Additive for electrochemical flow reactor

Abstract

The present invention relates to an electrochemical reactor, which may be a half-cell of a rechargeable battery, comprising a liquid electrolyte pumped through the half-cell and having an electrochemical system in which solids are deposited at electrodes when an electric current flows. The liquid comprises a high molecular weight polymer or viscoelastic surfactant that enables elastic turbulence to occur, and the half-cell is configured to force the through-flow to change direction such that elastic turbulence occurs, thereby enhancing mass transfer through the liquid and reducing overpotential at the electrodes, this enhances the uniformity of the deposited solids and inhibits parasitic reactions.

Description

Technical Field

[0001] This disclosure relates to a flow electrochemical cell (FEC) in which an electrochemical reaction results in the deposition of a solid phase at the electrodes. This electrochemical cell can be, for example, a rechargeable flow battery pack for storing energy. Background Technology

[0002] Flow electrochemical cells are used in a variety of equipment, including redox flow battery packs. In many battery pack types, two half-cells are separated by a membrane that prevents the liquids (often called electrolytes) of the two half-cells from mixing, but allows ions that need to pass from one half-cell to the other to pass through. During charging and discharging, in each half-cell, a liquid containing one or more substances undergoing an electrochemical reaction is pumped from an associated storage container through that half-cell, and after passing through that half-cell, is discharged to another storage container or recycled back to the container from which it originated.

[0003] Some flow electrochemical cells induce reactions in which a solute in the electrolyte is converted into a solid, which is then deposited from the solution at the electrodes. This can be the deposition of a metal at the negative electrode or the deposition of a metal compound such as an oxide or hydroxide at the positive electrode. The deposition of a metal or metal alloy solid phase in an electrochemical half-cell can be part of a process for extracting metals from ores (electrolytic extraction or electrolytic deposition) or a process for purifying metals by electrolysis (electrolytic refining). It can also be used in pre-enrichment techniques for trace analysis or as a process for removing metal ions from wastewater. If the deposition is reversible, the deposition and dissolution can be used for charging and discharging secondary battery packs. Electrochemical deposition and dissolution of metal oxides can also be used in secondary battery packs.

[0004] A flow electrochemical half-cell is an electrochemical reactor in which a liquid containing electroactive chemicals flows through or across electrode materials. At the electrodes, electrochemical reactions occur spontaneously or due to an externally applied potential that causes one or more electrons to transfer from the electrode to the electroactive chemical, or vice versa. When an electrochemical reaction in the half-cell causes a chemical to transform from a solute to a solid, the electroactive material in the solution must migrate to the electrode surface in a manner that allows electron transfer, and typically binds to or associates with that surface. The current at the electrodes depends on the rate at which the electroactive chemical migrates to or from the electrode surface.

[0005] Reactive substances are attracted toward the electrode by the potential at the electrode. The need to attract substances to the electrode results in what is called an overpotential, where the potential at the electrode is greater than the potential required to initiate the electrochemical reaction itself. The role of the overpotential is to enhance the transport of reactive substances to the surface, thereby increasing the current flow. This consumes a significant amount of electricity in mass transport within the liquid electrolyte, making the mass transport overpotential one of the biggest sources of inefficiency in electrochemical flow cells.

[0006] Overpotential can also promote unwanted chemical reactions, known as parasitic reactions, especially when the electrochemical reaction involves the deposition of solids at a surface. Generally, electrodeposition of metals and metal alloys occurs at the low potential of the negative electrode, and if water is used as the solvent in the electrolyte, the hydrogen evolution reaction (HER) is an unwanted parasitic reaction. Similarly, electrodeposition of metal oxides and mixed metal oxides occurs at the high potential of the positive electrode, and if water is used as the solvent, the oxygen evolution reaction (OER) is a parasitic reaction at the positive electrode.

[0007] Parasitic reactions are not only a waste of electricity, but if they lead to gas formation at the electrode, interfacial tension causes very small bubbles to adhere to the solid surface. The coalescence of adjacent bubbles then causes them to grow larger until they reach a point where their buoyancy overcomes the adhesion to the solid surface. When bubbles adhere to the solid surface, they mask an area of ​​that surface, preventing it from contacting the electrolyte and making it unusable for electrochemical reactions. This, in turn, affects the uniformity of deposition at the electrode.

[0008] For a given geometric electrode area (i.e., the area within the electrode profile), an electrode with a high specific surface area is desirable to maximize the rate at which the reaction can occur. However, for a constant geometric area, as the surface area of ​​the electrode increases, the permeability of the electrode generally decreases, resulting in a higher pressure drop across the electrode and requiring more energy for liquid circulation. A trade-off must be made between the conflicting requirements of high specific surface area and low pressure drop when the liquid flows through or across the electrode.

[0009] There is considerable work to be done in the fabrication of structured carbon electrodes for FEC. Commonly used high specific surface area materials include felts, cloths, and papers made of polymer (synthetic and natural) fibers. These structures are made into porous matrices with high specific surface areas by various methods, such as weaving, precipitation from solution, electrospinning, or otherwise, and then converted primarily to carbon through “carbonization,” in which most of the non-carbon elements (e.g., H, O, and N) present in organic materials are typically removed at high temperatures in a non-reactive atmosphere.

[0010] Designs using high specific surface area porous materials can be categorized into "flow-through" or "flow-through" types. In a "flow-through" type, there is an inlet to the porous material at one location and an outlet from the porous material at another location. In a "flow-through" type, the liquid flows over the outer surface of the porous material volume (which may be thin), and at least some of the liquid diffuses into the porous matrix. Flow-through designs can have the advantage of relatively low flow resistance, where the liquid is largely uniformly distributed when delivered to the porous electrode. However, this comes at the cost of relying on diffusion transport in the direction perpendicular to the channel and within the porous electrode to facilitate the movement of electroactive material from the channel to the electrode and from the electrode. Fully flow-through or flow-through electrodes represent extreme cases. Many flow field designs exist in between. Summary of the Invention

[0011] This summary is provided to introduce concepts that will be further set forth and described in the detailed description below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to help limit the scope of the claimed subject matter.

[0012] This disclosure utilizes the phenomenon of elastic turbulence, discovered in the late 20th century. It occurs at laminar flow velocities in Newtonian fluids such as pure water.

[0013] In a first aspect, this disclosure provides a system comprising:

[0014] An electrochemical half-cell includes an electrode and a liquid containing a dissolved reactive substance capable of undergoing an electrochemical reaction at the electrode, wherein the reaction converts the dissolved component into a solid deposited on the electrode; a structure defining a liquid flow path that carries the flow of the liquid to contact the electrode; and at least one pump for propelling the liquid along the flow path, wherein:

[0015] The liquid contains a solute that enables it to exhibit elastic turbulence, and

[0016] The flow path to or at the electrode is configured to force a change in the direction of liquid flow to induce elastic turbulence within the flow of the liquid in contact with the electrode.

[0017] The system can be a rechargeable battery pack system with a second half-cell comprising a second electrode and a liquid containing a second dissolved reactive substance capable of undergoing an electrochemical reaction at the second electrode; a structure defining a liquid flow path that carries the flow of the liquid to contact the second electrode; and at least one pump configured to propel the liquid along the flow path to contact the second electrode. The liquid may also contain a solute that enables the liquid to exhibit elastic turbulence, and the flow path to or at the second electrode may be configured to force a change in the direction of liquid flow to induce elastic turbulence within the flow of liquid in contact with the second electrode. The rechargeable battery pack system can also be a metal-air battery pack system with a second half-cell that converts water into oxygen during charging and reduces atmospheric oxygen back to water during discharging.

[0018] Another aspect of this disclosure provides a method for operating a flow electrochemical half-cell having an electrode in contact with a flow path of a liquid containing dissolved reactive substances capable of undergoing an electrochemical reaction at the electrode, thereby converting the dissolved reactive substances into a solid deposited on the electrode, wherein:

[0019] The liquid contains a solute that enables it to exhibit elastic turbulence.

[0020] The flow path in contact with the electrode forces a change in the direction of liquid flow, and

[0021] The method includes pumping the liquid along the flow path, wherein the liquid is in an elastic turbulent state when in contact with the electrode.

[0022] Elastic turbulence enhances the transport of reactive components of the liquid to the electrode and can also enhance the transport of generated substances from the electrode. This improvement in mass transport can increase the current density (current per unit area) at the electrode and / or reduce the overpotential required to transport reactive substances to the electrode surface at a specific rate. Enhanced transport can occur in two ways. Elastic turbulence can transport reactive substances to the electrode surface faster than through liquid diffusion and also carry reaction products away from the electrode surface. This is particularly relevant when the liquid is in an elastic turbulent state within a porous electrode. Secondly, in flow-through electrode designs, elastic turbulence in the channels adjacent to the porous electrode will increase the pressure drop along the channels, which will lead to more liquid entering the porous electrode.

[0023] In some embodiments of this disclosure, the half-cell is part of a flow battery pack. In other embodiments, the half-cell is used for electroplating. In still other embodiments, the half-cell can be used in processes for extracting or refining metals.

[0024] The flow path in contact with the electrode may include obstacles that force the liquid flow to change direction. In some embodiments of this disclosure, the flow guide provides an array of spaced obstacles that force the flow to change direction. In some embodiments, the flow through the electrode is formed by a porous mesh, and this mesh forces the liquid flow to repeatedly change direction. Attached Figure Description

[0025] Many of the figures are schematic and intended to show the components that are related to each other. Thin components, such as membranes, are shown with exaggerated thickness to make them and their locations easier to see.

[0026] Figure 1 This is a graph showing the experimental results of the onset of elastic turbulence.

[0027] Figure 2 This is a perspective view of the airflow guide.

[0028] Figure 3 This is an enlarged top view of a part of the flow guide.

[0029] Figure 4 This is a diagram of a device for observing elastic turbulence using birefringence.

[0030] Figure 5 The use of grayscale is shown Figure 4 Images obtained by the device.

[0031] Figure 6 yes Figure 4 The diagram shows a slightly enlarged cross-section of a flow chamber equipped with electrodes.

[0032] Figure 7A and Figure 7B It shows the use of Figure 4 and Figure 6 Images obtained by the device.

[0033] Figure 8 This is a schematic diagram showing the components of a flow battery pack.

[0034] Figure 9 It is along Figure 8 The view of the line CC.

[0035] Figure 10 This is a diagram showing the components of another flow battery pack.

[0036] Figure 11 This is a top view of a portion of the flow guide, showing the location of the hole passing through its base.

[0037] Figure 12 This is a schematic diagram showing the components of a metal-air flow battery pack.

[0038] Figure 13 This is a schematic diagram showing the components of another metal-air flow battery pack.

[0039] Figure 14 Three connected together are shown Figure 12 Flow battery pack.

[0040] Figure 15 It is along Figure 16 A schematic vertical cross-section of the electroplating bath of line EE.

[0041] Figure 16 It is along Figure 15 A schematic horizontal cross-section of line DD.

[0042] Figure 17 This is a top view of a part of another flow guide, showing columns with different cross-sections.

[0043] Figure 18 This is a schematic view of a device used to determine the operating parameters of an electrochemical half-cell.

[0044] Figure 19 and Figure 20 Experimental results obtained using an example of this device are shown. Detailed Implementation

[0045] This detailed description illustrates various embodiments of the present disclosure and the possibilities that can be used. It should be understood that, where practically feasible, the combined features or possibilities described may be used individually. Furthermore, the features or possibilities described in any embodiment may be used in any other embodiment, whenever possible.

[0046] This disclosure utilizes the phenomenon of elastic turbulence. It is well known that Newtonian fluids such as pure water can experience laminar or turbulent flow. This turbulence can be called inertial turbulence. The conditions for laminar and inertial turbulence are usually expressed by the Reynolds number, which is the ratio of inertial forces to viscous forces within the fluid. The Reynolds number is dimensionless because it is a ratio. Inertial turbulence exists at Reynolds numbers above approximately 2000. At Reynolds numbers below approximately 1500, the flow of Newtonian fluids is laminar. Flow paths within porous materials are typically small in size, and high velocities through such materials are impractical; consequently, it is impractical for flow to experience inertial turbulence through porous materials.

[0047] Elastic turbulence differs from inertial turbulence. It is a physical phenomenon discovered at the end of the twentieth century. It has been observed at low flow velocities, where the Reynolds number is low and Newtonian fluids will be in a laminar state. Some early observations of elastic turbulence used the older term "elastic instability." However, this term is more general and includes other forms of instability in flow. Literature related to elastic turbulence includes a detailed discussion by Steinberg in the Annual Review of Fluid Mechanics, Vol. 53, pp. 27–58 (2021).

[0048] The elastic turbulence phenomenon of liquids requires:

[0049] (i) Solutes that possess elastic properties, thereby enabling liquid solutions to exhibit elastic turbulence.

[0050] (ii) Liquid flow paths that force a continuous change in the direction of liquid flow, and

[0051] (iii) Pump the liquid along the flow path at a sufficient speed.

[0052] A continuous change of direction can be a continuous curve (as in concentric or spiral flow), or it can alternate between turning right and turning left.

[0053] Elastic turbulence occurs in solutions containing solutes with flexible structures. One class of materials capable of elastic deformation, allowing the solution to exhibit elastic turbulence, is polymers containing long, flexible, linear chains. The number of monomer units in the polymer can be at least 5,000, and can be significantly more, such as at least 25,000. Monomer units can exist as linear chains of at least 1,000 monomer units, each linked to the next monomer unit by a single covalent bond, allowing a monomer unit to rotate relative to its adjacent monomer unit. The individual linear chains can be longer, and the polymer can contain at least 5,000 or even at least 10,000 linear monomer units. The polymer chain can contain only one monomer, or the chain can be a copolymer of more than one monomer, such as a linear block copolymer. The polymer can also include long chain side chains attached to monomer units, which are linked together by a single covalent bond. If the chain contains units that are themselves oligomers, such as in block copolymers, the oligomer units can rotate more freely relative to each other than the monomer residues within the oligomer unit. The polymer may include some chain branching, for example, at branch points where three or more straight chains (each with at least 1000 monomer units) are linked together. When using long-chain polymers to enable elastic turbulence, it is desirable to include biocides to protect the long-chain linear polymers from biodegradation.

[0054] The flexibility of polymer chains allows polymer molecules to become entangled. This flexibility can be described using mathematical models. The free-jointing chain model is commonly used, and the flexibility of a particular polymer can be indicated by the parameters of an equivalent free-jointing chain (which is itself a mathematical model). This approach is described in Chapter 2 of Rubinstein and Colby's "Polymer Physics" (Oxford University Press, 2003). Equivalent free-jointing chains have the same mean-square end-to-end distance and the same maximum end-to-end distance as the actual polymer, but are considered to be composed of so-called Kuhn monomers, which are capable of rotating freely relative to each other. These model monomers have a length and molar mass called the Kuhn length.

[0055] The polymer used to achieve elastic turbulence may contain at least one flexible polymer chain whose length and composition are represented by at least 5,000 Kuhn monomers having a Kuhn length of no more than 100 angstroms (10 nm) and possibly no more than 50 angstroms. If the polymer is a single unbranched chain, its length and composition may correspond to at least 20,000 Kuhn monomers, and possibly at least 50,000 Kuhn monomers.

[0056] The average molecular weight of the polymer can be at least one megadalton, that is, at least 10. 6 The concentration of such long-chain / high molecular weight polymers in the solution, which enable elastic turbulence to occur, can be less than 5% by weight, for example, in the range of 0.05% or 0.1% by weight up to 1% or 2% by weight.

[0057] Elastic turbulence has been observed in solutions of several different long-chain polymers. One such polymer is polyacrylamide, which can be hydrolyzed or partially hydrolyzed. Groisman and Steinberg presented experimental evidence for elastic turbulence in solutions of high molecular weight polyacrylamide in "Elastic Turbulence in a polymer solution flow" Nature, Vol. 45, p. 53 (2000). Other examples of long-chain polymers that generate elastic turbulence reportedly include: polyisobutylene with a molecular weight of 4 to 6 megadaltons dissolved in organic solvents (Dris and Shaqfeh, J. Non-Newtonian Fluid Mech. Vol. 80, pp. 1–58 (1998)); polystyrene with a molecular weight of 18 megadaltons in organic solutions (Magda and Larson, J. Non-Newtonian Fluid Mech. Vol. 30, pp. 1–19 (1988)); and polyethylene oxide with a molecular weight of 4 megadaltons in aqueous solutions (Davoodi et al., J. Liquid Mech. Vol. 857, pp. 823–850 (2018)). Kuhn lengths of 18 Å and 11 Å are given by Rubinstein and Colby, p. 53. According to reports, the Kuhn length for polyacrylamide is 15 to 25 angstroms (Fetters, Lohse, and Colby, "Chain Dimensions and Entanglement Spacings" in Physical Properties of Polymers Handbook; edited by Mark, JE; Springer: New York, 2007; pp. 447–454).

[0058] Long-chain partially hydrolyzed polyacrylamide linear polymers with molecular weights exceeding 1 megadaltons are available from SNF Floerger, headquartered in Andrézieux, France.

[0059] Another class of materials capable of elastic deformation and enabling solutions to exhibit elastic turbulence are viscoelastic surfactants, which form worm-like micelles in solution. A large body of scientific literature addresses surfactants that form worm-like micelles, their properties, and applications. One review is Yang's "Viscoelastic wormlike micelles and their applications," Current Opinion in Colloid & Interface Science, Vol. 7, pp. 276–281 (2002). Discussions of properties include Raghavan and Kaler's "Highly Viscoelastic Wormlike Micellar Solutions Formed by Cationic Surfactants with Long Unsaturated Tails," Langmuir, Vol. 17, pp. 300–306 (2001) and Beaumont et al.'s "Turbulent flows in highly elastic wormlike micelles," SoftMatter, Vol. 9, p. 735 (2013). Fardin et al.’s “Elastic Turbulence in ShearBanding Wormlike Micelles”, Physical Review Letters, Vol. 104, 178303 (2010) mentions an example of using hexadecyltrimethyl bromide as a surfactant.

[0060] When a solution contains substances capable of inducing elastic turbulence, elastic turbulence occurs if the solution is flowing at a sufficient velocity (which can be low) and the flow path causes the streamlines of the flow to bend. Therefore, one known possibility for a flow path that induces elastic turbulence is a serpentine channel. Another possibility is a flow path with obstructions that force the streamlines of the flow to change direction. Such obstructions can be manufactured and arranged in a pattern to force the flow around the obstruction to change direction.

[0061] Porous materials can also provide flow paths that cause a series of directional changes. Changes in the orientation of the pores and the connections between them can force a change in flow direction. Porous materials can be fibrous, and the openings between the fibers will provide flow paths with a series of directional changes.

[0062] The ability of fluid compositions to exhibit elastic turbulence can be experimentally demonstrated using a laboratory rheometer. In a cone-plate rheometer unit, the onset of elastic instability with increasing shear is observed as a significant increase in viscosity at a given shear rate, which is associated with a sudden increase in noise in the measured torque signal. This has been described by DOOlagunju, Z Angew MathPhys, 46(1995)224-238, “Instabilities and bifurcations of von Karmansimilarity solutions in swirling viscoelastic flow”, and also by E. Tran and A. Clarke, “The relaxation time of entangled HPAM solutions in flow”, Journal of Non-Newtonian Fluid Mechanics, 311(2023)104954. The significant increase in viscosity can be viewed as a change in the slope (sometimes referred to as a micro-increase) in the viscosity versus shear rate plot.

[0063] Figure 1 The results of experimental tests performed using a laboratory rheometer, operated to measure at the increasing shear rate step and subsequently at the decreasing shear rate step, are shown. It is a graph of the dynamic viscosity versus increasing shear rate for three aqueous solutions containing 0.456 wt% sodium chloride, a small percentage of polymer, and a few drops of a biocide composed of isopropanol and thiourea. In one of these aqueous solutions ( Figure 1 The first solution (shown as a white circle) contains 0.24 wt% Flopaam 3630 from SNF Floerger, a linear polyacrylamide with an average molecular weight of 18 to 20 megadaltons. The second solution (shown as a circle with a cross) contains 0.24 wt% xanthan gum. The third solution (shown as a solid circle) contains 0.12 wt% Flopaam 3060 and 0.12 wt% xanthan gum, a 1:1 mixture. Solutions containing polyacrylamide alone or mixed with xanthan gum show a time of approximately 150 seconds. -1 The slope change of the plotted curve is observed here. This indicates that elastic turbulence begins as the shear rate increases. Solutions containing xanthan gum do not exhibit this slope change, indicating that this more rigid polymer does not enable elastic turbulence to occur.

[0064] Similar experiments used a solution containing 0.2 wt% Flopaam 6040 (also from SNF Floerger), with an average molecular weight between 25 and 30 megadaltons. Here, the onset of elastic turbulence with increasing shear rate is also considered to occur at approximately 150 s. -1 The change in slope of the curve plotted at a certain point indicates the onset of elastic turbulence. (The shear rate at which elastic turbulence begins in an electrochemical half-cell may be low.)

[0065] Figures 2 to 6 Experimental demonstrations of elastic turbulence in aqueous solutions of viscoelastic surfactants and flexible polymers.

[0066] Figure 2 The guide 10 used in these experiments is shown. It has a regularly spaced array of columns 12 with a square cross-section integral with the base 13. The two edges of the array are completed by columns 14 with a triangular cross-section. Figure 3 This is an enlarged top view of a portion of the flow guide. As shown, each of the pillars 12 has a square cross-section, where flat surfaces 16 meet at corner edges 17 and 18. The width of the flat surfaces 16 is... Figure 3 The middle is indicated as "a", and the distance between the faces 16 of adjacent pillars is indicated as "b". The width of the gap between the edges 18 of the two faces is given by the Pythagorean theorem as μ(2b). 2 Each column 12 is positioned such that the diagonal of the square cross-section spanning the corner edges 17 is aligned with the overall direction of flow. As indicated by the dashed lines, the liquid flows through the gap between the facing edges 18 of adjacent columns 12, but is subsequently forced downstream by the columns. Thus, the array of columns 34 impedes the straight-through flow of the liquid, causing the flow streamlines to repeatedly change direction.

[0067] The flow guide 10 is made of a transparent polymer and is located within the chamber 20, which is in Figure 4 The image is shown in cross-section. Chamber 20 is formed by two transparent polymer blocks 21 and 22, which are held together by bolts (not shown). A flow guide 10 is located in the cavity between the two blocks. A liquid inlet 23 and a liquid outlet 24 are present, leading to the cavity. When liquid is pumped through chamber 20, the liquid... Figure 2 The fluid enters the guide 10 at the end indicated as 15 and then flows through the gap between the columns 12. If the liquid contains substances capable of exhibiting elastic turbulence and the flow velocity is sufficient, repeated changes in direction can induce elastic turbulence.

[0068] The occurrence of elastic turbulence is observed using techniques that utilize the birefringence phenomenon. The apparatus includes... Figure 4As shown, it shares some similarities with the device described by Moss GR and Rothstein JP in “Flow of worm-like micelle solutions through a periodic array of cylinders”, Journal of Non-Newtonian Fluid Mechanics, Vol. 165, pp. 1-13, 2410.

[0069] The light beams from the red LED 25R and the green LED 25G are guided toward the camera 26 along paths shown as solid lines and dashed lines, respectively. The cavity 20 is positioned between linear polarization filters 28R and 29R, whose polarization directions are set at right angles (i.e., intersecting), and between linear polarization filters 28G and 29G, whose polarization directions are also set at right angles to each other. Therefore, no light can reach the camera 26 unless birefringence within the cavity changes the polarization angle of the light as it passes through the cavity 20. Filters 28R and 28G are set so that the polarization planes of the red and green light entering the cavity 16 are at right angles to each other. A dichroic mirror 30, which passes through the red beam and reflects the green beam, is used to merge the red and green beams, then separate them after they have passed through the cavity 20, and subsequently recombine them before they reach the camera 26.

[0070] The other components of the device are a reflector 38, a lens 32, red and green bandpass filters 34G and 34R, and a dichroic mirror 36, which are set with a 90° rotation difference relative to the path of the red beam to eliminate polarization rotation induced by Fresnel refraction. The green beam does not require such a dichroic mirror because its polarization does not induce polarization rotation.

[0071] The worm-like micelles formed by the viscoelastic surfactant are birefringent. Therefore, when these molecules become aligned by the liquid flow within chamber 20 and are irradiated with polarized red and green light, they can alter the plane of polarization of the light, allowing some of the light to pass through filters 29R and 29G to reach the camera—something that wouldn't happen if the micelles were aligned with the plane of polarization of the light. Providing these two beams with different planes of polarization solves this problem: if the micelles happen to be aligned with the red polarization, they will not be aligned with the green polarization, and vice versa. Therefore, the device is sensitive to polarization alignment in either direction.

[0072] As the liquid containing worm-like micelles flows through the chamber, these micelles become aligned by stretching the flow as the liquid flows around the columns 12, 14 of the guide 10, and the birefringence from the aligned micelles can be perceived as red or green in the pictures or videos recorded by the camera 26.

[0073] The first experiment was conducted using a solution similar to the one mentioned by Moss and Rothstein in the aforementioned paper. This solution contained 100 mM (approximately 4 wt%) of the viscoelastic cationic surfactant hexadecylpyridinium chloride and 50 mM (approximately 0.8 wt%) of sodium salicylate, dissolved in 100 mM (approximately 0.6 wt%) of sodium chloride brine in distilled water.

[0074] A viscoelastic solution is pumped through chamber 20 at a low flow rate of 5 ml per minute. Camera 26 records video for a period of 5 seconds at a rate of 20 frames per second, and the recording shows that the flow pattern around the column of the guide remains constant. Four images from this video recording, spaced at half-second intervals, are shown in grayscale. Figure 5 The top row shows that the change from one image to the next is negligible. The initial color images show red lines extending in the flow direction from the downstream corner of each column. In one image, white outlines have been drawn around one of these white outlines indicated as 40. These red lines maintain the same intensity and location throughout the video recording. The flow rate was then increased to 25 ml / min, and the video was recorded again for 5 seconds. This video recording at a flow rate of 25 ml / min is very different from the video recording at a flow rate of 5 ml / min. It shows constant movement. The color patches (which are where the stretching flow aligns the micelles) constantly move from one location to another and change intensity. Four images from the video with a flow rate of 25 ml / min are reproduced in grayscale, as shown below. Figure 5 The bottom row shows multiple changes from one image to the next. For example, arrow 41 points to a red patch that is present in one image but not in the previous one, and diminishes in the two subsequent images. At position 42, a red area is present that is not present in the previous image and diminishes again in the next two images. The second image in the bottom row also shows a strong green area 43 that is not present in the first image and largely disappears in the third image. Therefore, it can be seen that the flow at 5 ml / min is laminar, but at 25 ml / min, the flow has become turbulent.

[0075] Similar experiments were conducted using a solution containing partially hydrolyzed polyacrylamide (HPAM) with an average molecular weight of 18 MDa, which exhibited elastic turbulence, and xanthan gum as an additional thickener, as well as a comparative solution containing only xanthan gum (as mentioned above, which is too stiff to induce elastic turbulence). These polymers did not form micelles, but did induce birefringence when aligned. The flow rates and observations are presented in the table below, which also includes commentary from the above experiments using viscoelastic surfactants.

[0076]

[0077] These comments clearly show that solutions containing HPAM and xanthan gum exhibit elastic turbulence at 15 ml·s and above, but solutions containing xanthan gum but not HPAM do not exhibit elastic turbulence even at 30 ml·min.

[0078] Elastic turbulence is an instability in flow that causes pressure fluctuations within the liquid. We have now discovered that such pressure fluctuations can separate bubbles from the surface before they grow to a size where buoyancy overcomes the forces holding them on the surface, thus increasing the area of ​​the electrode surface available for the reaction. Further experiments have confirmed this. Figure 6 As shown, chamber 20 has a platinum wire electrode 45 and a small copper block 46 serving as a second electrode on the surface of the upper block 21. The platinum wire electrode protrudes into the space between the two pillars of the guide member. The electrical connection to block 46 is indicated at 47. A power supply of approximately 2 volts is connected to the electrodes, with copper block 46 as the positive terminal and wire 45 as the negative terminal.

[0079] A solution containing 0.12 wt% HPAM with an average molecular weight of 18 MDa, 0.12 wt% xanthan gum, and 0.456 wt% sodium chloride is pumped through guide 10 and uses, for example... Figure 4 The apparatus shown is used to observe the flow. When the power is turned on, in... Figure 6 Bubbles are seen in the flow downstream of the platinum wire electrode 45 shown. Bubbles are visible in the flow because they refract light out of its path, and therefore appear dark.

[0080] Figure 7A The image shows the flow rate at 5 ml / min without elastic turbulence. Figure 7B This is a flow image at a flow rate of 45 ml / min where elastic turbulence exists. The image has been processed to show bubbles in contrast to the rest of the image, and squares have been drawn to more clearly show the edges of some columns.

[0081] The bubble diameter was visually estimated by comparing it with the dimensions across column 12 and between columns. When the flow rate was 5 ml / min (too low to induce elastic turbulence), the bubble diameter was in the range of approximately 0.2 mm to 0.5 mm. However, when the flow rate was increased to 45 ml / min where elastic turbulence was present, the bubbles were significantly smaller and the diameter was in the range of approximately 0.03 mm to 0.2 mm. This indicates that the elastic turbulence removed the bubble from the platinum wire electrode 45 before it grew to a size that would have been necessary for the bubble to leave the electrode without elastic turbulence.

[0082] The flow battery packs according to this disclosure can use a wide range of electrochemistry, including possibilities already described in the published literature (but without mention of additives capable of achieving elastic turbulence). For the electrochemistry in which metals are deposited at the negative electrode of the battery, nickel, iron, zinc, and tin have all been named in publications. Zinc is often chosen because it is readily available in large quantities at a moderate cost.

[0083] Figure 6 Figure 7 illustrates a rechargeable flow battery pack, in which the reaction in one half-cell is the deposition and dissolution of metal. The pack has a housing 50 within which half-cells are located on either side of a separator 52. The half-cell to the left of the membrane 52 contains the negative electrode 54 of the pack. This is a flow electrode composed of a metal mesh, the metal of which undergoes deposition and dissolution during charging and discharging. The half-cell shown to the right of the membrane 52 contains a flow guide 56 having an array of spaced-apart pillars 58 with a square cross-section, the pillars being aligned with… Figure 2 It is integrated with the base 59 in the same manner as shown. However, as Figure 9 As shown in the cross-section, the current guide 56 provides a large array of pillars 58. The current guide 56 is formed of graphite, which is conductive. This current guide 56 provides the positive electrode of the battery pack. Electrical connections to electrodes 54 and 56 are indicated at 60.

[0084] Each half-cell has an inlet 62 and an outlet 64. These half-cells are connected to a pump 67 via a pipe 66, which is connected to liquid electrolyte tanks 68a and 68b. Pump 67 is used to circulate liquid from tanks 68a and 68b through the half-cells and back to the same tank. Pressure sensors 69 are installed near each inlet and outlet.

[0085] According to this disclosure, the liquid flowing through each half-cell in the half-cell contains a solute that enables the liquid to exhibit elastic turbulence. The solute can be a high molecular weight linear polymer capable of elastic deformation, or it can be a viscoelastic surfactant capable of forming worm-like micelles in solution. If the solute is a polymer, the liquid may contain a small amount of biocide to prevent the biodegradation of the polymer. The pumping power is selected such that the flow in the conduit and the flow reaching the inlet ends of electrodes 54 and 56 is laminar, but when the liquid from tank 68a is pumped through electrode 54, the metal mesh forming electrode 54 causes the streamlines of the flow to change direction multiple times, thereby generating elastic turbulence within the electrode. This enhances the mass transport of metal ions to and from the electrode surface. This produces a more uniform deposition on the electrode and reduces dendrite formation. It also reduces the overpotential during charging, which reduces parasitic hydrogen evolution reactions.

[0086] Similarly, as liquid from tank 68b is pumped through the half-cell to the right side of membrane 52, column 58 forces the streamlines of the flow to repeatedly change direction, as... Figure 3 As indicated by the dashed line. This creates an elastic turbulent state within the liquid as it flows through the guide 56, which serves as the positive electrode of the battery, and enhances the transport of reactants to and from the electrode surface, thereby reducing the overpotential.

[0087] Example 1

[0088] As an example, the battery pack can be a zinc-bromine battery pack. The liquid electrolyte of the left half-cell is an aqueous solution of zinc chloride containing the polymer or viscoelastic surfactant mentioned above. When the battery pack is charged, zinc metal is deposited on the mesh 54, and during discharge, zinc from the mesh dissolves as zinc ions in the flowing liquid. Therefore, the reaction at the negative electrode is...

[0089] Zn Zn 2+ +2e -

[0090] The elastic turbulence within the mesh electrode 54 enhances the mass transport of zinc ions to and from the electrode surface. This results in more uniform zinc deposition on the electrode during charging and reduces zinc dendrite formation. It also lowers the overpotential during charging, which reduces the parasitic hydrogen evolution reaction.

[0091] In this embodiment, the liquid electrolyte of the half-cell on the right side of the membrane is hydrobromic acid, which contains the aforementioned high molecular weight flexible polymer or viscoelastic surfactant. A quaternary ammonium bromide is mixed with the electrolyte in tank 68b. Without this quaternary ammonium compound, the reaction at the positive electrode 56 would be the conversion of bromide ions to free bromine, and vice versa. Flow batteries in which zinc bromide is reversibly converted to zinc metal and bromine are known, and the present invention can be implemented using such a system, collecting free bromine at the bottom of tank 68b. However, providing a quaternary ammonium compound in the electrolyte allows bromine to form Br3, where the cation is Br3. - The quaternary ammonium salts reduce the amount of toxic free bromine in the system. These quaternary ammonium salts have low solubility in water and accumulate at the bottom of tank 68b in either liquid or solid form. In "Systematic Study of Quaternary Ammonium Reactions for Bromine Sequestering Application in High Energy Density Electrolytes for Hydrogen Bromine Redox Flow Batteries," Molecules, Vol. 26, p. 2721 (2021), many quaternary ammonium compounds for this purpose are discussed. The reaction in the half-cell is:

[0092] At the electrodes;

[0093] In solution;

[0094] Q represents multiple organic groups that together form four covalent bonds with nitrogen.

[0095] To prevent the mixing of liquid electrolytes in the half-cell and self-discharge due to the recombination of bromine and zinc, the separator membrane 52 is an ion exchange membrane that allows hydrogen ions to pass through but ideally prevents other dissolved substances from passing through.

[0096] like Figure 8 The redox flow battery pack shown can be implemented with other metals at the negative electrode and with other redox systems at the positive electrode. Examples 2, 3, and 4 below illustrate applications such as... Figure 8Other electrochemistry in the illustrated flow battery pack. In all these embodiments, the liquid pumped through the two half-cells contains a high molecular weight flexible polymer or viscoelastic surfactant, enabling it to exhibit elastic turbulence. During operation, whether charging or discharging the battery pack, the liquid is pumped through the half-cells at a certain rate, resulting in laminar flow in tank 68 and conduit 66, but elastic turbulence occurs as the liquid passes through electrode 54 and guide 56. Elastic turbulence enhances transport to and from the electrodes, reducing overpotential. During charging, this leads to more uniform metal deposition and a reduced overpotential, which reduces parasitic reactions.

[0097] Example 2

[0098] This embodiment utilizes cerium salts in its electrochemical process. For example... Figure 8 The liquid electrolyte in the left half-cell of the device is an aqueous solution of zinc in the form of methanesulfonate or sulfate. The liquid in the right half-cell is a solution of cerium methanesulfonate. During charging, zinc metal is deposited on the mesh electrode 54, and cerium salts in the solution of the right half-cell are released from Ce. 4+ Converted to Ce 3+ During discharge, zinc ions dissolve from the positive electrode, and cerium ions are removed from Ce. 3+ Converted to Ce 4+ Membrane 52 is an ion exchange membrane that allows hydrogen ions to pass through. The reaction can be written as:

[0099]

[0100] Leung et al. described the use of cerium salts in half-cells in “Characterization of a zinc-cerium flow battery”, Journal of Power Sources, Vol. 196, p. 5174 (2011).

[0101] Example 3

[0102] like Figure 8 Another possibility for the flow battery pack shown is to utilize an alkaline liquid and a ferrocyanide / ferrocyanide couple. Mahmood et al. describe a system using these materials in “A Newly Designed Fixed Bed RedoxFlow Battery Based on Zinc / Nickel System” J Electrochem. Soc. Sci., Vol. 8(3), pp. 236-243 (2017).

[0103] The liquid in the left half of the battery is a sodium hydroxide solution. Figure 8The liquid in the half-cell on the right side of the device is a sodium hydroxide solution containing potassium ferrocyanide and / or potassium ferricyanide. During discharge, zinc from the mesh electrode 54 dissolves into sodium zincate, and ferricyanide is converted to ferrocyanide at the graphite electrode 56. During charging, zinc is deposited on the mesh electrode 54, and ferrocyanide ions are converted to ferricyanide at the graphite electrode 56. The reaction can be written as follows:

[0104]

[0105] Example 4

[0106] This embodiment uses iron as the metal, which has the electrochemical reactions described by Huska and Savinell in "Investigation of factors affecting performance of the iron-redox battery" J. Electrochem. Soc. Soc. Vol. 128, p. 18 (1981). Figure 8 The liquid in the left half-cell of the device is a ferrous chloride solution containing ammonium chloride to increase conductivity, and electrode 54 is an iron wire mesh. The liquid in the right half-cell is a mixture of ferrous chloride and ferric chloride containing ammonium chloride, and electrode 56 is graphite. During charging, iron metal is deposited on the negative electrode 54, while ferrous ions are converted into ferric ions in the right half-cell. A reverse reaction occurs during discharging.

[0107] In the attached diagram Figure 10 This illustrates a flow battery pack with a slightly different construction. (Compared to...) Figure 8 Identical components are shown using the same reference numerals. In the two half-cells, electrode 70 is a porous carbon felt. Flow guides 72 are positioned between the separator membrane 52 and electrode 70. These flow guides are similar to... Figure 8 The flow guides shown can be made of non-conductive plastic material. They are positioned such that their posts 58 extend toward the electrodes, and the base of each flow guide has, for example, [details omitted]. Figure 11 The through-hole 74 shown allows ions passing through the separator to travel from one half-cell to the other. The liquid solution contains a high molecular weight flexible polymer or viscoelastic surfactant and is pumped at a certain rate, such that the flow through the tank and pipes is laminar, but elastic turbulence occurs during the flow through the guide. The flow within the carbon felt will be in an elastic turbulent state for two reasons: this is because the fibers of the felt will force the flow to repeatedly change direction, and also because the elastic turbulence will continue to penetrate a certain distance into the felt as the liquid in an elastic turbulent state flows into the carbon felt from the guide.

[0108] Example 5

[0109] As an example, such as Figure 10 The flow battery pack shown is used in conjunction with the material combination proposed by Zhou et al. in “A Sn-Fe flowbattery with excellent rate and cycle performance” J. Power Sources, Vol. 404, p. 89 (2018).

[0110] The liquid in the left-hand half-cell is a solution of stannous chloride in hydrochloric acid. Tin is deposited on electrode 54 during charging and dissolves from the electrode during discharging. In the right-hand half-cell, the liquid is a mixture of ferrous chloride and ferric chloride in hydrochloric acid.

[0111] Example 6

[0112] As another example, Figure 10 The battery pack was used in conjunction with a system in which solid-phase deposition occurred in both half-cells. Xie et al. disclosed the electrochemistry in “A highly reversible neutral zinc / manganese battery for stationary energy storage”, Energy and Electrochemistry, Vol. 13, p. 135 (2020). The same liquid electrolyte was used in both half-cells. It contained zinc acetate and manganese acetate, as well as potassium chloride to increase the concentration of ions in the solution. During charging, zinc metal was deposited on the carbon felt forming the negative electrode in the left-handed half-cell, and manganese dioxide was deposited on the carbon felt electrode in the right-handed half-cell. Xie et al. gave the reaction of manganese acetate as follows:

[0113]

[0114] Example 7

[0115] This example also uses Figure 10 The battery pack layout is as follows. It uses the electrochemistry published by Hazza et al. in "A novel flow battery: Alead acid battery based on an electrolyte with soluble lead (II). Part I. Preliminary studies" Phys. Chem. Chem. Phys. Vol. 6, p. 1773 (2004). Solid deposits are present in both half-cells. The electrolyte in both half-cells is a solution of lead in methanesulfonic acid. During charging of the battery pack, lead is deposited on the negative electrode, and lead oxide is deposited on the positive electrode. The reaction is...

[0116] At the negative electrode

[0117] At the positive pole

[0118] and overall

[0119]

[0120] Example 8

[0121] Figure 10 The battery pack layout can also be used in primary cells where zinc and copper are deposited at the negative and positive electrodes, respectively. Figure 10 The left half-cell with the negative electrode uses a zinc sulfate solution as the electrolyte. Zinc is deposited on the electrode during charging and dissolves during discharging. The right half-cell with the positive electrode uses a copper sulfate solution as the electrolyte. Copper is deposited on the positive electrode during discharging and dissolves from it during charging.

[0122] Figure 12 A rechargeable metal-air flow battery pack is shown. It has two half-cells inside the casing, and these half-cells are separated by a membrane 52. The left half-cell is similar to... Figure 10 The left-hand half-cell is shown. It contains a negative electrode 70, which is a porous carbon felt, and also contains a current guide 72 between the electrode and the separator. This current guide can be connected to... Figure 10 The flow guide 72 used in the battery pack shown is the same. Pump 67 is used to circulate the electrolyte containing a high molecular weight flexible polymer or viscoelastic surfactant from tank 68a at a certain flow rate, such that the flow in tank 68a and pipe 66 is laminar, but the flow through conduit 72 and through the porous carbon electrode 70 is elastically turbulent. Pressure sensor 69 is positioned near the inlet and outlet of the half-cell. The electrolyte of the half-cell is an aqueous solution containing metal ions.

[0123] During charging, the metal is deposited on the carbon electrode, and during discharging, the metal is redissolved in the flowing liquid. The metal can be zinc, but other metals can also be used. Separator 52 is an ion exchange membrane that allows hydrogen ions to pass through but prevents metal ions from entering the right-hand half-cell.

[0124] The right-hand half-cell converts water into oxygen and hydrogen ions during charging and obtains oxygen from the atmosphere during discharging. It has a section containing a liquid electrolyte and a gas section without liquid that is open to the atmosphere. The section containing the electrolyte has a guide 72 adjacent to the separator 52. This guide can be the same as the guide in the left-hand half-cell and (as already mentioned) with... Figure 10The current guide is the same as that in the flow battery pack. Adjacent to the current guide is a porous catalyst layer 76, which may be a carbon felt impregnated with one or two reactive catalysts. This catalyst layer 76 is in contact with a current carrier 78, which may be a mesh made of titanium or other metals that do not react in the system.

[0125] The gas section of the half-cell extends from the current carrier 78 to the housing 50. A porous layer 80 of hydrophobic material abuts against the current carrier 78. This layer 80 is referred to as the gas transport layer. Because it is hydrophobic, it prevents aqueous liquids from flowing into the gas section of the half-cell.

[0126] The liquid in the right-hand half-cell is a neutral or acidic aqueous solution containing a flexible high molecular weight polymer or a viscoelastic surfactant. It is drawn from the supply tank 82 and guided upwards through the guide tube 72 by the pump 84. It then flows through the gas / liquid separator 86 to allow any entrained gas to escape and return from there to the supply tank 82. The flow rate makes the flow in the conduit 88 laminar, but induces elastic turbulence within the guide tube and possibly within the catalyst layer 76, whose fibrous material forces the flow to repeatedly change direction.

[0127] During charging, the electrochemical reaction in the right-hand half-cell is the oxygen evolution reaction (OER), and a catalyst is provided in the catalyst layer for this reaction. Oxygen formed in this reaction can enter through the current collector grid 78 and pass through the gas transport layer 80, and is then released into the atmosphere. Some oxygen can enter the liquid stream from the catalyst layer and be released into the atmosphere at the separator 86.

[0128] During discharge, fan 90 provides airflow through the gas section of the right-hand half-cell, and atmospheric oxygen diffuses through gas transport layer 80 and mesh 78 to catalyst layer 76, where it undergoes the oxygen reduction reaction (ORR). Catalyst layer 76 may contain compounds that act as catalysts for both the OER and ORR reactions, or it may contain a mixture of two catalysts, one for the OER and one for the ORR. Nazir et al. discuss catalysts for the OER and ORR reactions, or both, in A Review of Rechargeable Zinc-Air Batteries: Recent Progress and Future Perspectives, Nano-Micro Letters, Vol. 16, p. 138.

[0129] Figure 13Different configurations of the metal-air battery pack are shown, each with a separate half-cell for the OER and ORR reactions. This avoids contact between the circulating liquid and the ORR catalyst during charging, and correspondingly avoids contact between the circulating liquid and the OER catalyst during discharging of the battery pack.

[0130] The negative electrode is a porous metal mesh 92 between two separator membranes 52 (although a porous carbon electrode may be used). During charging and discharging, electrolyte from tank 68a is circulated through this electrode by pump 67. This liquid contains a flexible high molecular weight polymer or viscoelastic surfactant to provide elastic turbulence as it flows through the mesh electrode.

[0131] The half-cell on the right side of the central mesh electrode is used during charging, and the half-cell on the left side is used during battery discharge. Both half-cells have a current guide 72, a catalyst layer 76a or 76b, a current collector mesh 78a or 78b, and a gas transport layer 80a or 80b, as shown. Figure 12 As shown. Catalyst layer 76a is impregnated with ORR catalyst, and catalyst layer 76b is impregnated with OER catalyst. During charging, pump 94 is used to circulate liquid from tank 82 through the right-hand half-cell, while fan 90 and pump 95 are off and electrical connection 60a is not connected to the power source. During battery discharge, pump 96 is used to circulate liquid through the left-hand half-cell, while pump 94 is off, and fan 90 is used to blow air onto and into gas transport layer 80a.

[0132] To simplify the explanation, Figures 8 to 12 This illustrates a single electrochemical cell consisting of two half-cells. The common practice is to assemble multiple electrochemical cells together. This is achieved by… Figure 14 For example, it shows side-by-side arrangements Figure 12 Three metal-air batteries. In this embodiment, a half-cell in which metal is deposited at the electrodes and dissolves from the electrodes is supplied with liquid electrolyte from a single tank 68 via a single pump 67. Liquid from the half-cell that forms oxygen during charging is carried to a single gas / liquid separator 86. A single fan 90 supplies air to these half-cells during discharging. The current carriers in the oxygen-producing half-cell can be electrically connected, and the negative electrodes in the hydrogen-producing half-cell can be similarly electrically connected together, such that the batteries are connected in parallel. However, series connection of the batteries is also possible.

[0133] In the various flow battery implementations described above, the electrolytes in both half-cells contain a solute, which is either a flexible high-molecular-weight polymer or a surfactant that forms worm-like micelles, and in either case, elastic turbulence can occur. However, elastic turbulence may be used in one half-cell where solids are deposited at the electrodes, but not in the other half-cell.

[0134] Figure 12 and Figure 13 The use of elastic turbulence in an electroplating process is illustrated. As shown in cross-section, the process is carried out in an electroplating bath 102 containing an aqueous electrolyte, with the surface at 104. Immersed in the liquid and resting on a support 106, the workpiece 108, the upper surface of which will be electroplated, is also shown. An electrical connection 110 leads to the immersed positive electrode 112 and the workpiece 108.

[0135] The flow guide 114 is used to provide elastic turbulence at the upper surface of the workpiece 108. The flow guide 114 has a square cross-section column 116 extending from the base 118, similar to... Figure 2 The guide member shown is positioned above the workpiece 108, with its column 116 extending downward toward the workpiece 108, but with a small gap between the end of the column and the workpiece. The guide member 114 rests on supports 120, 121 at the end of the electroplating bath. Figure 15 The horizontal cross-section shows the side edge of the flow guide adjacent to the side surface 122 of the electroplating bath. This horizontal cross-section also shows the rectangular outline 124 of the workpiece 108 below the flow guide. It can be seen that the flow guide 114 extends beyond the side and end edges of the workpiece.

[0136] Pump 130 draws electrolyte from the lower part of the bath through pipe 132 and directs it into a horizontal distribution manifold 136 through pipe 134. Above the manifold, plate 128 extends from one end of the bath to one end of a flow guide. The walls of the bath, together with support 121 and plate 128, force the flow from manifold 136 into and through flow guide 114, where the column 116 of flow guide causes repeated changes in direction, thus making the flowing liquid exhibit elastic turbulence. This elastic turbulence continues into the short gap between flow guide 114 and the top surface 108 of the workpiece, and thus enhances the transport of metal ions to the top surface of the workpiece, thereby producing uniform metal deposition on the workpiece and mitigating overvoltage and parasitic reactions. The elastic turbulence extends over the entire area of ​​the top surface of the workpiece because the flow guide extends beyond the side and end edges of the workpiece.

[0137] In the aforementioned flow battery pack and electroplating bath, the flow guide is shown as a column with a square cross-section, such as... Figure 2 As shown. However, other shapes of guides can be used, and more specifically, other shapes of columns can be used. This is due to Figure 16 This example illustrates another possible cross-section of the column 140. Surface 142 has a convex curvature and intersects with concave surface 144 at edge 146. The electrolyte flows through the gap between edges 146, as shown by dashed lines, and is forced to change direction in doing so due to the arrangement of the column 140.

[0138] For the electrochemical process described above, in the presence of polymers or surfactants in the liquid electrolyte, the flow rate that can induce elastic turbulence can be detected by monitoring the current while gradually increasing the flow rate. When elastic turbulence begins, the increase in current flow will be significant due to the improved mass transport to or from the electrode.

[0139] However, the appropriate flow rate through the guide or porous electrode can also be determined without operating the half-cell. This is achieved by... Figures 18 to 20 Example. like Figure 18 As shown, structure 150 has dimensions suitable for surrounding the proposed flow guide 76, as in a half-cell, but without separators or membranes. Instead, plate 152 is fitted abutting the top of the column of flow guide 56. Inlet 160 is connected to pump 156, which delivers liquid from tank 154 maintained at a constant temperature. This liquid should be the same as the liquid flowing through the half-cell in the flow battery pack. Outlet 162 is connected to graduated container 158 for measuring the volume of liquid that has been pumped through flow guide 56 within selected time intervals, and thus determining the flow rate.

[0140] Pressure sensors 164 and 166 are mounted upstream and downstream of the flow guide 56 to the inlet and outlet regions of structure 150. When liquid from tank 154 is pumped through flow guide 56, a pressure drop will exist between inlet pressure sensor 164 and outlet pressure sensor 166. At very low flow rates, the flow will be laminar, without any elastic turbulence. By gradually increasing the pump speed to increase the flow rate and plotting the flow rate against the pressure drop or pump speed (which is proportional to the pressure drop), the minimum flow rate that induces elastic turbulence in the half-cell can be found. This plot will show the change in slope as the flow rate reaches the point where elastic turbulence begins.

[0141] This is illustrated by the following description of experimental work using equipment similar to that shown. The experimental results are as follows: Figure 19 and Figure 20 As shown. Initial calibration establishes the relationship between pump speed and flow rate. Tank 154 is filled with water. The pump is used to push the water through the half-cell at a gradually increasing flow rate. The pump speed and flow rate measured downstream of the half-cell are recorded and shown. Figure 19 (Triangle point). Then repeat the calibration procedure in jar 154 with an aqueous solution containing 0.1 wt% Floxaam 3630 polyacrylamide. This also gives... Figure 19 The nonlinear curve (dots) shown in the figure.

[0142] Figure 20The measured flow rate is shown as a plot against the pump speed. For water, the graph is approximately linear (as expected, since water is a Newtonian fluid), but for the polyacrylamide solution, the slope of the graph changes very sharply at point E, indicating the minimum flow rate at that point required to induce elastic turbulence with the polyacrylamide solution and equipment.

[0143] This measurement allows for the estimation of the Reynolds number of the flow through guide 56. A formula can be used to determine the Reynolds number (Re) of the flow through a chamber containing an obstruction, thus forcing the streamlines to bend:

[0144]

[0145] Where ρ is the fluid density in kilograms per cubic meter.

[0146] U is the flow velocity measured in meters per second.

[0147] L is the width of the gap between obstacles in the chamber, and

[0148] η is the fluid viscosity in Pascals per second.

[0149] If the flow velocity is measured as volume per unit time, then the above formula becomes

[0150]

[0151] Where Q is the flow velocity in cubic meters per second, and A is the cross-sectional area through which the flow passes, transverse to the overall direction of the flow.

[0152] In such Figure 11 In the example of the flow guide shown, the flat surface of the column has a width "a" of 4 mm, and the height of the column is 7 mm. The spacing "b" between the surfaces of adjacent columns is 2 mm, and therefore the gap between adjacent edges is √8 = 2.83 mm. A row of columns transverse to the overall flow direction contains 12 columns, with 11 gaps between edges 44, and therefore the cross-section available for flow is...

[0153] 11×7×2.83mm 2 =11 × 7.10 -3 ×2.83.10 -3 m 2 .

[0154] The flow rate was measured at 75 ml / s. -1 =7.5×10 -5 m 3 s -1 The density of the fluid is 1000 kg / m³. 3 The viscosity is 0.008 Pa·s. Substitute these figures into the above formula.

[0155]

[0156] Its Re = 12.17.

[0157] In embodiments of this disclosure using a flow guide, the flow velocity through the flow guide can result in a Reynolds number of at least 1 or 2 but not greater than 250. These are Reynolds numbers at which a Newtonian fluid, without additives to achieve elastic turbulence, would be in a laminar flow state.

[0158] Various embodiments of this disclosure have been described above. These embodiments are intended to aid in understanding this disclosure but do not limit it in any way. It should be understood that any feature or possibility described in any combination may be used individually where practically feasible. Furthermore, any feature or possibility mentioned in the following claims or described in any embodiment may be used in any other embodiment, provided that it is feasible to do so, and specifically, where two or more of the following claims are dependent on the same preceding claim, the reader should understand that this disclosure includes any two or more or all of those dependent claims in combination with each other and with any possible combination of the preceding claims.

[0159] Specifically, any rechargeable battery pack may use any polymer or any viscoelastic surfactant to achieve elastic turbulence in one or more of its half-cells, and may use flow guides with arrays of barriers or porous materials, or both, to induce a change in flow direction and thereby induce elastic turbulence. The rechargeable battery pack may use any electrochemistry mentioned herein for a half-cell in which solid deposits are present, and may use any structure and electrochemistry mentioned herein for another half-cell, with or without elastic turbulence.

Claims

1. A system comprising An electrochemical half-cell, the electrochemical half-cell comprising: Electrodes, and A liquid containing dissolved reactive substances, said dissolved reactive substances being capable of undergoing an electrochemical reaction at the electrode, wherein said reaction converts said reactive substances into a solid deposited at the electrode. A structure defining a liquid flow path, the structure carrying the liquid flow to contact the electrode, and At least one pump, the at least one pump being configured to propel the liquid along the flow path. in: The liquid contains a solute that enables it to exhibit elastic turbulence, and The flow path to or at the electrode is configured to force a change in the direction of liquid flow to induce elastic turbulence within the flow of the liquid in contact with the electrode.

2. The system of claim 1, wherein the solute that enables the liquid to exhibit elastic turbulence has a content of at least 10 6 Linear polymers with Dalton molecular weight.

3. The system of claim 1, wherein the solute that enables the liquid to exhibit elastic turbulence is a viscoelastic surfactant that forms worm-like micelles in the liquid.

4. The system according to claim 1, claim 2 or claim 3, wherein the liquid flow path includes a guide located near the electrode and includes a spaced array of barriers positioned to force the flow along the flow path to change direction.

5. The system according to any of the preceding claims, wherein the dissolved reactive substance comprises a compound of a metal from the group consisting of zinc, iron, nickel, lead, copper and tin, and wherein the deposit at the electrode is a solid metal.

6. The system according to any of the preceding claims, wherein the dissolved reactive substance comprises a metal compound, and the deposit at the electrode is a solid metal oxide or a metal hydroxide.

7. The system according to any of the preceding claims, wherein the half-cell is a half-cell of a rechargeable battery pack, and the system includes a storage container for the liquid connected to the at least one pump.

8. A rechargeable battery pack system, comprising The first electrochemical half-cell comprises: First electrode, and A liquid containing dissolved reactive substances capable of undergoing an electrochemical reaction at the first electrode, wherein the reaction converts the reactive substances into a solid deposited at the first electrode. A structure that defines a liquid flow path, the structure carrying the liquid flow to contact the first electrode. Storage container for the liquid, and At least one pump, configured to propel the liquid from the storage container along the flow path to contact the first electrode. The liquid contains a solute that enables the liquid to exhibit elastic turbulence, and the flow path to or at the first electrode is configured to force a change in the direction of liquid flow to induce elastic turbulence within the flow of the liquid in contact with the first electrode. and The second electrochemical half-cell includes: The second electrode, and A liquid containing a second dissolved reactive substance, which is capable of undergoing an electrochemical reaction at the second electrode. A structure defining a liquid flow path, the structure carrying the liquid flow to contact the second electrode. The storage container for the liquid used in the second half-cell, and At least one pump, the at least one pump being configured to propel the liquid from the storage container along the flow path to contact the second electrode.

9. The battery pack system according to claim 8, wherein: The liquid in the second half-cell further comprises a solute that enables the liquid to exhibit elastic turbulence, and The flow path to or at the second electrode is configured to force a change in the direction of liquid flow to induce elastic turbulence within the flow of the liquid in contact with the second electrode.

10. The battery pack system of claim 9, wherein the second dissolved reactive material is capable of undergoing an electrochemical reaction at the second electrode, the electrochemical reaction converting the second dissolved reactive material into a solid deposited at the second electrode.

11. The battery pack system of claim 10, wherein the first dissolved reactive substance comprises a metal compound, and the reaction at the first electrode converts the first reactive substance into a solid metal, the solid metal being deposited at the first electrode, and wherein the second dissolved reactive substance is a metal compound, and the reaction at the second electrode converts the second dissolved reactive substance into a solid, the solid being deposited on the second electrode as a metal oxide or a metal hydroxide.

12. A metal-air rechargeable battery pack system comprising a first electrochemical half-cell and a second electrochemical half-cell, with a separator membrane between the first half-cell and the second half-cell, wherein the first half-cell comprises: First electrode, A first liquid contains a dissolved reactive substance, which is a compound of a metal capable of undergoing an electrochemical reaction at the electrode, wherein the reaction converts the dissolved reactive substance into a solid metal deposited at the electrode. A structure defining a liquid flow path, the structure carrying the flow of the liquid to contact the first electrode, and at least one pump configured to propel the liquid along the flow path to contact the first electrode, wherein: The liquid contains a solute that enables the liquid to exhibit elastic turbulence, and the flow path to or at the electrode is configured to force a change in the direction of liquid flow to induce elastic turbulence within the flow of the liquid in contact with the electrode. And the second half-cell includes A second liquid, which is capable of undergoing an electrochemical reaction at one or more porous bodies within the second half-cell to form oxygen, wherein the one or more porous bodies in the second half-cell include a catalyst for the evolution of oxygen from water. A structure defining a liquid flow path, the structure carrying the flow of the second liquid to contact the one or more porous bodies, and At least one pump, said at least one pump being used to propel the second liquid along said flow path, in: The second liquid contains a solute that enables it to exhibit elastic turbulence, and The flow path is configured to force a change in the direction of liquid flow to induce elastic turbulence within the flow of the second liquid in contact with the one or more porous bodies that form oxygen.

13. The metal-air rechargeable battery pack system of claim 12, wherein the one or more porous bodies in the second half-cell further comprise a catalyst for reducing oxygen to water.

14. The metal-air rechargeable battery pack system of claim 12, further comprising a third half-cell and a separator membrane between the first half-cell and the third half-cell, wherein the third half-cell comprises one or more porous bodies containing a catalyst for reducing oxygen to water.

15. A method for operating a flow electrochemical half-cell, the flow electrochemical half-cell having an electrode in contact with a flow path of a liquid, the liquid containing a dissolved reactive substance capable of undergoing an electrochemical reaction at the electrode to convert the dissolved reactive substance into a solid deposited at the electrode, wherein: The liquid contains a solute that enables it to exhibit elastic turbulence. The flow path in contact with the electrode forces a change in the direction of liquid flow, and The method includes pumping the liquid along the flow path, wherein the liquid is in an elastic turbulent state when in contact with the electrode.

16. The method of claim 15, wherein the solute that enables the liquid to exhibit elastic turbulence has a content of at least 10 6 Linear polymers with Dalton molecular weight.

17. The method of claim 15, wherein the solute that enables the liquid to exhibit elastic turbulence is a viscoelastic surfactant that forms worm-like micelles in the liquid.

18. The method according to claim 15, claim 16 or claim 17, wherein the dissolved reactive substance comprises a compound of a metal from the group consisting of zinc, iron, nickel, lead, copper and tin, and the solid deposited at the electrode is the metal.

19. The method of claim 15, claim 16 or claim 17, wherein the dissolved reactive substance comprises a metal compound and the deposit on the electrode is a metal oxide or a metal hydroxide.

20. The method of any one of claims 15 to 19, wherein the half-cell is a half-cell of a rechargeable battery pack system including a storage container for the liquid, and the method further includes pumping the liquid from the storage container to the half-cell.

Images