow field close to the surface of the electrode are shown. These configurations are three-dimensional xyz with the x-axis aligned with the width, the y-axis aligned with the length, and the z-axis aligned with the height or thickness of the electrode stack assembly. are shown corresponding to the coordinate axes. The z-axis refers to the horizontal axis perpendicular to the xy plane for each layer of the electrode stack assembly.

In a redox flow battery system, the negative electrode can be placed in an electrode stack assembly 2000 as shown in FIG. 20A. Electrode stack assembly 2000 may include an electrically insulating, ion-conducting barrier 2020, such as an ion exchange membrane, for example. A positive (redox) flow field plate 2010 and a positive electrode (redox electrode) can be placed on the positive (redox) side of the membrane. A positive electrode can be placed adjacent to the membrane to facilitate ion migration across the membrane to the negative side (plating side) of the stack assembly. This interposes the positive electrode between the positive flow field plate and the membrane and sandwiches the positive electrolyte flow field between the positive flow field plate and the positive electrode. The positive flow field plate 2010 may comprise a comb flow field plate including comb positive flow field plate ribs 2012 . In other examples, the positive flow field plate 2010 can include other configurations of ribbed flow field plates, such as a serpentine flow field plate with non-comb positive flow field plate ribs 2012 . An example of an interdigitated flow field (IDFF) plate 1800 is shown in FIG. 18 with interdigitated ribs 1812 and 1822 for directing electrolyte flow on the positive side of the membrane. In particular, electrolyte may be directed from inlet 1810 to outlet 1820 of positive flow field plate 2010 . As shown in cross-sectional view 1850 of a combed positive flow field plate, electrolyte flow (indicated by arrows 1830) from the combed inlet channels of combed ribs 1812 to the outlet channels of combed ribs 1822 flows through the porous positive electrode. 1840, thereby providing forced convection of the electrolyte. In other examples, the positive flow field plate may be a non-IDFF flow plate such as, for example, a serpentine flow plate, a spiral flow plate, a pin flow plate, or a parallel flow plate with non-comb ribs. Due to the dead-end channels, electrolyte fluid fills the comb-shaped dead-end channels before diffusing through the porous positive electrode 1840 from the inlet channel to the outlet channel to distribute the flow field more fully. The IDFF flow field can be advantageous because it allows

On the negative (plated) side of the electrode stack assembly (e.g., the negative side of membrane 2020), the anode electrolyte flow field is sandwiched between membrane 2020 and the anode configuration, which is metal during charging of the battery. plated flat negative flow field plate 2040 and non-conductive anode spacers 2026 (eg, plated electrode spacers). The negative electrode spacer 2020 is non-conductive and does not have a conductive coating, so no metal plating occurs during charging. However, the negative electrode spacers 2020 can facilitate plating to the negative flow field plate 2040 by making the distribution of electrolyte ions from the membrane 2020 to the negative flow field plate 2040 more uniform, resulting in a higher current density distribution. can reduce the variance of Anode spacers 2026 also help physically support the anode electrolyte flow field between membrane 2020 and negative flow field plate 2040, which sustains higher charging current densities and gas purge rates. In addition, it can help maintain a higher electrolyte flow rate. Since the negative flow field plate 2040 is flat, there is no defined negative electrolyte flow field. In this way, the electrode gap between the negative electrode and the negative flow field plate can be made larger compared to systems with non-flat negative flow field plates, resulting in a higher electrolyte flow rate associated with higher current densities. can correspond to the flow of Flat negative flow field plates also reduce the purging of gases such as hydrogen gas generated during charge and discharge chemical reactions (see equations (3) and (4)) compared to non-flat flow field plates. , thereby maintaining electrode active area for plating, reducing embrittlement of the plated metal, and increasing cell performance.

As shown in FIG. 20A, the anode structure includes an anode spacer 2026 located on the membrane facing side of the negative flow field plate 2040 . In other words, the anode spacer 2026 of the anode structure can be inserted between the membrane 2020 and the negative flow field plate 2040 . The negative electrode spacers 2026 are aligned parallel to the main ribs 2030 on the positive side of the membrane 2020 with a row of main ribs 2030 oriented parallel by the positive flow field plate ribs 2012 of the positive flow field plate on the positive side of the membrane 2020 . and rows of support ribs 2032 oriented more laterally and more laterally to the positive flow field plate ribs 2012 . As described above with reference to FIG. 18, the positive flow field plate ribs 2012 of the positive flow field plate 2010 may have interdigitated ribs. In other examples, however, the positive flow field plate 2010 can include non-interdigitated ribs, such as in parallel flow field plates or serpentine flow field plates.

In a negative electrode spacer 2026 in a negative configuration, each of the support ribs 2032 may be laterally connected to each of the main ribs 2030 . In some examples, the main ribs 2030 extend away from or distal to the support ribs 2032 and the membrane 2020 such that the support ribs 2032 are positioned proximate the membrane 2020 relative to the main ribs 2030. good too. The main rib 2030 is a solid monolithic structure with constant cross-section in the longitudinal direction (y-direction) parallel to the positive flow field plate ribs, as shown in the cross-sectional views of the electrode stack assembly in FIGS. 20A and 20B. may contain.

In addition to being oriented more parallel to the positive flow field plate ribs 2012 of the positive flow field plate 2010 , the main ribs 2030 are also oriented more parallel to the positive flow field plate ribs 2012 across the membrane 2020 . They may be aligned facing each other. Thus, when the negative flow field plate 2040 and the positive flow field plate 2010 are compressed toward the membrane 2020, the main ribs 2030 do not buckle, and the positive and negative electrolyte flow field shapes and Without changing dimensions, they are supported oppositely by opposite positive flow field plate ribs 2012 across the membrane. In other words, the primary ribs 2030 provide structural support for the positive flow field plate ribs 2012 and vice versa, thus compressing the electrode stack assembly 2000 during redox flow battery system assembly and operation. The flow and shape of the positive electrolyte flow field between the flow field plate 2010 and the positive electrode 2016 and the negative electrode electrolyte flow field between the negative flow field plate 2040 and the negative electrode 2026 spacers contract or change substantially. try not to The alignment of the main ribs 2030 opposite the positive flow field plate ribs 2012 of the positive support plate is such that the main ribs 2030 in the negative support area opposite the positive flow field plate ribs 2012 located within the positive support area. may include placing a The negative support area can correspond to the widthwise (eg, x-direction) dimension of the primary rib 2030 as indicated by the dashed line 2038 . The positive support area can correspond to the widthwise (eg, x-direction) dimension of the positive flow field plate ribs 2012 as indicated by the dashed line 2018 .

The position of the main ribs 2030 opposite the positive flow field plate ribs 2012 can include that the boundaries of the negative support area (eg, dashed line 2038) are within the boundaries of the positive support area (eg, dashed line 2018). can. If the boundary of the negative support area (eg, dashed line 2038) is wider than the boundary of the positive support area (eg, dashed line 2018), then the placement of the main ribs 2030 opposite the positive flow field plate ribs 2012 is the positive support area. is within the boundary of the negative support region (eg, dashed line 2038) (eg, dashed line 2018). Thus, the location of the main ribs 2030 opposite the positive flow field plate ribs 2012 is such that the positive support area is centered within the negative support area, or the negative support area is within the positive support area. centering the main rib 2030 across from the positive flow field plate rib 2012 so that it is centered on the . Additionally, if the main ribs are arranged parallel to the positive flow field ribs, each of the negative support areas will be aligned with the positive support areas when arranging the main ribs 2030 opposite the positive flow field plate ribs 2012. They may be arranged in parallel. In this way, the electrode stack assembly can support sufficient physical compression so that the positive electrodes on the positive and negative flow field plates during operation and assembly of the redox flow battery system. and the flow distribution of the anode electrolyte can be maintained respectively. As shown in FIG. 20B, arranging the main ribs 2080 such that the boundary of the negative support area (eg, dashed line 2088) is outside the boundary of the positive support area (eg, dashed line 2068) allows the positive and negative It increases the risk of buckling or distorting the electrolyte flow field, which can reduce the plating capacity, plating quality, ion exchange rate, and electrolyte flow, thereby reducing the performance of the redox flow battery. lower the

In another example, primary ribs 2030 may be positioned opposite positive flow field plate ribs 2012 such that the negative and positive support areas partially overlap. Partially overlapping the negative support area and the positive support area is such that the portion of the negative support area within the boundary of the positive support area is greater than the threshold overlap. may include placing the main rib 2030 opposite to the . For example, the threshold overlap is such that more than half (eg, greater than 50%) of the negative support area falls within the boundaries of the positive support area, with the main rib 2030 opposite the positive flow field plate rib 2012. placing. If the partial overlap between the negative and positive support regions is less than the threshold overlap, the risk of buckling and contraction of the anode and cathode electrolyte flow fields and damage to the cathode can be increased. As noted above, the positive flow field plate ribs 2012 may be interdigitated, serpentine, and parallel, as well as other configurations. Therefore, the number, pitch (spacing), and widthwise dimension (eg, x-direction) of the main ribs 2030 of the negative electrode spacer 2026 are such that the main ribs 2030 are aligned in the opposite direction to the positive flow field plate ribs 2012. can be selected for ease of use. In other words, the placement, primary rib pitch, and primary rib dimensions are such that, based on the design and configuration of the positive flow field plate, it adequately supports the loads and compressions of the positive and negative electrolyte flow fields. can be selected and adjusted accordingly.

16, an example configuration of a negative electrode spacer 1600 includes a plurality of major ribs 1620 oriented more parallel to the electrode length 1602 (e.g., y direction) and an electrode width 1604 (e.g., x direction). In this way, the support ribs can be oriented transversely to the main ribs 1620 and the main ribs 1620 can be oriented more parallel to the opposite positive flow field plate ribs 2012 across the membrane 2020 . can be attached. For the example of anode spacer 1600 shown in FIG. 16, when main rib 1620 is perpendicular to support rib 1640, the main rib length is given by electrode spacer length 1602, and the support rib length is the electrode spacer length. It is given by width 1604 . The number of main ribs 1620 may be greater than the number of support ribs 1640 , as shown in the example of anode spacer 1600 . In other cases, the number of main ribs 1620 may be less than the number of support ribs 1640 . Reducing the number of support ribs 1640 increases the functional electrode active area, thereby increasing the plating throughput, reducing the spread of the current density distribution across the electrodes during charging and discharging of the redox flow battery, which can help reduce the risk of short circuits and electrode deterioration. The main ribs 1620 and support ribs 1640 may be rigid and may be joined at their intersections to form a regular array of equally spaced and uniformly sized openings 1630 in the electrode. In particular, main ribs 1620 and support ribs 1640 accommodate nonwoven frameworks, spacers, supports, braces, scaffolds, underpinnings, or negative electrolyte flow fields between the plated flow field plate and the membrane. The nonwovens may also be joined or connected to form other types of support structures that maintain spacing between them.

FIG. 17A shows an enlarged plan view 1700 of Detail A of anode spacer 1600 showing regular, evenly spaced, and evenly sized openings 1630 in anode spacer 1600 . The spacing between consecutive adjacent main ribs, main rib pitch 1704, and the spacing between consecutive adjacent support ribs, support rib pitch 1702, define the number of joints 1706 between the main ribs and the support ribs. In the negative electrode spacer 1600 example, the supporting rib pitch 1702 is larger than the main rib pitch 1704 and creates an elongated opening 1630 along the electrode length 1602 to increase the active area available for plating. In other examples, the support rib pitch 1702 and the main rib pitch 1704 can be equal, resulting in square openings 1630, or the support rib pitch 1702 can be smaller than the main rib pitch 1704, resulting in elongated openings 1630 in the electrode width 1604 direction. . Support rib pitch 1702 and main rib pitch 1704 also define the aperture density (opening area: support rib and main rib area) of anode spacer 1600 . Support rib pitch 1702 and main rib pitch 1704 may be selected such that the aperture density is greater than the threshold aperture density. The threshold aperture density may correspond to an aperture density at which sufficient electrode plating can be supported to accommodate the desired redox flow battery cell capacity. Decreasing the aperture density (e.g., increasing the supporting rib pitch 1702 and increasing the main rib pitch 1704) below the threshold aperture density can reduce the plating throughput of the anode spacer 1600, thereby reducing the redox flow battery. The charge/discharge capacity of the cell may decrease.

The desired charge/discharge capacity of the redox flow battery cell may be determined by the desired energy capacity of the redox flow battery system. For example, if the desired battery charge capacity is increased from 4 hours to 8 hours, the open density can be increased to increase the plating throughput of the anode spacer 1600 . Increasing the aperture density can reduce the stiffness of the anode spacer 1600 . Accordingly, the structural stiffness of one or more of the main ribs 1620 and/or the support ribs 1640 can be increased as the aperture density increases. In one example, increasing the main rib thickness 1718 and/or the support rib thickness 1712 can increase the structural rigidity of the anode spacer 1600 . In this way, the redox flow battery cell capacity can be increased while maintaining the structural rigidity of the anode spacer 1600 . Main rib thickness 1718 may be greater than support rib thickness 1712 , or main rib thickness 1718 may be less than support rib thickness 1712 . Having the main rib thickness 1718 thicker than the support rib thickness 1712 can help increase the spacing between the plating electrode and the plating flow field plate to accommodate higher flow rates of the plating electrolyte. In addition, having primary rib thickness 1718 greater than support rib thickness 1712 helps increase the structural rigidity of the plating electrode.

Reference is now made to FIG. 17B, which shows section 1710 of section BB of FIG. 17A. As described above, the main ribs 1620 can be positioned toward the substrate side (e.g., the negative flow field plate side) 1719 of the anode spacer 1600 and the support ribs 1640 can be positioned toward the membrane side 1711 of the anode spacer 1600. can do. The main ribs 1620 can extend apart (in the z-direction) and project from the membrane side 1711 of the support ribs 1640 towards the substrate side 1719 . As shown in the example of FIG. 17B, main rib 1620 can extend from support rib 1640 according to a distance defined by the difference between main rib thickness 1718 and support rib thickness 1712 . By extending from the support ribs 1640 toward the substrate side 1719 of the anode spacer 1600, the main ribs 1620 can increase the plating active area on the anode and provide structural support for the electrode stack assembly. can. Further, the main ribs 1620 reduce buckling of the anode electrolyte flow field and maintain anode electrolyte flow in the anode electrolyte flow field when sandwiching the anode between the membrane and the negative flow field plate. Helpful. As described above with reference to FIG. 17A, increasing the support rib thickness 1712 and/or the main rib thickness 1718 can help increase the structural rigidity of the anode spacer 1600. FIG.

Additionally, main rib 1620 may extend away from support rib 1640 at a main rib draft angle 1716 (eg, in the xz plane). In some examples, main ribs 1620 may extend perpendicularly from support ribs 1640 . In another example, the main rib draft 1716 may be ±3° from vertical with respect to the support ribs 1640 . In yet another example, main rib draft 1716 may be ±10° from normal to support ribs 1640 . If the primary ribs form an acute angle with the negative flow field plate 2040 (eg, the plating surface), the primary ribs form a sharp angle between the membrane and the plating surface, as described below with reference to Figures 21A-21C. Electrolyte current flow can be interrupted. Blocking can create a gradient in the electrolyte current density reaching the plating surface, thus creating a higher dispersion of current distribution and plating density in the negative flow field plate. Depending on manufacturing capabilities, the main rib draft 1716 of the anode spacer 1600 can form a non-perpendicular angle with the support ribs 1640, resulting in some blocking and current density gradients. Therefore, reducing the deviation from 90° of the main rib draft angle 1716 can help reduce the current density gradient during charging of the redox flow battery.

17C, a cross-sectional view of section CC (eg, support rib 1640) of FIG. 17A, including support rib radius 1724 and support rib draft 1722, is shown. As shown in FIG. 17C, the support ribs 1640 may be positioned closer to the membrane side of the anode spacer 1600, even though they are semi-circular in cross-section with a support rib radius 1724 less than the main rib thickness 1718. good. Support rib draft 1722 may refer to the angle (xy plane) between main rib 1620 and support rib 1640 . For example, if the support ribs 1640 are oriented vertically, the support rib draft may be 0°. As shown in Table 2, the support rib length 1724 may be between 0.25 mm and 25 mm, and the support rib draft angle may be -10° to +10°. Referring to FIG. 17D, a cross-sectional view 1730 of section DD of FIG. 16 is shown. Cross-sectional view 1730 applies to the extreme support ribs 1642 and 1648 of anode spacer 1600 . The extreme support ribs 1642 and 1648 may be formed with a draft angle 1732 transverse to the vertical. When the lateral draft 1732 is 90°, the extreme support ribs 1642 and 1648 are oriented vertically. When the lateral draft angle 1732 is greater than 90°, the extreme support ribs 1642 and 1648 slope inward, and when the lateral draft angle 1732 is less than 90°, the extreme support ribs 1642 and 1648 slope outward. do. The formation of the acute lateral draft 1732 can assist passage of electrolyte fluid (eg, liquid or gas) in the flow direction of the plating electrolyte flow field. However, forming the lateral draft to be less than the threshold lateral draft can increase manufacturing complexity and cost, and can reduce the mechanical strength of the plating electrode due to the presence of sharper edges. It can increase the risk of failure. 17E, a cross-sectional view 1740 of section EE of FIG. 16 is shown. Cross-sectional view 1740 applies to extreme major ribs 1622 and 1628 of anode spacer 1600 . The extreme main ribs 1622 and 1628 may be formed with a main rib draft 1742 with respect to vertical. When the main rib draft 1742 is 90°, the extreme main ribs 1622 and 1628 are oriented vertically. When the main rib draft 1742 is greater than 90°, the extreme main ribs 1622 and 1628 slope inward, and when the main rib draft 1742 is less than 90°, the extreme major ribs 1622 and 1628 slope outward. do. Deviations from 90° in main rib draft 1742 can increase current density and plating gradients during charging.

Table 2 shows the length of the main rib, the pitch of the main rib, the height of the main rib, the draft of the main rib, the width of the supporting rib, the thickness of the supporting rib, the pitch of the supporting rib, the draft of the supporting rib, and the support Examples of values for various electrode configuration features, such as rib length and electrode width-to-length ratio, are shown. The main rib draft and/or the support rib draft can be selected to accommodate electrode forming processes including injection molding and roll-to-roll processing. The main ribs and support ribs are not necessarily identical in size, shape and/or cross-section. For example, one or more of the main or support ribs may vary in length, thickness, placement, and the like. In particular, in some example electrode configurations, primary ribs may include different values of draft relative to adjacent primary ribs. In other examples, the thickness of the main ribs may extend beyond the support ribs toward the membrane or toward the flow field plate. In other examples, some of the thicknesses of the main ribs may extend beyond the support ribs on the membrane side of the electrode, while other thicknesses of the main ribs extend beyond the support ribs on the substrate side of the electrode. may be extended. If the thickness of the main ribs extends beyond the support ribs 1640 on the substrate side of the electrode, the surface area of the membrane available for electrolyte is increased, which can increase the charge/discharge rate of the redox flow battery. Moreover, as further described below with reference to FIGS. 12-13, placing the support ribs 1640 closer to the membrane than the plating surface (eg, negative flow field plate) reduces the current density at the plating surface. It can help reduce the variance of the distribution.

21A-21C, these figures show partial cross-sectional views of the electrode stack assembly, including the anode spacer 2026, the main ribs, and the negative side of the membrane 2020 (opposite the positive redox side 2102). side) of the negative flow field plate 2040. The main rib 2130 includes a lateral cross-section (xy plane) that is constant along the z-direction. Stated another way, the cross-section of the main rib may be constant along an axis perpendicular to the plane of the electrode assembly stack layers. In other words, the major rib cross-section 2128 at the membrane is equivalent to the major rib cross-section 2129 at the plating surface, and there are no undercuts in the major ribs (as described with reference to Figure 21C). Thus, electrolyte fluid and ionic current flow indicated by dashed arrows 2150 from the membrane 2020 to the plating surface (negative flow field plate 2040) can be unimpeded and transported across the surface of the main ribs 2130 to can be distributed and distributed more uniformly across the plane of (eg, the xy plane). In other words, anode spacers 2026 comprising primary ribs 2130 with constant cross-section from membrane 2020 to the plating surface can help reduce ion concentration gradients and current intensity gradients in the anode electrolyte flow field.

In contrast, the primary rib 2132 includes a cross section (in the xy plane) that varies continuously along the z-direction. Stated another way, the main rib cross-section decreases monotonically from membrane 2020 to the plating surface. In other words, the main rib cross-section 2131 in the film may be larger (or smaller for other examples of r) than the main rib cross-section 2133 in the plating. Thus, the larger main rib cross-section 2131 partially blocks the plating surface, and the flow of electrolyte fluid and ionic current indicated by dashed arrows 2152 is directed from the membrane 2020 to the plating surface (negative flow field). plate 2040), thereby introducing electrolyte concentration and current gradients. Therefore, electrolyte fluid and ionic current flow, indicated by dashed arrows 2152 from membrane 2020 to the plating surface (negative flow field plate 2040), is more non-uniform across the plane of the plating surface (eg, the xy plane). can be dispersed and distributed in Referring now to FIG. 21C, primary rib 2134 includes a primary rib having non-constant cross-section 2133 between membrane 2020 and a plating surface (eg, negative flow field plate 2040). In particular, although the main rib cross-section 2133 at the plating surface of the main rib 2134 and the cross-section 2133 at the membrane are comparable, the cross-section of the main rib 2134 further includes an undercut 2136 . The undercuts 2136 may be formed by protrusions (eg, posts) 2137 that extend at least partially in the lateral x-direction (eg, having an x-component) from the main ribs. The protrusions 2137 can include various geometries and shapes extending from the main ribs, including rounded squares, fingers, chevrons, etc. (as shown in FIG. 21C). The presence of protrusions 2137 can block part of the plating surface. In other words, protrusions 2137 may block direct flow from membrane 2020 to blocked portions of the plating surface. Such electrolyte fluid and ionic current must flow around protrusion 2137 in order to reach the volume of undercut 2136 and the adjacent plating surface (as indicated by dashed arrow 2154). Additionally, some of the flow can be blocked by protrusions 2137, further increasing the gradient of electrolyte ion concentration and current between the membrane and the plating surface.

Since kinetic losses can be scaled exponentially with available electrode surface area, current distribution can also have a large impact on cell performance. In addition, poor (more uneven, more uneven, more uneven) current distribution across the electrode active area (eg, plating surface) can increase the risk of short circuits in redox flow battery cells. For redox flow battery cells operating at higher plating densities, reducing the current density variance (e.g., diffusion) reduces the risk of shorting the battery cells, as shown in table 1100 of FIG. can help slow down and reduce Current density variance can be evaluated by examining the interquartile range (IQR) of the current density and the mean absolute deviation (MAD) of the current density. Maintaining an IQR<2.0 on the plated substrate while maintaining a MAD<0.2 on the plated substrate (e.g., plated electrode substrate) can help substantially reduce the risk of battery short circuits. can. As shown in the second and third rows of table 1100, for MAD=4 and IQR=10, and for MAD=8 and IQR=20, for MAD=0 and IQR=0 (see Table 1100). 1100 top), the variance of the current distribution is higher and can start spreading into the electrode gap early (eg, T1, T2, Tn), leading to premature cell shorting.

Ten different anode spacer configurations, shown in Tables 1200 and 1300 of FIGS. 12 and 13, respectively, were evaluated according to the following criteria. Anode spacer configurations can be manufactured by injection molding and/or roll-to-roll processing. The negative electrode spacer material is compatible with the operating conditions of the electrolyte and redox flow battery cell. Manufacturing costs are less than $30/kW. The current density of the plating electrode on the plating substrate is IQR<2.0. The current density of the plating electrode on the plating substrate is MAD<0.2. The area specific resistance (ASR) of the plating electrode on the plating substrate is ≦0.9Ω-cm ² . The negative electrode spacer support provides adequate structural support for the positive electrode (see details below). Bubbles generated during cell operation can be swept away without additional treatment (electrodes must exhibit some degree of hydrophobicity). Rev. AJ (eg, corresponding to anode spacer configurations 1210, 1220, 1230, 1240, 1250, 1310, 1320, 1330, and 1340, respectively) can be manufactured by injection molding, whereas Rev. K (negative spacer configuration 1350) can be manufactured by roll-to-roll processing.

As shown in Tables 1200 and 1300, the Rev. G, I, J and K denote the variance of the current density distribution satisfying the criteria IQR<2.0, MAD<0.2, and ASR≦0.9 ohm-cm ² . The rightmost columns of Tables 1200 and 1300 show 2D plots of the current density distribution at 45 mA/cm ² at the plating surface (xy plane) adjacent to the repeating element of each anode spacer configuration. Repeating elements 1212, 1222, 1232, 1242, 1252, 1312, 1322, 1332, 1342 and 1352 are described in Rev. Repeating structures within the anode spacer configuration of A, B, C, D, E, F, G, H, I, J, K, centered at the intersection of the support rib and the main rib and extending half the support rib pitch. They extend in both width directions (y-direction) and half the main rib pitch in both width directions (x-direction), respectively. Enlarged plan views of the negative electrode spacer configurations and their corresponding repeating units are shown in FIGS. 23A-23K, respectively. The current intensity at each point of the current density distribution is indicated by color, with red areas indicating higher current intensities and blue areas indicating lower current intensities. The gray area indicates the inactive area where the main and support ribs of the anode spacer contact the plating surface.

As shown by the current density distributions of repeating elements 1210, 1220, 1230, 1240, and 1250, anode spacer configurations A-F, which include undercuts in the main ribs and shaded areas below them, exhibit high current densities. Shows dispersion of higher current density distributions, including non-uniform and non-uniform regions where regions can be adjacent to low current density regions. For example, in configuration A, a current density gradient is observed around the undercut regions along the main rib between the inactive regions 1214 where the main rib is not undercut and contacts the plating surface. Similar current density gradients occur for configurations B, C, D, and F, all of which contain structural features of undercuts in the main ribs of the corresponding repeat units. These current density gradients are even more pronounced in anode spacer configurations C and D, where the support ribs are located on the substrate side of the main ribs. In fact, placing the support ribs on the substrate side of the main rib undercuts the main rib along its entire length, resulting in a higher current density gradient. Additionally, by locating the support ribs on the substrate side of the negative spacer, the portions of the plating surface that contact the support ribs are inactive, as shown by inactive regions 1236 and 1246 . In other words, placing the support ribs on the membrane side of the anode spacer can help reduce current density gradients at the plating surface during charging and discharging.

As described above with reference to FIGS. 21A-21C, structural features within the main ribs, such as undercuts and protrusions that extend at least partially in the x-direction, result in higher current density distribution due to interruption. can increase the risk of dispersion of ions and create gradients in electrolyte ion flux, concentration, and current. In contrast, anode spacer configurations G, I, and J include solid monolithic primary ribs with no undercuts or protrusions and a primary rib draft of 0 degrees from normal to the support ribs. Thus, blockage near the area where the primary rib contacts the plating surface is reduced and current gradients in the area where the primary rib contacts the plating surface are substantially eliminated. Rev. K includes monolithic primary ribs with no undercuts or protrusions, but because of manufacturability, the draft angle of the primary ribs is less than perpendicular to the support ribs, so that near the interrupted portion of the plating surface , and a current density gradient 1354 occurs. Rev. H (negative electrode spacer configuration 1320) includes cylindrical primary ribs with a circular cross-section. Thus, the electrolyte current converges and diverges as it flows from the film around the main ribs until it reaches the plating surface, thereby creating an electrolyte concentration gradient and reducing Increase the dispersion of the current density distribution.

Current gradient regions 1216, 1226, 1236, 1246, 1256, 1316, 1326, 1336, 1346 and 1356 are also observed to be associated with each of the support ribs. Therefore, reducing the number of lateral support ribs (eg, increasing the support rib pitch) can also help reduce the current density and reduce the dispersion of the current density distribution. Decreasing the number of primary ribs (e.g., increasing the primary rib pitch) reduces the negative electrode spacer configuration 1310 (the primary ribs corresponding to all positive flow field plate ribs) and the negative electrode spacer configuration 1330 (the alternate positive flow field plate ribs). The main ribs corresponding to the field plate ribs) can further help to reduce the current density and reduce the spread of the current density distribution, as evident from the comparison. A reduction in the number of primary ribs reduces the spread of the current density distribution to the extent that it can provide sufficient structural support to the electrode stack assembly during compression after battery cell assembly and during battery cycling (charging and discharging). can help you to In particular, the electrode spacer configuration can remain sufficiently rigid so that it does not buckle from compression when the redox flow battery system is assembled. In one example, the main ribs may be located on the negative side of the membrane of the redox flow battery cell, facing every other rib (eg, alternating) of the comb flow plate on the positive side of the membrane.

Current density distributions for ten different anode configurations (Rev. AK) are also plotted in boxplot 1400 of FIG. Boxplot 1400 plots the current density distribution as quartiles. The shaded box is the median of the current density distribution (indicated by the dashed line) within the box bounded by the highest first quartile value and the lowest third quartile value (shaded box). indicates Whiskers outside the bounds of the box represent the upper and lower endpoints of the quartile distribution. Outliers outside the whiskers are represented as unshaded rectangles. Rev. G, I, J, K are represented by small boxes and short whiskers with some outliers, indicating narrower (lower variance) current density distributions. Rev. The current density distribution of I is preferred because it is narrower and has fewer outliers (less extreme).

Referring now to FIG. 15, various electrode configurations: Rev. A plot 1500 is shown showing cell validation testing for C, G, and J, Ti mesh electrode configurations, as well as a commercial electrode. The Ti mesh initially has a low charge voltage, but shows short-circuit behavior at about 6 hours of charge, where the cell voltage begins to decrease as the charge current increases with time, thereby increasing the Rev. Shows worse performance compared to C, G, and J.

Referring now to Figure 24A, an exploded plan view of an alternative representation of a negative electrode spacer assembly 2400 for a redox flow battery is shown. Anode spacer assembly 2400 may be positioned in the redox flow cell stack assembly such that anode spacer assembly 2400 is sandwiched and inserted between the membrane and the negative flow field plate. Anode spacer assembly 2400 includes anode spacer 2420 integrated with membrane 2410 by attaching anode spacer 2420 to the negative side of membrane 2410 (indicated by arrow 2414). Integrating the anode spacers 2420 with the membrane 2410 reduces the number of separate components (e.g., layers) to align and maintains alignment between the active regions of the anode spacers 2420 and the membrane 2410, thereby reducing redox. It can help facilitate assembly of the flow cell stack. The active area of the anode spacer 2420 can refer to the area of the anode spacer 2420 defined by the main ribs 2426 and the support ribs 2428, where the anode electrolyte flows in contact between the membrane and the negative flow field plate, This is the region where electrolyte species participate in redox reactions. The negative electrode spacer may further include an inactive perimeter region 2422 surrounding the active region where redox reactions do not occur when in contact with the electrolyte. Membrane 2410 may be attached to anode spacer 2420 by attaching edge region 2416 of membrane 2410 to inactive peripheral region 2422 of anode spacer 2420 . The dimensions of edge region 2416 can be slightly larger than the dimensions of the active area of membrane 2410 (or slightly larger than the inner perimeter of inactive area 2422). Additionally, attaching the edge region 2416 to the inactive peripheral region 2422 may include aligning the edge region 2416 of the membrane 2410 outside the active region of the negative electrode spacer 2420 . Thus, when membrane 2410 is integrated with anode spacer 2420 , the membrane covers the entire active area of anode spacer 2420 . In one example, edge region 2416 of membrane 2410 can be heat-sealed to anode spacer 2420 .

Referring now to FIG. 24B, a plan view of anode spacer 2420 is shown. Negative electrode spacer 2420 can include a plurality of inlet and outlet openings 2402 disposed in inactive peripheral region 2422 . Electrolyte fluid is transported from the inlet to the negative flow field and from the negative flow field to the outlet via various channels or channels integrated into the layers of the electrode stack assembly, including the anode spacer. obtain. The dimensions of the active area are indicated by the length of the active area and the width of the active area. If the main ribs 2426 are oriented parallel to the length of the negative electrode spacer (y-axis), the length of the main ribs corresponds to the length of the active region. If the support ribs 2428 are oriented parallel to the width of the anode spacer (x-axis), the length of the support ribs corresponds to the active area width.

Referring now to FIG. 24C, a cross-sectional view of negative electrode separator 2420 at cross-section BB is shown. As described above with reference to FIG. 24A, edge region 2416 may be attached to negative electrode separator 2420 at the inner perimeter of inactive peripheral region 2422 . The thickness of the negative electrode separator 2422 may be similar to the thickness of the major ribs (including the edge major ribs 2425). The primary rib may extend from the support rib distally from the membrane (y-direction) at the draft of the primary rib with respect to the support rib (xy plane). Depending on manufacturing capabilities, the primary rib draft angle can be acute within 90°±10° or ±3°. When the main rib draft is close to 90°, the current density distribution is less distributed at the plating surface than when the main rib draft is much less than 90°. Within the active region of the negative electrode configuration, the center thickness includes the film thickness 2412 in addition to the main rib thickness. Inactive peripheral region 2422 may be constructed of a non-conductive rigid material. Each of the main ribs 2426 and support ribs 2428 may be attached to the inner perimeter of the inactive peripheral region 2422 . For example, the longitudinal ends of the plurality of main ribs and the widthwise ends of the plurality of support ribs may be attached to the rigid framework of the inactive perimeter region 2422 . In this way, the inactive peripheral region 2422 can provide structural integrity to the main ribs 2426 and support ribs 2428 and the membrane 2410, thereby maintaining planarity and also allowing the main ribs 2426 and support ribs 2426 and support ribs 2428 to maintain planarity. Helps maintain the relative position of 2428 as well as membrane 2410 . In some examples, the additional structural support provided by attaching the primary ribs 2426 and support ribs 2428 to the inactive peripheral region 2422 reduces the thickness of one or more of the primary ribs 2426 and support ribs 2428. , or increasing the pitch of one or more of the main ribs 2426 and support ribs 2428 can help improve the performance of the redox flow battery system. As noted above, reducing the thickness of the main ribs 2426 and support ribs 2428 can help reduce current density gradients at the plating surface, which can reduce resistive losses in the thickness of the electrode stack assembly. can be reduced.

Referring now to FIG. 25A, a top view of another alternative representation of an electrode configuration including negative electrode spacers 2500 is shown. A negative electrode spacer 2500 may be placed in the redox flow cell stack assembly between the membrane and the negative flow field plate. Anode spacer 2500 has a plurality of main ribs 2526 oriented more parallel to the length of the active region and a plurality of support ribs 2528 oriented more parallel to the width of the active region. Including area. The active area of the anode spacer 2500 can refer to the area of the anode spacer 2500 defined by the main ribs 2526 and the support ribs 2528, where the anode electrolyte flows through the membrane and the negative flow field in the redox flow battery stack assembly. In contact with and flowing between the plates, electrolyte species participate in redox reactions. The negative electrode spacer 2500 may further include an inactive peripheral region 2522 surrounding the active region where redox reactions do not occur when in contact with the electrolyte. Anode spacer 2500 can include a plurality of inlet and outlet openings 2502 disposed within inactive peripheral region 2522 . Electrolyte fluid is transported from the inlet to the negative flow field and from the negative flow field to the outlet through various channels 2524 or flow paths integrated into the layers of the electrode stack assembly, including the anode spacer. can be exposed. If the main ribs 2526 are oriented parallel to the length (y-axis) of the anode spacer, the length of the main ribs corresponds to the length of the active region. If the support ribs 2528 are oriented parallel to the width (x-axis) of the anode spacer, the length of the support ribs corresponds to the width of the active area.

Next, referring to FIG. 25B, an AA cross-sectional view of negative electrode separator 2500 is shown. The center thickness of the negative electrode separator 2500 may be similar to the main rib thickness. The main rib 2526 may extend from the support rib 2528 distally from the membrane (y-direction) in the redox stack assembly at the draft of the main rib with respect to the support rib (xy plane). Depending on manufacturing capabilities, the primary rib draft angle can be acute within 90°±10° or ±3°. When the main rib draft is close to 90°, the current density distribution is less distributed at the plating surface than when the main rib draft is much less than 90°. Inactive peripheral region 2522 includes a border region 2550 that can be constructed of a non-conductive rigid material and extends like a picture frame around negative electrode spacer 2500 . Boundary region 2550 can include an outer corrugated frame that includes longitudinal channels 2552 in the top and bottom surfaces of the corrugated frame. Corrugations and channels 2552 can reduce the weight and material cost of anode spacer 2500 while maintaining structural rigidity. The corrugated frame 2550 can be positioned outside the active area of the anode spacer. The border region can further include a lip 2554 extending inwardly from the perimeter of the anode spacer 2500 . Each of the main ribs 2526 and support ribs 2528 may be attached to a lip. For example, the longitudinal ends of the plurality of main ribs and the widthwise ends of the plurality of support ribs may be attached to lips 2554 (eg, rigid frame lip structures) of the inactive perimeter region 2422 . The thickness of lip 2554 may correspond to the center thickness of the active region. In this manner, the negative flow field plate 2560 may be attached to a picture frame in which the outer edge of the negative flow field plate 2560 may be attached below the lip 2554 . When attached to a picture frame, the membrane-facing surface of the negative flow field plate may simply contact the membrane-tips of the main ribs 2526 and thus the negative flow field plate during assembly of the redox flow cell stack. When 2560 is compressed toward the membrane, major ribs 2526 support and maintain the thickness dimension of the anode electrolyte flow field. In this way, the inactive peripheral region 2522 and border region 2550 can provide structural integrity to the main and support ribs 2526 and 2528 and the negative flow field plate 2560, thereby maintaining planarity, and aids in the relative alignment of main ribs 2526 , support ribs 2528 and negative flow field plate 2560 . In some examples, the additional structural support provided by attaching primary ribs 2526 and support ribs 2528 to inert peripheral region 2522 and boundary region 2550 may be provided by one or more of primary ribs 2526 and support ribs 2528. By allowing the thickness to be reduced or the pitch of one or more of the main ribs 2526 and the support ribs 2528 to be increased, the performance of the redox flow battery system is improved. can help. As noted above, reducing the thickness of the main ribs 2526 and support ribs 2528 can help reduce current density gradients at the plating surface and also allows for lower resistive losses in the thickness of the electrode stack assembly. can be reduced.

Referring now to Figure 19, a flowchart of a method 1900 of assembling a redox flow battery is shown. Method 1900 begins at step 1910 in which a plating electrode spacer can be formed by forming a plurality of primary ribs laterally connected to a plurality of support ribs. Forming the plating electrode spacers can include injection molding the main ribs and/or support ribs or forming the main ribs and/or support ribs by roll-to-roll processing. Other manufacturing methods for forming the primary ribs and/or support ribs include thermoforming, selective laser sintering (SLS), die cutting, extrusion, machining, or other polymer manufacturing processes. As noted above, the plurality of main ribs may be oriented more parallel to the length of the plating electrode, and the plurality of support ribs more transverse to the length of the plating electrode (e.g. , more parallel to the width of the plating electrode). The plating electrode arrangement can include plating electrode spacers and plating flow field plates. Each of the main ribs may be connected to each of the support ribs at a junction therebetween to form an array of regular, equally spaced, uniformly sized openings. The pitch of the main ribs can range from 0.5 mm to the width of the plating electrode. When the pitch of the main ribs includes the width of the plating electrode, the number of main ribs is two and each main rib constitutes the endmost main rib. The pitch of the support ribs can range from 0.25 to the length of the plating electrode. When the pitch of the support ribs includes the length of the plating electrode, the number of support ribs is two and each support rib constitutes the endmost support rib.

As described above with reference to FIGS. 16 and 17A-E, the main ribs and support ribs of the plating electrode spacer can be formed with characteristics according to the range of values shown in Table 2. The values of the main rib and support rib features are selected to provide the desired structural stiffness, distribution of current density distribution, plating electrode spacer opening density, electrode plating throughput, and other electrode properties, as described above. be able to. As a further example, the primary rib geometry can be configured to provide desired flow characteristics of the electrolyte fluid, which can include liquids and/or gases (e.g., reduced fluid stagnation in the plating flow field). . By forming the main ribs and supporting ribs in this manner, the performance of the redox flow battery system can be improved while maintaining the durability and useful life of the plating electrode. For example, the features of the main ribs and support ribs can be selected to withstand contact pressures applied thereto. The contact pressure of each main or support rib can be defined by dividing the load (in Newtons, N) applied to the active area by the contact area (mm ² ) of the main and support ribs. In other words, each main rib and support rib should provide sufficient structural rigidity to support the normal functioning of the redox flow battery cell and reduce the risk of deflection of the main rib and support ribs due to fluid pressure fluctuations. can be done. In one example, the features of the main ribs and support ribs can be selected to withstand contact pressures of 1.5 MPa or 0.1-10 MPa. In particular, the thickness of the support width supports the main ribs during handling, assembly, and installation of the battery, accommodates the desired flow rate of the electrolyte through the flow field of the plating electrolyte, and provides the desired plating treatment of the negative electrode. You can choose to match your abilities. Increasing the thickness of the primary ribs can increase the volume to accommodate the desired flow rate of the plating electrolyte; however, increasing the thickness of the primary ribs can also increase the resistance of the battery cell, increasing the Charge/discharge performance may deteriorate. Reducing the thickness of the main ribs can reduce the volume to accommodate the desired flow rate of the plating electrolyte; however, reducing the thickness of the main ribs also reduces the resistance of the battery cell, It is possible to improve the charge/discharge performance of the battery.

Method 1900 then continues to 1920 where plating electrode spacers may be formed from a non-conductive material. Non-limiting examples of non-conductive materials include thermoplastic resins such as high impact polystyrene, polypropylene, polytetrafluoroethylene, high density polyethylene, ultra high molecular weight polyethylene, polycarbonate; polyesters, vinyl esters, epoxies, etc. FR4 glass fiber and G10 glass fiber, or fiber reinforced plastics such as fiber reinforced sheets; and ethylene-propylene diene monomer rubber, Santoprene, silicone, styrene-butadiene rubber, Buna- N (buna-N), rubbers such as thermoplastic olefin rubbers, and the like. Alternatively, the plating electrode may be formed of a non-conductive material without applying a conductive paint or coating. In addition, the material of the plating electrode exhibits sufficient structural rigidity so that it does not substantially deform under contact pressures of up to 1.5 MPa, or as high as 0.1 MPa to 10 MPa over the product lifetime (eg, greater than 25 years). You can choose to keep Forming the plating electrode spacers from a non-conductive material includes forming the plating electrode spacers without coating the plating electrode spacers with a conductive coating.

The method 1900 continues at step 1930 where a plating electrode (negative) spacer is inserted between the membrane and the plating (negative) flow field plate on the plating (negative) side of the membrane. Thus, the plating (negative) electrolyte flow channel is sandwiched between the membrane and the plating flow field plate and supported by plating electrode spacers, as shown in FIG. 20A. When the negative flow field plate comprises a flat negative flow field plate, the membrane-facing side of the negative flow field plate is a continuous flat plate having no protrusions or openings or other discontinuities. It may be the surface. Additionally, the flat plating flow field plate does not have IDFF channels to form the plating electrolyte flow field. In another aspect, the plating flow field plate and the membrane are separated by main ribs sandwiching the non-comb plating electrolyte flow field therebetween. In some expressions, placing a plating electrode spacer between the membrane and the plating flow field plate on the plating side of the membrane faces the plating flow field plate as described above with reference to FIGS. and attaching the membrane to the plating electrode spacers. In other words, the main ribs and supporting ribs of the plating electrode spacer can be attached to the picture frame structure. Additionally, the negative flow field plate may be attached to the picture frame structure on the opposite side of the main and support ribs from the membrane-facing side. The method 1900 continues to 1940 where a redox electrode (positive electrode) is inserted between the membrane on the redox (positive) side of the membrane and the redox (positive) flow field plate. This sandwiches the redox (positive) electrolyte flow field between the redox electrode and the redox flow field plate, as shown in FIG. 20A.

At 1950, the main rib of the plating electrode spacer is aligned with the rib of the redox flow field plate across the membrane in the electrode stack assembly and aligned with the rib of the redox flow field plate as shown in FIG. 20B. are oriented more parallel to each other. When the redox electrode configuration includes interdigitated flow field plates, the main ribs are oriented more parallel to the ribs of the across-the-membrane IDFF plate. Thus, during assembly and operation of the redox flow battery, the main ribs of the plating electrode spacer are supported oppositely by the ribs of the redox flow field plate across the membrane. Thus, when the plating flow field plate and the redox flow field plate are compressed toward the membrane, the plating electrolyte flow field maintains its shape and flow. Method 1900 continues to 1960 where metal is plated from the plating electrolyte to the plating flow field plate. In particular, plating the plating electrode can include electrochemically depositing metal onto the surface of the plating flow field plate from reduced metal ions in the plating electrolyte. After 1960, method 1900 ends.

Thus, the redox flow battery comprises a first electrode disposed on a first side of the membrane and a second electrode disposed on a second side of the membrane opposite the first side. The inserted membrane and a first flow field plate including a plurality of positive flow field ribs, each of the plurality of positive flow field ribs extending at the first support region on the first side. In contact with one electrode, the second electrode includes an electrode spacer disposed between the membrane and the second flow field plate, the electrode spacer including a plurality of primary ribs, each of the plurality of primary ribs , the second flow field plate at second support areas on the second side, each of the second support areas being aligned opposite one of the plurality of first support areas. In one example, the second electrode can include a second flow field plate positioned on the second side to form a non-comb flow field between the second side and the second flow field plate. In another example, the second flow field plate can include a continuous flat surface having no protrusions, the continuous flat surface facing the electrode spacers and having a plurality of main surfaces at the second support region. contact each of the ribs. Additionally, the electrode spacer may include a plurality of support ribs, each of which may be oriented transversely to each of the primary ribs and in non-woven contact with one or more of the primary ribs. A plurality of primary ribs can protrude from the plurality of support ribs and extend away from the second side, and the plurality of primary ribs can be greater in number than the plurality of support ribs. In a further example, the electrode spacer may include a rigid frame surrounding the plurality of main ribs and the plurality of support ribs, the longitudinal ends of the plurality of main ribs and the widthwise ends of the plurality of support ribs attached to the rigid frame. be able to. Additionally, a second flow field plate may be attached to the rigid frame, the second flow field plate attached to the rigid frame having a continuous flat surface contacting the plurality of primary ribs at the second support area. obtain.

In another embodiment, a method of assembling a redox flow battery includes sandwiching a plating electrolyte flow field and a plating electrode spacer between the membrane and a plating flow field plate on the plating side of the membrane, the plating electrode spacer comprising a plurality of main ribs. may include including Additionally, the method can include sandwiching a redox electrolyte flow field between a redox electrode and a redox flow field plate on the redox side of the membrane, the redox electrode including a plurality of positive flow field ribs. Further, the method aligns each of the plurality of primary ribs with the plurality of positive flow field ribs and compresses the plating flow field plate and the redox flow field plate toward the membrane to substantially reduce the dimensions of the plating electrolyte flow field. main ribs being supported oppositely by opposite positive flow field ribs across the membrane. In one example, the method may include forming a plurality of primary ribs and forming a plurality of support ribs laterally connected in a non-woven manner to the plurality of primary ribs. Further, forming the plurality of main ribs and forming the plurality of support ribs can include forming the plurality of main ribs and the plurality of support ribs from a non-conductive material without a conductive coating. In another example, the method can include plating metal from the plating electrolyte onto the plating flow field plate during charging of the redox flow cell battery without plating the metal onto the plating electrode spacers. A further example may include integrating the plating electrode spacer with the membrane by attaching the plating electrode spacer to the membrane. Further, integrating the plating electrode spacer with the membrane can include heat sealing the membrane to the plating electrode spacer.

In another embodiment, the redox flow battery comprises a negative electrode spacer interposed between the negative side of the membrane and the negative flow field plate and a positive electrode spacer interposed between the positive side of the membrane and the positive flow field plate. and may include Further, the negative electrode spacer can include a plurality of major ribs, the positive electrode can include a plurality of positive flow field ribs aligned opposite the across-the-membrane main ribs, and the negative flow field plate can include: , a continuous flat plating surface facing the membrane, and a non-interdigitated anode electrolyte flow field sandwiched between the plating surface and the membrane. In one example, a negative electrode spacer can include a plurality of support ribs and an array of uniformly sized openings formed by laterally non-woven bonding of a plurality of main ribs to the plurality of support ribs. In another example, the primary rib may comprise a solid monolithic structure having a constant cross-section along the length of the primary rib. Additionally, the primary ribs may comprise a solid monolithic structure having a constant cross-section along an axis perpendicular to the plane of the negative flow field plate. Further, the pitch of the support ribs may be smaller than the pitch of the main ribs, and the plurality of main ribs may be oriented parallel to the width of the negative electrode, and the plurality of support ribs may be oriented parallel to the length of the negative electrode. Oriented.

In this way, novel redox flow battery systems can be provided that include larger electrode gaps, which can lead to higher plating current densities and battery charge capacities, higher electrolyte flows and bubble Incidence can be accommodated. In addition, current density distribution spread, ohmic losses, battery short circuits, and manufacturing and operating costs can be reduced. When the electrode spacers are rigidly attached to the perimeter region of the frame, the electrode spacers are imparted with enhanced structural integrity, thereby ensuring the planarity and integrity of the main and support ribs of the electrode spacers, as well as the membrane 2410. It can help maintain relative alignment. In some instances, the additional structural support provided by attaching the main ribs and support ribs to the inactive perimeter area may result in increased plating throughput, reduced dispersion of current density distribution at the plating surface, and redox flow. It can help reduce resistive losses in the battery system.

It is also understood that the configurations and routines disclosed herein are exemplary in nature and are not to be considered in a limiting sense as these particular embodiments are capable of many variations. would be For example, the techniques described above may be applied to other flow batteries. Constituents of the present disclosure include all novel and nonobvious combinations and subcombinations of the various systems and configurations and other features, functions, and/or properties disclosed herein.

The following claims particularly recite certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to "an" element or "a first" element or their equivalents. Such claims are to be understood to include the incorporation of one or more such elements and neither require nor exclude more than one such element. should. Other combinations and subcombinations of the disclosed features, functions, elements and/or properties may be claimed through amendment of the claims or through presentation of new claims in this or a related application.

Such claims, whether broader, narrower, equal, or different in scope than the original claims, are considered to be included within the subject matter of this disclosure.

This completes the description. Reading this, many changes and modifications will occur to those skilled in the art without departing from the spirit and scope of the description. For example, hybrid redox flow battery systems, all-iron hybrid redox flow battery systems, and other redox flow battery systems can all utilize the present description.

Claims (20)

a membrane interposed between a first electrode positioned adjacent to a first side of the membrane and a second electrode positioned on a second side of said membrane opposite said first side; When,
a first flow field plate including a plurality of positive flow field ribs, each of said plurality of positive flow field ribs connecting said first electrode at said first side first support region; contact,
The second electrode includes an electrode spacer positioned between the membrane and a second flow field plate, the electrode spacer including a plurality of main ribs, each of the plurality of main ribs being aligned with the second flow field plate. contacting the second flow field plate at two side second support areas, each of the second support areas aligned opposite one of the plurality of first support areas;
redox flow battery. The second electrode further includes a second flow field plate positioned on the second side to form a non-comb flow field between the second side and the second flow field plate. The redox flow battery of claim 1, wherein The second flow field plate includes a continuous planar surface having no protrusions, the continuous planar surface facing the electrode spacers and the plurality of primary ribs at the second support region. 3. The redox flow battery of claim 2, wherein the redox flow battery is in contact with each of the electrode spacer further comprising a plurality of support ribs;
4. The redox flow battery of claim 3, wherein each of said support ribs is oriented transversely to each of said main ribs and is coupled with one or more of said main ribs. 5. The redox flow battery of claim 4, wherein the plurality of primary ribs project from the plurality of support ribs and extend away from the second side. 6. The redox flow battery of claim 5, wherein the number of said plurality of main ribs is greater than the number of said plurality of support ribs. The electrode spacer further includes a rigid frame surrounding the plurality of main ribs and the plurality of support ribs, wherein the longitudinal ends of the plurality of main ribs and the width direction ends of the plurality of support ribs are connected to the rigid frame. 7. The redox flow battery of claim 6, attached to a said second flow field plate attached to said rigid frame;
8. The redox flow battery of claim 7, wherein the second flow field plate attached to the rigid frame has the continuous flat surface contacting the plurality of primary ribs at the second support area. sandwiching a plating electrolyte flow field and a plating electrode spacer between the membrane and a plating flow field plate on the plating side of the membrane, the plating electrode spacer comprising a plurality of primary ribs;
sandwiching a redox electrolyte flow field between a redox electrode and a redox flow field plate on the redox side of the membrane, the redox electrode comprising a plurality of positive flow field ribs; and
aligning each of the plurality of primary ribs with the plurality of positive flow field ribs and compressing the plating flow field plate and the redox flow field plate toward the membrane substantially reduces the dimensions of the plating electrolyte flow field; said main ribs being supported oppositely by said positive flow field ribs across said membrane without changing the
A method of assembling a redox flow battery. 10. The method of claim 9, further comprising forming the plurality of main ribs and forming a plurality of support ribs laterally connected to the plurality of main ribs. 3. The forming of the plurality of main ribs and the forming of the plurality of support ribs comprises forming the plurality of main ribs and the plurality of support ribs from a non-conductive material without a conductive coating. 10. The method according to 10. 12. The method of claim 11, further comprising plating metal from a plating electrolyte onto said plating flow field plate during charging of a redox flow cell battery without plating metal onto said plating electrode spacers. 13. The method of claim 12, further comprising integrating the plating electrode spacer with the membrane by attaching the plating electrode spacer to the membrane. 14. The method of claim 13, wherein integrating the plating electrode spacer with the membrane comprises heat sealing the membrane to the plating electrode spacer. a negative electrode spacer interposed between the negative side of the membrane and the negative flow field plate;
a positive electrode interposed between the positive side of the membrane and the positive flow field plate;
the negative electrode spacer includes a plurality of main ribs,
the positive electrode includes a plurality of positive flow field ribs aligned opposite a plurality of main ribs across the membrane; and
the negative flow field plate includes a continuous flat plating surface facing the membrane and a non-comb-shaped anode electrolyte flow field sandwiched between the plating surface and the membrane;
redox flow battery. The negative electrode spacer includes a plurality of supporting ribs,
and a row of uniformly sized openings formed by laterally connecting the plurality of main ribs to the plurality of support ribs. 17. The redox flow battery of claim 16, wherein said primary rib comprises a solid monolithic structure having a constant cross-section along the length of said primary rib. 18. The redox flow battery of Claim 17, wherein said primary rib comprises a solid monolithic structure having a constant cross-section along an axis perpendicular to the plane of said negative flow field plate. 19. The redox flow battery of claim 18, wherein the pitch of the support ribs is less than the pitch of the main ribs. 20. The redox flow battery of claim 19, wherein the plurality of main ribs are oriented parallel across the width of the negative electrode and the plurality of support ribs are oriented parallel across the length of the negative electrode.

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