Electrochemical cell with multi-planar electrolyte injection and active mass transport enhancement

Abstract

An electrochemical cell for a redox flow battery includes a multi-planar architecture with isolated inlet and outlet manifolds situated in separate, substantially parallel planes. A plurality of electrolyte injectors extend from the inlet plane, intersect the outlet plane, and provide point-wise delivery of electrolyte directly to a fluid-permeable electrode. This configuration structurally decouples electrolyte injection and extraction, mitigating channeling and pressure drops. The injectors may comprise conductive materials to function as current collectors. In further embodiments, the current collection system may be electrically coupled to a high-frequency (HF) excitation source. Regulated by a controller, this active excitation can be utilized to induce acoustic streaming at the electrode surface, thereby mitigating concentration polarization and reducing mass transport resistance during operation.

Description

[0001] Title of the Invention

[0002] Electrochemical Cell with Multi-Planar Electrolyte Injection and Active Mass Transport Enhancement.

[0003] Field of the Invention

[0004] The present disclosure relates generally to electrochemical energy storage systems. More particularly, it relates to flow field architectures and mass transport mechanisms for redox flow batteries.

[0005] Background and Problem Statement

[0006] Conventional electrochemical cells (Figure 1a, 1c) in redox flow batteries (RFBs) comprise an anodic and a cathodic half-cell. Each half-cell contains a fluid-permeable electrode (102) and a current collector (100). These current collectors are constructed from conductive materials and typically feature a carbon coating to withstand highly acidic or basic electrolyte environments. A separating membrane (103) is disposed between the respective electrodes to isolate the half-cells and prevent electrolyte cross-contamination. Uniformly distributing the electrolyte across the electrode, and subsequently the separating membrane, becomes increasingly complex as cell size increases. "Flow-through" architectures, where electrolyte is introduced to the electrode from a single point, quickly become inefficient at larger scales. Consequently, "flow-by" architectures utilize "flow frames" — manifolds or baffles containing surface grooves or channels (Figure 1b, 101) — to direct electrolyte flow and improve performance.

[0007] Flow frames typically comprise dual-purpose bipolar plates that feature structured channels on their electrode-interfacing surfaces. Conventional flow frames typically utilize grooves a few millimeters wide and deep to connect the inlet to the outlet. Common groove profiles include serpentine, parallel, and interdigitated designs (Figure 1d and 1e).

[0008] While parallel and serpentine configurations provide a direct fluid path, and interdigitated configurations force electrolyte through the electrode, these conventional flow fields fundamentally rely on a two-dimensional, co-planar arrangement. In these designs, the electrolyte enters and exits the cell from the same physical plane, providing essentially a co-planar electrolyte delivery system.

[0009] These co-planar configurations inherently tie the fluidic pressure gradient to the geometric plane of the electrode. As the active area scales, fluid inevitably follows the path of least resistance, bypassing denser regions of the fluid-permeable matrix and causing localized reactant starvation, a phenomenon known as channeling. Consequently, traditional designs suffer from three primary drawbacks: (1) high parasitic pumping losses due to excessive pressure drops across these tortuous paths; (2) non-uniform reactantdistribution leading to localized depletion and "dead zones"; and (3) limited mass transport at high current densities due to the formation of stagnant Nernstian boundary layers at the solid-liquid interface.

[0010] Attempting to resolve these issues by simply increasing the bulk pumping pressure exponentially raises parasitic energy consumption without guaranteeing uniform distribution. Furthermore, increased macroscopic flow velocity does not effectively disrupt the stagnant boundary layers at the micro-scale. Therefore, a structural and operational redesign is required to physically decouple the fluid injection plane from the extraction plane, while simultaneously providing a mechanism to actively mitigate concentration polarization at the electrode surface.

[0011] Brief Description of the Drawings

[0012] Figure 1a Is a schematic cross-section of a conventional flow-through electrochemical cell comprising an electrode and a current collector.

[0013] Figure 1 b Illustrates a conventional "flow-by" architecture utilizing flow frames to direct electrolyte flow. Figure 1c Depicts an exploded view of a standard conventional electrochemical cell stack assembly. Figure 1d Illustrates conventional flow frame groove profiles, including serpentine, parallel, and interdigitated designs (Reference: Performance Studies of Proton Exchange Membrane Fuel Cells with Different Flow Field Designs - Review || D0l:10.1002 / tcr.202000138 || License: CC BY 4.0). Figure 1e illustrates three-dimensional fluid flow simulations of the serpentine, parallel, and interdigitated designs groove profiles depicted in Figure 1d.

[0014] Figure 2a Shows a single half-cell multi-planar arrangement featuring an isolated inlet / outlet manifold, an active reaction zone, and conic shape extrusions functioning as direct electrolyte injectors.

[0015] Figure 2b Depicts the Split-Plane (SP) double half-cell architecture featuring a central, shared inlet manifold, separate outlet manifolds, and conic shape extrusions functioning as direct electrolyte injectors.

[0016] Figures 3a through 3d illustrate alternative geometric configurations for the electrolyte injectors: a staggered honeycomb array (Figure 3a), an aligned parallel grid (Figure 3b), arbitrary complex geometric cross-sections (Figure 3c), and elongated linear channels (Figure 3d)

[0017] Figure 4a is a schematic perspective view of a redox flow battery stack coupled to a high-frequency excitation control system.Figure 4b is an electrical schematic diagram illustrating a first power distribution configuration employing a series bias tee decoupling network for bidirectional isolation.

[0018] Figure 4c is an electrical schematic diagram illustrating a second power distribution configuration employing a parallel capacitive injection network.

[0019] Summary of the Invention

[0020] The present disclosure provides a "Split-Plane" (SP) electrochemical cell design that overcomes limitations of conventional designs by splitting inlet and outlet electrolyte flows into two different planes. The electrolyte enters the cell in an isolated inlet manifold within the cell body and reaches the active reaction zone through a plurality of dedicated extrusions. These extrusions act as electrolyte injectors, providing point-wise delivery of the electrolyte to the electrochemical cell’s electrode and the separating membrane of the positive and negative half-cells.

[0021] The location, shape and overall geometry of these extrusions may vary to optimize for specific fluid dynamic profiles and may include cylindrical, rectangular, tapered, or other arbitrary shapes (Fig. 3a-3d).

[0022] The outlet electrolyte is collected in a separate isolated manifold within the cell body, situated in a different plane than the inlet manifold. The inlet and outlet manifolds are fluidically coupled through the electrode, which is disposed in direct contact with, or in close proximity to, the respective manifolds. In a preferred embodiment, said electrode is a porous electrode; however, it may alternatively be a wire mesh, a 3D-printed lattice, a micro-grooved solid plate, or any other fluid-permeable medium.

[0023] This multi-planar arrangement enables the targeted delivery of electrolyte directly to the reaction sites while avoiding the pressure build-up typical of inlet-outlet interactions in co-planar designs.

[0024] Furthermore, the injecting extrusions can be constructed from conductive materials to serve as dualpurpose current collectors. In a preferred embodiment, these current collectors are coupled to an external excitation source capable of delivering high-frequency (HF) signals to the cell’s electrodes to improve mass transport through acoustic streaming and boundary layer disruption at the electrode’s interface.

[0025] Detailed Description of the Preferred Embodiments

[0026] Referring to Figure 2a, the present disclosure details a Split-Plane (SP) electrochemical half-cell comprising a body having an active reaction area, housing a separating membrane (206) bounding said active reaction area, at least one electrode (204) positioned adjacent to said separating membrane, with said electrode providing the medium where the active reaction area forms, and an electrolyte distribution system (207).The electrolyte distribution system (207), comprising an inlet manifold (202) and an outlet manifold (205), is positioned adjacent to the electrode (204). The inlet and outlet manifolds are disposed in at least two separate and substantially parallel planes within the body and are fluid ically coupled through the electrode (204), wherein an electrolyte is configured to flow through the said electrode. Furthermore, the electrolyte distribution system comprises a plurality of extrusions (203). These extrusions function as direct electrolyte injectors, extending from the inlet plane defined by the inlet manifold (202), intersecting the outlet plane defined by the outlet manifold (205), and delivering electrolyte point-wise directly to the electrode (204). This multi-planar architecture structurally decouples the electrolyte injection and extraction planes, mitigating channeling and minimizing bulk pressure drops. Furthermore, when constructed from conductive materials, these extrusions can act simultaneously as current collectors.

[0027] Referring to Figure 2b, to facilitate more compact deployments, the half-cell body may be configured with a central, shared inlet manifold (202) disposed between two separate outlet manifolds (205). In this stacked multi-planar arrangement, electrolyte fluid enters the shared central inlet manifold and is simultaneously directed outward in opposite directions through dual sets of electrolyte injectors (203), efficiently servicing two adjacent half-cells within a reduced spatial footprint.

[0028] Half-cells, such as those illustrated in Figures 2a and 2b, are combined in pairs (Figure 2a) or in triads (Figure 2b) to form Split-Plane (SP) electrochemical cells, which in turn may be assembled in series or in parallel to form redox flow battery cell stacks.

[0029] Furthermore, the isolated inlet manifolds (202) may comprise internal flow-distributing structures (not shown), such as microfluidic channels, baffles, or static mixers. These internal structures are configured to equalize hydrostatic pressure across the plurality of electrolyte injectors, thereby further ensuring uniform volumetric flow rates throughout the redox flow battery cell stack.

[0030] It should be understood that the geometry, as well as the spatial arrangement and density of the electrolyte injectors are not limited to the upward conic configuration depicted in Figures 2a and 2b. Rather, these structural parameters may be adapted to achieve specific fluid dynamic profiles across the electrode. For example, referring to Figures 3a through 3d, the injectors may, by way of example, comprise cylindrical structures positioned in a staggered, honeycomb array (3a) or in an aligned, parallel grid (3b). Furthermore, the extrusions may be configured with arbitrary or complex geometric cross-sections (304), or formed as elongated, linear channels (305).

[0031] Similarly, referring to Figure 2a, the fluid-permeable electrodes (204) may take various structural forms. While a standard porous electrode is utilized in a preferred embodiment, the electrode may alternatively comprise a conductive wire mesh, a 3D-printed lattice structure, a micro-grooved solid plate, or any other functionally equivalent fluid-permeable medium.Current collection from such fluid-permeable electrodes (204) can be configured in distinct embodiments relative to the electrolyte injectors (203).

[0032] In a first configuration, the electrolyte injectors (203) are constructed from conductive materials, allowing them to act simultaneously as current collectors.

[0033] In a second configuration, the electrolyte injectors (203) are constructed from non-conductive materials to act as electrical isolators and current collection is performed through a distinct network of conductive material directly integrated with, or disposed upon, the electrode (not shown).

[0034] Regardless of the specific structural implementation, either the current collectors or the distinct network of conductive materials directly integrated with, or disposed upon the electrode, establishes a robust current collection interface at half-cell level directly reaching each individual electrode (204) and the active reaction area formed in its surrounding.

[0035] When combining current collection from half-cells, cells and cell stacks, this interface functions as a current collection system configured to facilitate electrical current conduction between all electrodes and an external circuit.

[0036] While not strictly required for standard passive cell operation, this current collection system provides a physical mechanism for active mass transport enhancement. Specifically, in certain embodiments, this current collection system allows for the direct electrical coupling of the electrochemical cell stack to an external, dynamic excitation source to actively alter fluid behavior at the solid-liquid (electrode-electrolyte) boundary.

[0037] Referring to Figure 4, one embodiment of the electrochemical cell stack (400) in accordance with the present disclosure is shown with two inlet and two outlet connections (410) for the electrolytes (anolyte and catholyte). The current collection system (401) is coupled with an external High-Frequency (HF) Excitation Source (403), via a set of cables (402), to improve the electrochemical cell stack performance by actively mitigating concentration polarization. While traditional architectures rely exclusively on bulk electrolyte pumping to deliver reactants to the electrode surface, the presently disclosed electrochemical cell stack may be further configured to utilize HF excitation for inducing micro-scale agitation within the Nernstian boundary layer directly at the electrode surface. Through the utilization of HF excitation, the now active electrochemical cell stack induces localized fluid dynamics that accelerate ion transport beyond the limits of passive diffusion. This active mitigation of concentration polarization directly translates to a measurable increase in the limiting current density and an improved overall state-of-charge efficiency during high-rate operations.The electrical integration is achieved through a specialized power distribution network, as illustrated in Figures 4b and 4c, positioned between a primary power source or power load (representing the utility side) and the electrochemical cell stack. This network is designed to decouple the HF excitation source introduced alternating current (AC) and the electrochemical cell stack’s own direct current (DC) paths, ensuring the HF signal does not interfere with the primary power conversion electronics on the utility side. In one configuration, referring to Figure 4b, the HF excitation source is coupled via a bias tee where the DC path includes a low-resistance inductor. To ensure absolute bidirectional isolation, inductors may be disposed symmetrically on both the supply and return lines. These inductors, which may comprise specific busbar geometries or the application of ferrite sleeves around the primary conductors, provide sufficient electrical impedance to block the HF signal without introducing significant (l2R) losses to the DC flow.

[0038] Alternatively, referring to Figure 4c, the HF excitation source is coupled via a parallel capacitive injection configuration, utilizing a high-voltage capacitor bank to superimpose the HF signal while maintaining a strictly uninterrupted, series DC path.

[0039] The physical mechanism driving the enhanced mass transport is primarily governed by the Lorentz force interaction. As the HF signal propagates through the current collection system (401), its oscillating current (I) interacts with the magnetic fields (B) generated by the high-density DC flow of the electrochemical cell stack (400). This interaction creates a periodic mechanical force (F = I x B) that induces physical micromovement and vibration within the electrode structure. In turn, these vibrations dissipate momentum into the electrolyte, generating localized micro-convection (acoustic streaming) that physically thins the stagnant boundary layer and decreases mass transport resistance (Rmt).

[0040] To govern this active mass transport enhancement, the HF excitation source may be further operatively coupled to a controller (404). This controller is configured to energize the HF excitation source (402) at a frequency sufficient to induce the aforementioned acoustic streaming at the electrode surface, thereby actively reducing mass transport resistance during operation. Said sufficient frequency is predetermined or dynamically calculated utilizing acoustic streaming equations, relying on variables including the kinematic viscosity of the electrolyte, the speed of sound within the fluid medium, and the characteristic thickness of the Nernstian boundary layer. Alternatively, the controller may determine the optimal frequency empirically via real-time electrochemical impedance spectroscopy feedback. Furthermore, the controller may be configured to execute a frequency sweep to identify the natural acoustic resonance frequency of the electrolyte within the cell cavity, the natural mechanical resonance frequency of the electrode structure, or a coupled vibro-acoustic resonance thereof. Tuning the HF excitation source to these specific resonant frequencies maximizes both structural displacement and micro-scale fluid agitation amplitude while minimizing electrical energy input.From an operational standpoint, the deployment of the HF excitation source is designed to be power net positive. Because mass transport resistance dominates energy losses at high operating current densities, the active reduction in concentration overpotential yields a functional power gain that exceeds the electrical overhead of the HF excitation source. This provides a measurable increase in the overall round-trip efficiency of the electrochemical cell stack. Additionally, grid-scale, industrial, and residential applications, are characterized by a diurnal generation-demand mismatch. During charging opportunity times, power is available in oversupply (e.g. noon peak delivery of solar cells, or wind burst delivery of wind turbines), exceeding available consumption and storage potential. In such conditions, the energy utilized by the HF generator is drawn from power that would otherwise face curtailment, i.e. incurring no actual operational power penalty, rendering the proactive optimization of the electrochemical cell stack’s internal kinetics completely opportunity-cost neutral.

Claims

Claims1. An electrochemical half-cell for a redox flow battery, comprising:a body having an active reaction area;a separating membrane bounding said active reaction area;at least one electrode positioned adjacent to said separating membrane, said electrode providing the medium where the active reaction area forms;an electrolyte distribution system positioned adjacent to the said electrode comprising an inlet manifold and an outlet manifold;characterized in that said inlet manifold and said outlet manifold are disposed in at least two separate and substantially parallel planes within the body, fluidically coupled through the electrode; further comprising a plurality of electrolyte injectors of arbitrary shapes extending from the inlet plane defined by the inlet manifold, intersecting the outlet plane defined by the outlet manifold, and delivering electrolyte point-wise directly to the electrode; anda current collector or a current collection interface.

2. An electrochemical half-cell according to claim 1 , wherein the electrode is a porous electrode, a conductive wire mesh, a 3D-printed lattice structure, a micro-grooved solid plate, or any other functionally equivalent fluid-permeable medium.

3. An electrochemical half-cell according to claim 1 , wherein the electrolyte injectors are constructed from conductive materials and act simultaneously as current collectors.

4. An electrochemical half-cell according to claim 1 , wherein the electrolyte injectors are constructed from non-conductive materials, and said current collection interface comprises a network of conductive material integrated with or disposed upon the electrode.

5. An electrochemical half-cell according to claim 1 , wherein the inlet manifold further comprises internal flow-distributing structures.

6. A redox flow battery system having enhanced mass transport capabilities, the system comprising:an electrochemical cell stack containing at least one electrochemical cell comprising an anodic halfcell and a cathodic half-cell, each half-cell containing an electrode and a current collector or current collection interface;an electrolyte configured to flow through the said electrode;a high-frequency (HF) excitation source electrically coupled to the cell stack’s current collection system; anda controller configured to energize the HF excitation source at a frequency sufficient to induce acoustic streaming within the electrolyte at the electrode surface, thereby reducing mass transport resistance during operation.

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