A flexible, low-cost, small-volume flow cell test system and methods of using

Abstract

A compact, modular flow cell Test System / apparatus is disclosed for high-throughput evaluation of liquid-phase electrochemical systems and components using small volumes. The Test System includes one or more independently addressable test devices, each comprising a flow cell stack, reservoirs, and a pump subsystem configured to circulate electrolyte through the flow cell stack at selectable flow rates. One or more test devices may be disposed within an enclosure providing a controlled atmosphere with optional monitoring of oxygen, humidity, and temperature, and a scalable gas manifold may supply inert gas to one or more enclosures. The Test System supports static and recirculating operation, parallelization across multiple devices, and cell stack configurations including compressed near-zero-gap designs.

Description

[0001] A FLEXIBLE, LOW-COST, SMALL-VOLUME FLOW CELL TEST SYSTEM AND METHODS OF USING

[0002] CROSS REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit under 35 U.S.C. Section 119(e) of U.S. Provisional Application No. 63 / 753,388, filed February 3, 2025, by Nathan Daniel Kirchhofer and Maarten Arnold Rutgers, entitled “Development and validation of a flexible, low -cost, small-volume flow cell platform for high throughput flow battery research, development, and deployment,” attorney docket 298.0003USP1, which application is incorporated by reference herein.

[0004] BACKGROUND OF THE INVENTION

[0005] 1. Field of the Invention.

[0006] The present disclosure relates to electrochemical and bio-electrochemical test systems, and more particularly to compact flow battery test platforms suitable for high-throughput screening of electrolyte formulations, membranes, electrodes, other components, and operating conditions such as varying temperature or atmospheric composition.

[0007] 2. Description of the related art

[0008] Flow batteries are promising for grid-scale energy storage due to decoupled power and energy capacity, long cycle life, long discharge / charge cycles, inherent safety, domestic supply chains and manufacturing, and potential for low-cost active materials. However, conventional laboratory flow battery test hardware typically requires relatively large electrolyte volumes, bulky pumping and tubing infrastructure, and significant setup and assembly time. These constraints can impede rapid iteration on electrolyte formulations and component screening, particularly when the active materials, membranes, or additives are scarce or expensive.The idea of a flow batery Test System is not new. Related topic patents that show some schematic figures are often very similar for any component in the field (example can be seen in [1], Typically a flow batery test system is built from various off-the-shelf parts such as pumps, tubing, tubing fitings, botles, pump controller, and frame(s) to hold it all together. This hardware combination supports the heart of the Test System: a cell stack comprised of electrodes, flow fields, and ion permeable membrane(s) that enables the flow / control of electrical current and measurement / application of voltages. A Test System is typically cobbled together by researchers, and often no two designs, let alone individual devices, are alike. Certain cell stack designs can be purchased from a few vendors and are usually a somewhat complicated sandwich of metal, graphite, and plastic plates and many rubber gaskets between them all, typically clamped together with a constellation of bolts and nuts, all of which have to be tightened carefully. Such Systems typically take up a full lab bench, and often need to be housed in inert gas glove boxes which are the size of a lab bench. The costs are significant: $5k for the cell stack, $3k for the pump, $lk for the tubing and fitings, $20k for a very basic inert gas

[0009] glovebox. Systems typically require 1-10+ grams of proprietary / rare / expensive reagents, 50-100+ cmA2 of membrane materials, and 10-100+ mb of final electrolyte formulation per device. Ideally multiple experiments can be executed in parallel, and in commercial setings it is not unusual to desire 50 to 100 parallel Test Systems. The costs and lab space requirements quickly balloon. For instance, one current commercially available state of the art is shown in [2] . This system [2] sells for several $10k, takes up a full lab bench and the beter part of a basic glovebox system, requires -1000 mb of electrolyte, and has many bolts and fitings to tighten and service. A single person could not reasonably be asked to set up one per day.

[0010] An effort to miniaturize flow cell Test Systems, notably this

[0011] reference htps: / / iopscience.iop.org / article / 10.1149 / 1945-7111 / ad9bef, reported a reduced-size flow cell that used smaller screws, fitings, etc., but does not appear to achieve a very significant improvement because the overall idea recapitulates thesame tried design: many parts and gaskets clamped together with many

[0012] screws. Derivative approaches such as this will never reach the >10-fold improvements on so many fronts.

[0013] There have been other efforts to miniaturize flow cell Test Systems [3] which reported a reduced-size flow cell that used smaller screws, fittings, etc., but does not appear to achieve a very significant improvement because the overall idea recapitulates the same tried design: many parts and gaskets clamped together with many screws. Derivative approaches such as this will never reach the >10-fold improvements on so many fronts.

[0014] While small-volume test hardware can reduce material consumption and increase experimental throughput, but miniaturization can introduce challenges including increased sensitivity to dead volume, leaks, evaporation, oxygen ingress, variability in environmental conditions, variability in electrical contacts and interrogation of the system and components, and variability in user behavior.

[0015] Accordingly, there remains a need for integrated, low-volume flow electrochemical test systems that enable reliable, repeatable, replicable, reproduceable cycling and diagnostic measurements while remaining flexible across chemistries and operating modes. The present disclosure satisfies this need.

[0016] SUMMARY OF THE INVENTION

[0017] The present disclosure provides systems, devices, and methods for a modular flow electrochemical test system (the "Test System" 100) that enables high-throughput research, development, and validation of flow-based chemistries and componentry, in particular but not limited to Flow Batteries. The Test System 100 may be configured as one or more independently addressable test devices (e.g., device 400) that are electrically interrogated by an external data acquisition computer / controller 110 (for example, a potentiostat / galvanostat or other measurement controller).In various embodiments, each Device 400 includes: (i) a flow cell stack assembly 500; (ii) one or more reservoirs 430 for electrolyte; (iii) a pump assembly 420 configured to deliver electrolyte through the flow cell stack 500 at selectable flow rates; and (iv) fluidic interconnects 440 configured to minimize dead volume and enable rapid setup (Fig. 3, Fig. 6).

[0018] In some embodiments, one or more Devices 400 are placed in an inert gas box 200 that provides a controlled inert atmosphere for improved reproducibility and reduced oxygen exposure. The inert gas box 200 may include or support sensors 240 (for example, oxygen 242, temperature 244, and humidity 246 sensors) that may be passive (local display) or electrically addressed for readout by the external controller 110 or other circuitry (Fig. 1, Fig. 2).

[0019] In some embodiments, a gas manifold assembly 300 distributes inert gas to one or more inert gas boxes 200. The manifold 300 may include a pressure gauge 312 and per-branch flow control valves 330 to tune purge rates to individual enclosures (Fig. 4, Fig. 5).

[0020] In some embodiments, small electrolyte volumes (including sub-milliliter per side volumes), selectable flow rates (including sub-milliliter per minute), small active areas (including < 30 mmA2), and scalable parallelization (including 2-8+ devices addressed simultaneously) are implemented. The disclosed embodiments are compatible with a broad range of electrolyte formulations and may be used with organic or inorganic redox-active materials, including metal-based systems such as vanadium, as well as organic or inorganic solvents or liquids.

[0021] BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.Referring now to the drawings in which like reference numbers represent corresponding parts throughout:

[0023] Fig. 1: is a system block diagram of a Test System 100 showing independent electrical addressing / interrogation of each Device 400 by an external DAQ / controller 110 and computer 112, and showing electrolyte and inert gas subsystems.

[0024] Fig. 2A: is an overall Test System line drawing showing an Inert Gas Box 200 containing a Device 400 from a front perspective view and showing external gas connections and some subcomponents

[0025] Fig. 2B is an overall Test System line drawing showing an Inert Gas Box 200 containing a Device 400 from a rear perspective view showing external gas inlet and outlet connections and electrical power and signal feedthroughs

[0026] Fig. 2C is a line drawing of the Inert Gas Box Lid 212 with Gasket 214 and Clamp 216 used for affixing the Lid to the Inert Gas Box 200

[0027] Fig. 3: is a fluidic and gas handling schematic illustrating electrolyte routing between reservoirs 430, pump assembly 420, and flow cell stack 500, as well as inert gas routing from inert gas supply 202 to manifold 300 through flow control valves 330 to optional bubbler jars 352 to posolyte electrolyte reservoir 432 and negolyte reservoir 434.

[0028] Fig. 4: is a gas handling schematic illustrating inert gas distribution from an inert gas supply 202 to gas manifold assembly 300 to one or more inert gas boxes 200, optionally via a bubbler / humidifier jar assembly 350.

[0029] Fig. 5A: is a mechanical line drawing of a gas manifold assembly 300 from a front perspective view with an inlet 310, pressure gauge 312, and multiple outlet ports 320 with per-branch flow control valves 330 and per-branch on / off valves 332.

[0030] Fig. 5B: is a mechanical line drawing of a gas manifold assembly 300 from a rear perspective view with an inlet 310, pressure gauge 312, with per-branch on / off valves 332.Fig. 5C: is a mechanical line drawing of a gas manifold assembly 300 from a front perspective view gauge 312, and N outlet ports 320 with per-branch on / off valves 332.

[0031] Fig. 6A: is a line drawing of a device 400 from a front perspective view showing a pump assembly 420, reservoirs 430, electrolyte tubing 440, a device frame 410, oxygen sensor 242, and a flow cell stack assembly 500.

[0032] Fig. 6B: is a line drawing of a section view of the “fittingless” fitment of electrolyte tubing 440 (that has cladding 442) to a graphite block electrode 520 to create a cell stack inlet / outlet ports 590.

[0033] Fig. 6C: is a mechanical line drawing of a section view of the “fittingless” fitment of electrolyte tubing 440 (with cladding 442) into elastomer tubing 454 constricted by tubing constriction block 452 and affixed to a pump head with barb fitting 448.

[0034] Fig. 7A: is an exploded view of a flow cell stack assembly 500 showing electrodes 520, gasket(s) 540, membrane 530, current collectors 550, alignment features 560, a clamp block 570, electrolyte tubing 440, and representative fasteners.

[0035] Fig. 7B: is an assembled cross-sectional view of the flow cell stack assembly 500 showing compressed, near-zero-gap layering at the membrane 530 and representative flow ports 590 and internal flow regions 596.

[0036] Fig. 7C: is a mechanical line drawing of an assembled view of the flow cell stack assembly 500 showing an embedded reference electrode 559

[0037] Fig. 7D: is a mechanical line drawing of an exploded and assembled cross-sectional view of the cell stack assembly 500 showing graphite block electrodes 520, graphite felt electrodes 526, flow field 596, gaskets 540, membrane 530, current collectors 550, and reference electrode 559

[0038] Fig. 8: is a schematic illustration of a configuration with one Device 400 per inert gas box 200 and the ability to stack N Test Systems 100 for independentlycontrolled environmental conditions with independent electrical leads 140 for each device.

[0039] Fig. 9: is a schematic drawing of a repeatable unit-cell top-down layout of an inert gas box 200 showing scalable placement of N devices with independent electrical leads 140 for each device.

[0040] Fig. 10: is a flowchart describing a Method 600 of operating a mini flow cell test system illustrating assembly and operation steps for static mode 610 and recirculating mode 620 and cycling protocol 640 with stepped current 650 and output recording 660.

[0041] Fig. 11: shows representative charge / discharge cycling traces (with current setpoints indicated) for (A) 1.6 M vanadium electrolyte formulations under static mode 610 cycling conditions, (B) 0.6 M organic electrolyte formulations under static mode 610 cycling conditions, (C) 1.6 M vanadium electrolyte formulations under recirculating mode 620 cycling conditions, and (D) 0.127 M organic electrolyte formulations under recirculating mode 620 cycling conditions.

[0042] Fig. 12: shows representative coulombic efficiency (CE), voltaic efficiency (VE), and round-trip efficiency (RTE) outputs as a function of cycle number with stepped current density (increasing current density every 10 cycles) for (A) 1.6 M vanadium electrolyte formulations under static mode 610 cycling conditions, (B) 0.6 M organic electrolyte formulations under static mode 610 cycling conditions, (C) 1.6 M vanadium electrolyte formulations under recirculating mode 620 cycling conditions, and (D) 0.127 M organic electrolyte formulations under recirculating mode 620 cycling conditions.

[0043] Fig. 13: shows representative impedance spectroscopy data from the devices operated with the electrolyte formulations of Fig. 11 and Fig. 12, showing (A) 1.6 M vanadium electrolyte formulations under recirculating mode 620 cycling conditions in the charged (1.56 V) and discharged (1.10 V) state and (B) 0.127 M organic electrolyte formulations under recirculating mode 620 cycling conditions in the charged (0.85 V) and discharged (0.4 V) state.Figs. 14A-14C are schematics of a flow cell according to one or more embodiments, wherein Fig. 14A is a cross-sectional schematic showing the internal volume, Fig. 14B shows the tubing, and Fig. 14C shows the clamping fixture.

[0044] Figs. 15A-15B illustrate voltage response to current applied to the electrodes as measured using the system of Fig. 14A, wherein Fig. 15A shows repeated cycling for 8 cycles of charge and discharge shows repeatable behavior and the ability to address the electrolyte using the Redoxino™ flow cell testing platform, and Fig. 15B is a zoom in to smaller time scales on the same 8 cycles of data shows repeatable measures of open circuit voltage in the cell that corresponds to the final cell voltage at the end of each discharge and charge cycle.

[0045] Fig. 16 is a flowchart illustrating a method of making a flow cell according to one or more embodiments.

[0046] Fig. 17 is a flowchart illustrating a method of operating a system according to illustrative embodiments described herein.

[0047] DETAILED DESCRIPTION OF THE INVENTION

[0048] In the following description of the preferred embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration a specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention.

[0049] Technical Description

[0050] Definitions and Interpretation

[0051] The following definitions are provided to facilitate understanding of the disclosure. Unless otherwise indicated, the terms below are intended to be open-ended and to include their ordinary meaning in the art.• "Test System" 100 - the overall apparatus including one or more Devices 400, optionally one or more inert gas boxes 200, optionally a gas manifold assembly 300, and interfaces to an external controller 110 and power supply 120 (Fig.

[0052] 1, Fig. 2).

[0053] • "Device" 400 - a device module including at least a flow cell stack assembly 500, reservoirs 430, pump assembly 420, and electrolyte tubing 440 configured to circulate electrolyte through the flow cell stack (Fig. 3, Fig. 6).

[0054] • "Independently addressed / interrogated" - each Device 400 is individually connectable to an external controller 110 via its own independent electrical channel leads 140 such that electrochemical measurements and control may be performed for one device without requiring identical addressing of another device (Fig. 1).

[0055] • "Dead volume" V_dead - liquid volume that is not effectively exchanged through the active region during intended operation (e.g., trapped volumes in fittings, un-swept tubing sections, or comers).

[0056] • "Swept volume" V_swept - liquid volume that is actively exchanged through the device during pumping / circulation, for example within tubing, reservoirs, and the stack.

[0057] • "Internal volume" V intemal - the total liquid volume associated with a Device 400 including dead volume and swept volume; in some embodiments V_intemal = V_dead + V_swept.

[0058] • "Static mode" 610 - a mode in which electrolyte is not actively circulated during at least a portion of electrochemical measurement, or is circulated intermittently (Fig. 10).

[0059] • "Recirculating mode" 620 - a mode in which electrolyte is actively circulated through the flow cell stack 500 during at least a portion of electrochemical measurement (Fig. 10).• "Near-zero-gap" or "zero-gap" - a cell stack configuration in which electrode(s) 520 are arranged and compressed such that solution resistance between an electrode surface and the membrane / separator 530 is minimized (Fig. 7B).

[0060] Unless explicitly stated otherwise, numerical ranges are inclusive of endpoints, and values expressed as "about" or "approximately" include tolerances typical in the art for the given quantity and measurement method. The phrase "in some embodiments" indicates that the described feature may be included in at least one embodiment, and does not imply that all embodiments include the feature.

[0061] Example Embodiments

[0062] 1. System Overview

[0063] Referring to Fig. 1 and Fig. 2, a Test System 100 includes one or more Devices 400 configured for electrochemical testing of flow electrolytes using small liquid volumes. The Test System 100 is configured such that each Device 400 is independently addressed / interrogated by an external data acquisition computer / controller 110. In some embodiments, the external controller 110 includes one or more potentiostat channels configured to provide and measure current and voltage signals for each device 400. In other embodiments, the external controller 110 includes any measurement instrumentation capable of independently monitoring and controlling each device 400.

[0064] In one or more embodiments, the devices described herein are Redoxino™ devices [4],

[0065] In some embodiments, the Test System 100 is powered by a power supply 120 providing a DC voltage (for example, approximately 24 V) to power pump motors 426, motor drivers 428, and optional electronics. In some embodiments, the Test System 100 is designed to be compatible with off-the-shelf laboratory instrumentation and to be fabricated and assembled using a combination of machined parts, additive-manufactured parts (e.g., 3D-printed parts), and commercially available fluidic and electrical components.In some embodiments, the Test System 100 is configured as a portable benchtop system. In some embodiments, the system is configured as an open architecture that permits rapid swapping of membranes 530, electrodes 520, gaskets 540, tubing 440, reservoirs 430, and control electronics, thereby enabling high-throughput screening and iterative development.

[0066] 2. Operating Envelopes and Scalability

[0067] Electrolyte volume. In some embodiments, the Device 400 is configured to operate using a total electrolyte volume of no more than 1 mb. In some embodiments, each side of the device uses as low as 0.5 mb of electrolyte per side. In further embodiments, each side uses up to 2 mb or more per side. The selected volume may depend on reservoir selection, tubing length, and internal volume of the flow cell stack 500 and associated swept volume.

[0068] blow rates. In some embodiments, the pump assembly 420 is configured to circulate electrolyte at flow rates of no more than 1 mb / min. In some embodiments, the pump assembly 420 is configured to circulate electrolyte at flow rates between 1 and 10 mb / min. In further embodiments, the pump assembly 420 is configured to circulate electrolyte at flow rates greater than 10 mb / min. In some embodiments, flow rate is set by pump speed, tubing inner diameter, and tubing wall compliance.

[0069] Active cross-sectional area. In some embodiments, the active cross-sectional surface area inside the flow cell stack 500 is less than 30 mmA2. In a preferred embodiment, the active cross-sectional surface area is between 30 and 300 mmA2. In some embodiments, the active area is defined by a gasket cutout and / or by a flow field geometry.

[0070] Current magnitude and current density. In some embodiments, miniaturization enables high current densities at low absolute current magnitudes, enabling safe use of sensitive potentiostat ranges and high signal -to-noise measurements. In some embodiments, current density is selected based on active area and targetedkinetic / mass transport regimes, and may be stepped during a cycling protocol 650 (Fig. 12).

[0071] Parallelization and multiplexing. In some embodiments, the Test System 100 supports parallel / multiplexed operation by allowing two Devices 400 to be simultaneously electrically addressed / interrogated by the external controller 110. In some embodiments, three or four devices 400 are simultaneously addressed. In a further preferred embodiment, more than four devices 400 are simultaneously addressed. In all such embodiments, each device 400 remains independently addressed / interrogated through the external controller 110 (Fig. 1).

[0072] Footprint and stacking. In some embodiments, a single full Test System 100 has a bench footprint of approximately 28 cm by 33 cm. In other embodiments, two or more systems are stacked vertically (Fig. 8) to reduce footprint while maintaining independent addressing and, in some cases, independent environmental control.

[0073] Cost and manufacturability. In some embodiments, the system is designed to be fabricated using low-cost components and open fabrication methods. In some embodiments, a complete device has a bill of materials that is below approximately $500 perunit, depending on configuration and sensors.

[0074] 3 Electrolyte Formulations and Compatibility

[0075] The disclosed Test System 100 is configured to be formulation-agnostic. In some embodiments, an electrolyte includes an electrochemically active material dissolved in a solvent along with a supporting electrolyte material. The solvent may include water or another solvent (for example, one or more organic solvents or liquidphase materials). In some embodiments, the electrochemically active material is organic. In other embodiments, the electrochemically active material is inorganic, mixed organic-inorganic, or includes a metal such as vanadium. Supporting electrolytes may include salts, acids, bases, buffers, other ionic species, or materials that modulate conductivity.In some embodiments, the system is used to assess: (i) electrochemical reversibility and kinetics; (ii) crossover and self-discharge behavior; (iii) stability and degradation under cycling; (iv) membrane resistance and selectivity; (v) electrode polarization and wetting; and (vi) effects of flow rate and mixing. In some embodiments, the external controller 110 performs galvanostatic cycling, potentiostatic holds, polarization curves, cyclic voltammetry, and / or impedance spectroscopy (Fig. 11-13).

[0076] 4 Device or Apparatus or System 400

[0077] Referring to Fig. 6, the Device 400 includes a device frame 410 supporting a pump assembly 420, reservoirs 430, electrolyte tubing 440, and a flow cell stack assembly 500. In some embodiments, portions of the device frame 410 are formed as 3D-printed components and include bosses, slots, or features to mount the pump assembly 420, support reservoirs 430, route tubing 440, and provide strain relief for wires 132 and independent leads 140.

[0078] 4.1 Reservoir Subsystem 430

[0079] In some embodiments, reservoirs 430 include vials, bottles, or other smallvolume containers. Reservoirs may be selected to minimize headspace, reduce oxygen ingress, and provide repeatable filling. In some embodiments, each reservoir includes a cap assembly 436 with two ports: a pickup port 438 connected to tubing 440 for circulation, and a return port 439 connected to tubing 440 for return flow. In some embodiments, the cap assembly 436 includes grommets or compression fittings to seal around tubing.

[0080] In some embodiments, reservoirs 430 are held by vial holders 431 that are integrated into the device frame 410. In some embodiments, holders are interchangeable to accept different vial sizes. In some embodiments, reservoirs are removable for rapid swapping of electrolytes and cleaning.4.2 Pump Assembly 420

[0081] Referring to Fig. 3 and Fig. 6, the pump assembly 420 includes one or more peristaltic pumps configured to circulate electrolyte. In some embodiments, a dualchannel peristaltic pump is used, with a first channel assigned to a positive electrolyte loop and a second channel assigned to a negative electrolyte loop. In some embodiments, the pump includes a stepper motor 426, and pump speed is controlled by a motor driver 428.

[0082] Pump tubing 424 may be replaced or selected based on electrolyte compatibility. In some embodiments, pump tubing includes an elastomer selected for chemical resistance (e.g., Viton) and low permeability. In some embodiments, the pump assembly includes a housing 422 and a manual on / off interface 429 on the driver 428. In some embodiments, the on / off interface is actuated without opening an inert gas box 200, for example using a button presser 270 (an external actuator that mechanically actuates a switch inside the box).

[0083] Flow calibration. In some embodiments, a flow calibration procedure is performed by measuring flow rate using a flow meter 250 in a gas line (for purge) and / or by measuring electrolyte delivery over time from the pump. In some embodiments, pump speed setpoints are mapped to flow rates for a given tubing material and inner diameter. In some embodiments, flow restriction elements (e.g., needle valves or restrictors) are included to tune flow.

[0084] 4.3 Electrolyte Tubing and Fluidic Interconnects 440

[0085] Electrolyte tubing 440 fluidically couples reservoirs 430 to the pump assembly 420 and to the flow cell stack assembly 500 (Fig. 3, 6) via an electrolyte inlet tube 444 or electrolyte outlet tube 446. In some embodiments, the tubing includes inert polymer tubing in regions in contact with electrolyte, including fluoropolymers such as FEP or PTFE. In some embodiments, tubing includes cladding or sleeving 442 to provide kink resistance, improve handling, and prevent oxygen ingress into the electrolytes.In some embodiments, tubing fittings 448 include push-to-connect fittings, luer fittings, barbed fittings, or in a preferred embodiment, a pull-through “fittingless” compression fitment (Fig. 6) between the tubing 440 and the graphite electrode 520 (positive electrode 522 or negative electrode 524) to establish the half-cell inlet port 592 or half-cell outlet port 594 that access the flow regions 596 (Fig. 7).

[0086] In some embodiments, fittingless tubing connections result in a high chemically compatible, zero dead volume, low cost, and space saving solution for connecting compliant tubing to rigid objects (Fig. 6, Fig. 7). In a preferred embodiment (Figure 6B), electrolyte tubing 440, preferably FEP polymer tubing, can be fitted to solid objects like graphite electrode 520. A hole is drilled in the graphite in the range of 5 to 10% smaller than the outer diameter of the tubing. Before insertion the tubing is gripped, either with fingers or pliers or both, at a short section and stretched to multiple times its original length. The tubing is cut at the thin section and this thin section is fed through the undersized hole. Slowly the tubing is pulled through the hole until pulling resistance is encountered. Then the thinned section is pulled completely through and beyond the hole. The excess tubing is cut flush with the surface of the electrode, preferably with a number 10 scalpel blade. When done properly, the pull out force exceeds several pounds. The amount of liquid pressure in the system sufficient to dislodge the tubing exceeds the bursting pressure of FEP tubing. Hence the fittingless connection is stronger than any pressure the system might ever experience.

[0087] In some embodiments, the same technique is used to affix steel cladding (442) around the electrolyte tubing (440). Again, the tubing is stretched and cut to create a thin section that exceeds the length of the steel tubing. The electrolyte tubing is pulled through the steel tubing until the thinned section is completely pulled through. The steel tubing is then formed to the desired shape and one end is pulled through the graphite electrode 520 as described above. The other end is cut about 1 cm beyond the end of the steel tubing for further use.In some embodiments, another type of fittingless connection (Fig. 6C) is employed where the electrolyte tubing 440 connects with the elastomeric tubing 454. In the case of the preferred embodiment of the test system herein described it is where the electrolyte tubing connects to the pump. In Fig. 6C Constriction block 452 is designed to reduce the inner diameter of elastomer tubing 454 by a precise amount which results in a fitment between the elastomer tubing 454 and the electrolyte tubing 440 that is tight enough to provide sufficient sealing to prevent leaks during pump operation but not so tight to prevent smooth insertion and removal of the electrolyte tubing 440. The compression block also functions as a secondary containment reservoir in case a leak does occur between elastomer tubing 454 and electrolyte tubing 440. The volume of containment exceeds that of the total working volume of the flow battery system. The other end of the elastomer tubing 454 connects to a barbed fitting 448 which is part of the OEM pump head.

[0088] In some embodiments, fittings and tubing length are selected to minimize dead volume and to avoid trapping bubbles. In some embodiments, the system includes a priming procedure to remove bubbles from tubing and from flow regions.

[0089] 4.4 Electrical Subsystem and Wiring

[0090] In some embodiments, the Device 400 includes wiring 132 for power distribution to pump motor 426 and optional electronics, and includes separate electrical lead connections 140 to connect the flow cell stack assembly 500 to the external controller 110 (Fig. 1). In some embodiments, wiring includes a DC input connector 122 and internal distribution to pump drivers 428.

[0091] In some embodiments, each device includes two external electrical terminals 152 and 154 corresponding to positive and negative current collectors 552 and 554. In some embodiments, each device includes five or more electrical terminals 152, 154, 156, 158, 159 corresponding to positive and negative current collectors 552 and 554, positive and negative voltage sense leads 556 and 558, and one or more reference electrodes 559, as well as jumper wires 142, 144, 146, 148, and 149. Terminals maybe configured as binding posts, bullet connectors, banana jacks, or other connectors. In some embodiments, low-impedance connectors are preferred to reduce contact resistance and / or measurement error.

[0092] 4.5 Flow Cell Stack Assembly 500

[0093] Referring to Fig. 7A and Fig. 7B, in some embodiments the flow cell stack assembly 500 includes a layered / sandwich structure comprising current collectors 550, electrode blocks 520, one or more gaskets 540, and a membrane or separator 530. The stack 500 defines flow regions 596 that allow electrolyte to contact electrode surfaces while maintaining separation between positive and negative electrolytes via the membrane / separator 530.

[0094] Cell size. In some embodiments, the flow cell stack assembly 500 is configured with a nominal 30 mm form factor. In a preferred embodiment, the flow cell stack assembly 500 is configured with a nominal 40 mm form factor. In some embodiments, these dimensions correspond to the lateral dimensions of electrode blocks 520 and / or gasket cutouts defining the active region.

[0095] Electrode blocks. In some embodiments, electrode blocks 520 are resin-impregnated graphite. In a preferred embodiment, electrode blocks 520 are fuel-cell grade graphite and have a thickness of approximately 1 / 4 inch. In some embodiments, electrode blocks are machined to include flow ports 590 that align with gasket openings and tubing 440. In some embodiments, electrode blocks include flow channels, grooves, or manifolding features to distribute electrolyte across the active region. In some embodiments, electrode blocks include a groove or channel to house an embedded reference electrode to sense the potential of the electrode.

[0096] Membrane / separator. In some embodiments, the membrane / separator 530 includes an ion-exchange polymer membrane (for example, Nafion or equivalents) or other separators selected based on ionic conductivity, crossover, stability, and cost. In some embodiments, the membrane / separator is pre-soaked, rinsed, or conditioned prior to use.Gaskets and sealing. In some embodiments, one or more gaskets 540 provide sealing between electrode blocks 520 and the membrane / separator 530 and define flow boundaries. In some embodiments, gaskets include elastomers such as Viton or FFKM rubber. In some embodiments, multiple gaskets are stacked to tune internal volume, compression, and flow characteristics. In some embodiments, vacuum grease or other lubricants are used to improve sealing around an O-ring or gasket interface.

[0097] Compression, alignment, and clamp. In some embodiments, alignment features 560 include removable dowels or pins used during assembly to align layers and then are removed after assembly. In some embodiments, a clamp block 570 is modified to accept tubing and to provide uniform compression. In a preferred embodiment, a clamp / vise 580 may apply compressive force to maintain sealing. In some embodiments, the stack is assembled as a repeatable "cartridge" that can be swapped for cleaning or for rapid membrane / electrode changes.

[0098] Zero-gap / near-zero-gap configuration. In some embodiments, the stack 500 is configured as a zero-gap or near-zero-gap design such that active electrodes 520 minimize solution resistance between an electrode surface and the membrane 530. In some embodiments, such reduction is achieved by selecting gasket thickness and compression such that the electrolyte gap thickness between an electrode surface and membrane is minimized while maintaining flow and sealing functionality (Fig. 7B). In one or more embodiments, the zero gap or near zero gap provides a highly-conductive interface and can be measured with impedance spectroscopy as in Fig. 13 to confirm that the resistance (impedance) is in the single-ohm range or below.

[0099] Reference Electrode. In some embodiments, high-quality electrochemical measurements rely on a reference electrode 559 which measures the cell potential near the working electrode. Figures 7C and 7D show an embodiment where atypical reference electrode 559, in this case a 2mm diameter non-conductive tube tipped with an ionically-conductive frit and filled with a potassium chloride solution and silver wire with silver chloride coating, is centered in a cylindrical reference electrode port 557 drilled into the graphite electrode 520. The hole has a small step at the end whichprevents the electrode from protruding into the electrolyte flow path and graphite felt 526. The electrode is also held in place by an elastomeric O-ring 555 which is compressed by one of the clamping blocks 570. In some embodiments, compressing the entire cell stack also creates and simultaneous liquid tight seal around the reference electrode.

[0100] Interference Fit: An interference fit (also referred to as a friction fit or press fit) is a fastening method between tube and the hole in the electrode wherein the tube and the hole are held together through mechanical interference and frictional forces at the interface between contacting surfaces. The dimensions of the components are configured such that the tube (typically having an outer surface) has a dimension slightly larger (e.g., 5-10%) than the outer diameter of the hole. When dimensional interference exists, the interference creates mechanical compression and tension forces when the components are assembled, resulting in a secure connection that resists separation without requiring additional fasteners. The retention force is derived from the combination of the dimensional interference, the coefficient of friction between the contacting surfaces, the contact area, and the normal forces pressing the surfaces together and preventing any leakage of the electrolyte that would detrimentally impact performance of the electrochemical testing. In such embodiments, the interference-fit approach can reduce part count and simplify assembly by eliminating separate, discrete fluid fittings at device interfaces, which can be bulky, expensive, or both, and can introduce additional internal void volume and additional leak interfaces.

[0101] In small-scale liquid handling in general (lab fluidics, electrochemistry rigs, microfluidics-adjacent setups), there are a handful of families of such fittings / connections that are conventionally used, including barbed hose fittings, Luer slip or Luer-lock fittings, threaded fittings (e.g. tapered pipe thread fittings such as NPT / BSPT and associated adapters), compression fittings (e.g. ferrule-based fittings), face-seal or flat-bottom fittings (e.g. microfluidic or HPLC-style threaded port fittings that seal at a planar seat), and quick-disconnect couplers (e.g. valved and non-valvedcouplers). While such fittings may provide convenience or standardized interfacing, they may be disadvantageous in compact small-volume flow systems because they often increase system bulk and protrusion near the cell, dramatically increase bill-of-materials cost and procurement complexity, and introduce additional interfacial seals and crevice volumes. These added geometries can increase dead volume, create bubble -trapping features, increase flow resistance, and increase the number of potential leak paths or failure points. Additionally, some fitting types can require higher assembly torque or specialized tools, may be slower to assemble and disassemble during high-throughput experimentation, and may require additional adapters (for example, Luer-to-barb or thread-to-Luer adapters), further increasing size, part count, and internal void volume. Accordingly, in some embodiments, the use of interference-fit fluid connections at the flow cell interface provides a reduced-footprint, reduced-dead-volume, reduced-cost, and simplified-assembly alternative to conventional fitting-based approaches, particularly for small-volume electrolyte loops and parallelized test configurations.

[0102] Clamping Mechanisms. Example clamping mechanisms include, but are not limited to:

[0103] 1. Central screw clamp, where a bolt passes through aligned holes in the plate stack and tightens into a nut or threaded boss. Screw-based systems may include variations like wing nuts, knurled knobs, or captive screws to improve ergonomics and prevent parts from being misplaced.

[0104] 2. Another method is cam -based clamping, such as cam locks or eccentric levers. These mechanisms convert a small rotational input into a rapid, high-force clamping action. A cam lock at the center hole can quickly push down on a pressure plate to secure the entire stack without tools.

[0105] 3. Spring-based clamping mechanisms offer passive, self-adjusting force.

[0106] Compression springs, Belleville washers, or wave springs can bestacked under a nut or clamp block to maintain consistent preload even if plate thickness varies or thermal expansion occurs.

[0107] 4. External devices such as C-clamps, toggle clamps, or small vises can also be used to compress the stack at one central region. These are versatile and require no integrated hardware. Toggle clamps, for example, provide repeatable, quick-action locking with a preset force. Clamp blocks — machined or molded pads that distribute pressure evenly — are often used with these tools to avoid imprinting or bending the plates. Materials for clamp blocks may include aluminum (rigid and lightweight), steel (durable for high loads), or polymers like Delrin or nylon (to avoid marring surfaces)

[0108] 4.6 Inert Gas Box 200

[0109] Referring to Fig. 2, Fig. 4, Fig. 8, and Fig. 9, an inert gas box 200 provides a controlled environment for one or more Devices 400. The inert gas box 200 includes a container body 210 and lid 212 that together define an enclosed volume. A seal 214 (for example, a gasket or O-ring) may be disposed between the lid 212 and the body 210. Clamps or latches 216 may maintain closure and improve sealing.

[0110] Container construction. In one embodiment, the inert gas box 200 is built from a clear polycarbonate food container and a matching lid (for example, a Gastronorm-style container / lid). In a further embodiment, the inert gas box 200 is built from a clear polycarbonate food container and matching lid appropriately sized to match the number of devices simultaneously contained in the inert gas environment.

[0111] Gas ports. In some embodiments, the inert gas box 200 includes a gas inlet bulkhead 220 and a gas outlet bulkhead 222. In some embodiments, the outlet 222 is connected to an exhaust flow meter 250 and / or vent line 226. In some embodiments, silicone tubing or other adapters are used to couple fittings to a flow meter or to thicker tubing.Electrical feedthroughs. In some embodiments, electrical feedthroughs 230 are provided for connecting each Device 400 to the external controller 110 without opening the enclosure (Fig. 2). In one embodiment, a feedthrough includes a stainless steel or brass screw 232. In another preferred embodiment, a feedthrough includes a push connector 234. In a most preferred embodiment, a feedthrough includes a low-impedance 2 mm connector 236, such as a gold-plated bullet-style barrel connector.

[0112] Power entry and daisy chaining. In some embodiments, the inert gas box 200 includes a power entry connector (for example, a barrel jack) and internal wiring to deliver power from the power supply 120 to devices within the enclosure. In some embodiments, power is daisy chained to a neighboring enclosure via a jumper cable 238 (Fig. 8).

[0113] Sensors. In some embodiments, sensors 240 include an oxygen sensor 242, a temperature sensor 244, and / or a humidity sensor 246. In one embodiment, a sensor is passive and provides local display. In a preferred embodiment, one or more sensors are electrically addressed to provide readout to the external controller 110 or to onboard circuitry.

[0114] Multi -device embodiments. In one embodiment, one device 400 is enclosed in one inert gas box 200. In another embodiment, two or more devices 400 are enclosed in one box. In another embodiment, one, two, or more than two and preferably as many as eight or more devices 400 are enclosed in one inert gas box 200. In some embodiments, devices are enclosed separately to allow independent temperature, humidity, and oxygen control. In other embodiments, multiple devices share one box to ensure replicate conditions.

[0115] Onboard control electronics. In some embodiments, an inert gas box 200 includes onboard circuitry or a controller to separately control pump motors 426, read temperature sensors 244, control temperature read oxygen sensors 242, and read other sensor outputs for each device 400 separately, while maintaining independent electrochemical interrogation via the external controller 110 (Fig. 1).4.7 Gas Manifold Assembly 300

[0116] Referring to Fig. 4 and Fig. 5, a gas manifold assembly 300 distributes inert gas to one or more inert gas boxes 200. In some embodiments, inert gas is provided from a pressurized source and regulated to a suitable pressure. The manifold assembly 300 includes an inlet 310, optional pressure gauge 312, and multiple outlet ports 320. In some embodiments, each outlet includes a flow control valve 330 configured to independently adjust purge flow to a corresponding branch line 322.

[0117] In some embodiments, the manifold assembly 300 is modular, such that additional outlet ports 320 may be added by repeating a manifold unit. In some embodiments, outlet fittings include 1 / 4 NPT interfaces, push-to-connect fittings, and tubing sized for low-flow purge. In some embodiments, check valves or filters are included to prevent backflow or contamination.

[0118] In some embodiments, a bubbler / humidifier jar assembly 350 is included to humidify purge gas or to provide visual confirmation of flow by bubbling through a liquid 354 in a container 352 (Fig. 4).

[0119] 4.8 Repeatable Multi-Device Layout in a Shared Inert Environment Referring to Fig. 9, a shared inert environment may be configured to hold multiple devices 400 using a repeatable unit-cell layout 290. In some embodiments, each unit cell corresponds to a device footprint and includes routing for an independent device leads 140. The inert gas box 200 may be sized to include N unit cells, where N may be 1, 2, 3, 4, 8, or more, including preferred embodiments where four or more devices are contained in one enclosure.

[0120] In some embodiments, the shared box contains multiple identical Devices 400 to ensure replicate conditions. In other embodiments, the shared box contains devices with different membranes, electrodes, electrolytes, or other features to enable side-by-side comparisons and control experiments under identical environment. In all embodiments, each device remains independently addressed / interrogated through the external controller 110 and independent leads 140.4.9 Electrical Addressing. Leads, and Connectors

[0121] As shown in Fig. 1 and Fig. 2, each device 400 is independently addressed / interrogated by the external controller 110. In some embodiments, each device includes positive and negative current collectors 552 and 554 that are connected through feedthrough(s) 230 to the external controller 110. In some embodiments, the external controller includes separate potentiostat channels. In other embodiments, switching hardware is used to multiplex a smaller number of channels across devices while preserving independent interrogation.

[0122] In some embodiments, electrical connections are made using clip-based connectors (e.g., alligator clips) for flexibility. In other embodiments, connectors are standardized and keyed for repeatability, including bullet connectors. In some embodiments, wiring is routed to minimize noise and to reduce parasitic resistance and inductance, which may be particularly important for impedance measurements (Fig. 13).

[0123] 4.10 Methods of Assembly and Operation

[0124] Referring to Fig. 10, methods are disclosed for assembling and operating a Test System 100. In some embodiments, assembly includes: (i) assembling the flow cell stack assembly 500 (Fig. 7A, Fig. 7B); (ii) installing reservoirs 430; (iii) routing tubing 440 and connecting to pump assembly 420; (iv) performing leak checks; (v) optionally installing the device in an inert gas box 200; (vi) purging the box; and (vii) connecting each device to the external controller 110 for independent interrogation.

[0125] Priming and bubble management. In some embodiments, the method includes priming tubing and the flow regions 596 to remove trapped gas. In some embodiments, flow is started at a low rate and increased after confirmation of continuous flow. In some embodiments, reservoirs are gently agitated to release bubbles. In some embodiments, tubing routing is selected to reduce high points that trap bubbles.Operating modes. In some embodiments, tests include static mode 610 (for example, no circulation during charge / discharge steps) and recirculating mode 620 (for example, continuous circulation during cycling). In some embodiments, circulation is intermittent, such as only during rest steps or only during portions of a cycle, to probe mass transport effects.

[0126] Environmental control. In some embodiments, the inert gas box 200 is purged for a defined period or until an oxygen sensor indicates a target oxygen level. In some embodiments, humidity is controlled via a bubbler / humidifier jar assembly 350 or via desiccants. In some embodiments, temperature is monitored and controlled using heaters, thermoelectric modules, or environmental chambers.

[0127] Data acquisition. In some embodiments, the external controller 110 performs and records galvanostatic cycling (Fig. 11), computes efficiencies (Fig. 12), and performs impedance spectroscopy (Fig. 13). In some embodiments, current density is changed every 10 cycles, and efficiency metrics are tracked overtime.

[0128] 4.11 Additional Embodiments and Variants

[0129] Stack variants. In some embodiments, the stack 500 includes alternative membrane types, alternative electrode chemistries (including porous carbon felt layers), or alternative current collector geometries. In some embodiments, the active area is tuned by changing a gasket cutout. In some embodiments, the stack includes serpentine, interdigitated, or parallel flow fields.

[0130] Fluidic variants. In some embodiments, reservoirs are configured for degassing or for pressurization. In some embodiments, the device includes valves to isolate the stack or to allow swapping reservoirs without draining tubing. In some embodiments, the device includes a bypass line to circulate electrolyte without passing through the stack.

[0131] Electronics variants. In some embodiments, device-level electronics include microcontrollers, pump drivers, and sensor interfaces. In some embodiments, the inert gas box controller provides closed-loop control for pump speed and environmentalparameters. In some embodiments, a networked interface provides device identification and logging for high-throughput experimentation.

[0132] Materials. In some embodiments, wetted components are selected to be chemically inert to the electrolyte chemistry under test, including fluoropolymer tubing, chemically resistant fittings, graphite electrodes, and resistant gasket materials. In some embodiments, components are selected to reduce oxygen permeability and solvent loss, particularly for oxygen-sensitive organic electrolytes.

[0133] 5. Non-Limiting Examples and Representative Data

[0134] The following examples are provided to illustrate operability of the disclosed embodiments and are not intended to limit claim scope. Experimental details may be varied without departing from the spirit of the disclosure.

[0135] 5.1 Example: Aqueous-Soluble Organic Electrolyte Cycling (Representative) In a representative example, an aqueous-soluble organic electrolyte is formulated with an electrochemically active organic material dissolved water along with a supporting electrolyte. In some embodiments, two concentrations are evaluated, approximately 0.1 M and 0.6 M of the electrochemically active material (Fig 11, 12, 13). In preferred embodiments, the organic material formulation is at a concentration above 1.0 M. In some embodiments, the device 400 is operated in static mode 610 and in recirculating mode 620. Representative charge / discharge cycling traces for the organic electrolyte conditions are shown in Fig. 11, including examples multiple both concentrations and at both static and recirculating operation.

[0136] Representative coulombic efficiency (CE), voltaic efficiency (VE), and round-trip efficiency (RTE) plots versus cycle number are shown in Fig. 12. In some embodiments, current density is changed every 10 cycles to probe performance sensitivity to operating conditions (Fig. 12). Optional impedance spectroscopy data for selected states of charge and / or cycle numbers are shown in Fig. 13.52 Example: Vanadium Electrolyte Cycling (Representative)

[0137] In another representative example, an inorganic metal-based electrolyte is evaluated. In some embodiments, the electrochemically active material includes vanadium. In a representative embodiment, a vanadium electrolyte of approximately 1.6 M is evaluated in static mode 610 and recirculating mode 620. Representative cycling traces are shown in Fig. 11 (vanadium traces), representative efficiency plots are shown in Fig. 12, and optional impedance spectroscopy data are shown in Fig. 13.

[0138] 5.3 Example: Small-Volume Symmetric Cycling (Representative)

[0139] In some embodiments, the system is used to perform proof-of-principle cycling using small-volume symmetric formulations where the same formulation is provided on both sides of the cell. Such examples may be used to validate repeatability, open-circuit voltage behavior, material stability under intense cycling, and independent electrical addressing across devices.

[0140] 6. Industrial Applicability

[0141] The disclosed Test System 100 provides a compact, low-volume, scalable platform for electrochemical experimentation in which liquid-phase reagents are circulated through a flow cell stack 500 under controlled electrical interrogation by an external controller 110 (Fig. 1-3, Fig. 7). While certain embodiments are described in connection with redox flow battery research and development, the disclosed apparatus and methods are not limited to flow batteries and may be applied broadly to other research, development, screening, and validation workflows where small volumes, controlled flow, parallelization, and optional atmosphere control are beneficial.

[0142] In some embodiments, the Test System 100 is used as a small-volume flow electrochemistry platform for screening or development of electrochemical reactions in which one or more reagents are dissolved in a solvent with a supporting electrolyte and circulated through the flow cell stack 500 (Fig. 3, Fig. 6-7). Such applications may include, by way of non-limiting example, organic electrosynthesis and relatedelectrocatalytic reaction development where controlled current density, selectable flow rate, and small reagent volume enable rapid condition screening, including screening across multiple Devices 400 operated in parallel (Fig. 1, Fig. 9). In some embodiments, the system is used to screen redox mediators and soluble catalysts for oxidation / reduction processes, including evaluation of mediator stability, efficiency, and compatibility with membranes 530 and electrode materials 520 (Fig. 7, Fig. 11-13).

[0143] In some embodiments, the Test System 100 is used for electrochemical evaluation of electrolyte-dependent conversion processes in flowing electrolytes, including screening of electrocatalyst / electrolyte interactions, polarization behavior, stability under cycling, and transport-limited regimes as a function of flow rate and current density. Such applications may include, by way of non-limiting example, electrochemical conversion of dissolved species (including inorganic or organic reactants) in aqueous or non-aqueous supporting electrolytes and may be conducted in static mode 610 and / or recirculating mode 620 (Fig. 10), and optionally characterized using cycling, efficiency, and impedance measurements (Fig. 11-13).

[0144] In some embodiments, the Test System 100 is used as a platform for analytical electrochemistry and electrochemical sensing under controlled flow, including calibration and comparative testing of sensing electrodes and membranes / separators in a two-compartment format. Controlled flow and small volume may improve repeatability and reduce reagent consumption for sensing and analytical workflows, and parallelization may enable replicate measurements under matched conditions (Fig. 1, Fig. 9). In some embodiments, the Test System 100 is used to evaluate sensor behavior under controlled oxygen exposure using an inert gas box 200 and associated sensors 240 (Fig. 2, Fig. 4, Fig. 8-9).

[0145] In some embodiments, the Test System 100 is used for materials compatibility screening and related electrochemical materials evaluation, including corrosion testing, stability testing, and compatibility screening of current collectors 550, electrodes 520, membranes 530, and gasket materials 540 under controlled electrolyteexposure and cycling protocols (Fig. 7). In some embodiments, the system is used to evaluate changes in resistance, polarization, or leakage behavior over time as a function of electrolyte composition and operating conditions, including stepped current density protocols 650 (Fig. 12) and optional impedance spectroscopy (Fig. 13).

[0146] In some embodiments, the Test System 100 is used for membrane and separator research beyond flow batteries, including evaluation of ionic resistance, permeability / crossover behavior, solvent compatibility, and degradation under electrical bias in two-compartment liquid systems separated by a membrane / separator 530 (Fig. 7). In some embodiments, the system is used for screening and qualification of separators, ionomers, polymer membranes, and composite membranes, including comparisons performed in parallel across multiple devices (Fig. 1, Fig. 9) and / or under controlled atmosphere conditions in an inert gas box 200 (Fig. 2, Fig. 8-9).

[0147] In some embodiments, the Test System 100 is used for general electrolyte stability and impurity tolerance studies in electrochemical systems, including evaluation of the influence of oxygen exposure, water content, additives, contaminants, and supporting electrolyte composition on electrochemical reversibility, efficiency, and impedance behavior. Such characterization may be performed using representative cycling profiles (Fig. 11), efficiency tracking (Fig. 12), and optional impedance diagnostics (Fig. 13), and may benefit from controlled environmental conditions provided by an inert gas box 200 (Fig. 2, Fig. 4, Fig. 8-9).

[0148] In addition to the foregoing, the Test System 100 may be used in biological and bioelectrochemical research applications where small-volume, controlled-flow electrochemical environments are useful. In some embodiments, the Test System 100 is used for bioelectrochemistry and related in vitro screening of redox-active biochemical species, including non-limiting examples such as redox mediator screening, electrochemical evaluation of redox-active organic or biological molecules, and studies of oxygen-sensitive redox behavior conducted within a controlled atmosphere enclosure (Fig. 2, Fig. 4). In some embodiments, the Test System 100 isused for research involving microbial electrochemical systems, including comparative testing of electrochemical behavior under controlled flow and / or controlled atmosphere, and for parallelized replicate studies across multiple independently interrogated devices (Fig. 1, Fig. 9). In some embodiments, the Test System 100 is used for flow-based biochemical or environmental sensing studies, including nonlimiting examples in which electrochemical signals are measured under controlled flow to improve repeatability and enable rapid screening of conditions. In some embodiments, the Test System 100 is adapted for perfusion-style or exposure-style laboratory research workflows in which liquid media is circulated through a defined electrochemical or material interaction region for comparative studies, including replicate studies in shared or independent environmental enclosures (Fig. 8-9), while maintaining independent electrical interrogation (Fig. 1).

[0149] Accordingly, the disclosed Test System 100 and associated methods provide industrial applicability and utility across a wide range of electrochemical research and development fields, including but not limited to energy storage, electro-organic synthesis, electrocatalysis, analytical sensing, materials evaluation, membrane / separator development, electrolyte stability research, and bioelectrochemical and biological research workflows. The foregoing applications are provided as non-limiting examples, and other applications will be apparent to those skilled in the art.

[0150] Reference Numeral Scheme

[0151] This reference numeral scheme is designed to be consistent across all drawings, expandable for future variants, and easy to use when drafting the specification and claims. Numerals are grouped by subsystem using the hundreds series.100-series — Overall system and connection interfaces

[0152] Reference Description

[0153] numeral

[0154] 100 Test system (overall apparatus)

[0155] 110 External data acquisition / DAQ / controller (potentiostat) 112 External computer

[0156] 120 Power supply (e.g., 24 V supply)

[0157] 130 Electrical harness / wiring loom (general)

[0158] 132 Wiring for power distribution to pump motor

[0159] 140 Independent test channel leads (e.g. one device’s 5 electrical connections)

[0160] 142 Internal positive electrode current collector jumper wire

[0161] 144 Internal negative electrode current collector jumper wire

[0162] 146 Internal positive electrode voltage sense jumper wire 148 Internal negative electrode voltage sense jumper wire 149 Internal reference electrode jumper wire

[0163] 150 External electrical terminals / controller interface port(s) / connectors (general)

[0164] 152 External positive electrode current collector connection

[0165] 154 External negative electrode current collector connection

[0166] 156 External positive electrode voltage sense connection 158 External negative electrode voltage sense connection 159 External reference electrode connection200-series Inert gas box (environmental enclosure)

[0167] Reference Description

[0168] numeral

[0169] 200 Inert gas box (enclosure assembly)

[0170] 202 Inert Gas supply

[0171] 210 Container body (clear polycarbonate container)

[0172] 212 Lid

[0173] 214 Seal / gasket (perimeter seal; O-ring loop, etc.)

[0174] 216 Clamp(s) / latch(es)

[0175] 220 Gas inlet bulkhead / inlet fitting

[0176] 222 Gas outlet bulkhead / outlet fitting

[0177] 224 Internal gas distribution line (inside box, if shown)

[0178] 226 Exhaust / vent line to ambient (if shown)

[0179] 230 Electrical feedthrough (generic)

[0180] 232 Feedthrough fastener type (screw-style embodiment) 234 Feedthrough push connector (preferred embodiment) 236 Feedthrough low-impedance 2 mm connector (most preferred) 238 Power jumper cable

[0181] 240 Sensor module (generic)

[0182] 242 Oxygen sensor

[0183] 244 Temperature sensor

[0184] 246 Humidity sensor

[0185] 248 Pressure sensor (optional)

[0186] 250 Flow meter (box exhaust flow meter)

[0187] 260 Internal mounting bracket(s) (sensor / fixture mounts) 270 External Button presser / actuator

[0188] 280 Stacking feature (if depicted)

[0189] 290 Internal layout “unit cell bay” region (for scalable multi-device box layouts)300-series — Gas manifold and gas supply accessories

[0190] Reference Description

[0191] numeral

[0192] 300 Gas manifold assembly

[0193] 310 Manifold inlet

[0194] 312 Pressure gauge

[0195] 314 Regulator (if shown)

[0196] 316 Gas flow on / off valve (entire manifold)

[0197] 320 Manifold outlet port (generic)

[0198] 322 Branch line (to a box)

[0199] 330 Flow control valve (per-branch)

[0200] 332 Gas flow on / off valve (per-branch)

[0201] 340 Quick-connect / push-to-connect fitting (gas) 350 Bubbler / humidifier j ar assembly (general) 352 Bubbler container / jar

[0202] 354 Bubbler liquid (e.g., water)

[0203] 360 Tubing (gas) (general)

[0204] 370 Mount / frame / threaded rod structure (if depicted)

[0205] 400-series — Device (pumps, reservoirs, frame)

[0206] Reference Description

[0207] numeral

[0208] 400 Device module (overall)

[0209] 410 Device frame

[0210] 420 Pump assembly (overall)

[0211] 422 Pump housing

[0212] 424 Pump tubing segment

[0213] 426 Pump motor428 Pump motor driver / controller (e.g., stepper driver board)

[0214] 429 Pump controller on / off interface (switch / button) 430 Reservoir(s) (generic)

[0215] 431 Vial holder(s)

[0216] 432 Positive electrolyte reservoir

[0217] 434 Negative electrolyte reservoir

[0218] 436 Reservoir cap / septum (if shown)

[0219] 438 Electrolyte reservoir pickup port

[0220] 439 Electrolyte reservoir return port

[0221] 440 Electrolyte tubing (general)

[0222] 442 Tube cladding / sleeving

[0223] 444 Electrolyte inlet tube

[0224] 446 Electrolyte outlet tube

[0225] 448 Tube fitting (generic)

[0226] 450 Tubing guide / strain relief / clamp block (if shown) 452 Tubing constriction block for elastomer tubing 454 Elastomer tubing

[0227] 460 Device sensor mount (if sensors are mounted on device rather than box)

[0228] 500-series Flow cell stack and clamp (electrochemical cell) Reference Description

[0229] numeral

[0230] 500 Flow cell stack assembly

[0231] 520 Electrode block (graphite)

[0232] 522 Positive electrode

[0233] 524 Negative electrode

[0234] 526 Graphite felt electrode (conductive felt / fabric)530 Membrane / separator

[0235] 540 Gasket, elastomer (generic)

[0236] 542 First gasket

[0237] 544 Second gasket (stacked / doubled embodiment) 550 Current collector

[0238] 552 Positive current collector

[0239] 554 Negative current collector

[0240] 555 Reference Electrode O-ring

[0241] 556 Positive voltage sense connector

[0242] 557 Reference Electrode Port

[0243] 558 Negative voltage sense connector

[0244] 559 Reference electrode

[0245] 560 Alignment feature (dowel / pin / bore)

[0246] 570 Clamp block / compression plate (vise interface block) 580 Clamp / vise (if shown)

[0247] 590 Flow port (cell stack inlet / outlet ports at cell) 592 Internal half-cell inlet port

[0248] 594 Internal half-cell outlet port

[0249] 596 Flow channel / region (internal, schematic)

[0250] 600-series — Methods, modes, and measurement (optional labels) Reference Description

[0251] numeral

[0252] 600 Method of operating a mini flow cell test system 610 Static mode

[0253] 620 Recirculating mode

[0254] 630 Purge / inerting step (generic)

[0255] 632 Inert gas purge of electrolyte

[0256] 634 Inert gas purge of inert gas box640 Cycling protocol step

[0257] 650 Stepped current density schedule

[0258] 660 Measurement outputs (V, I, CE / VE / RTE, etc.)

[0259] Advantages and Improvements

[0260] The present disclosed / invented Test System improves many of the above mentioned metrics by 10-fold:

[0261] • The entire system can operate on 0.5 -2.0 mb of electrolyte per side, 10-200X less than state of the art systems requiring 10+ mb per side

[0262] • It requires ~2-5 cmA2 of membrane, lOx less than your typical small system requiring -30-50+ cmA2 membrane to assemble

[0263] • Including the inert gas box, the Test System occupies <1 cubic foot and <0.1 mA2 of footprint area, and can be stacked. A typical laboratory layout will therefore easily accommodate 4 parallel systems, even 8 when stacked, on a single benchtop, representing a >10X higher lab space utilization compared to a glovebox that requires >10 cubic feet and >1 mA2 of footprint are.

[0264] • A cell stack can be assembled, installed, and integrated into a Test System in under 2 minutes, fdled with electrolyte in 1 minute and set to run. This is easily >10X faster than the state of the art that can take 30+ minutes to assemble.

[0265] • The cell stack is sealed with only a single screw-based clamp vise, >10x less complex than the usual that typically requires 8 nuts and 8 bolts

[0266] • All tubing connections are of a novel “fitting-less” design achieved with compression fits between parts. This is important because miniaturization is often limited by the sheer size of fittings required to connect tubing to pumps and electrodes. In the present case the complete elimination of such fittings means smaller and less costly assembly (e.g. a good miniature fitting can cost $30, which is

[0267]

[0268] • Because of dramatic simplification and miniaturization, cost is also much lower. As described above, a typical commercial state of the art system costs ~$30k, of which the glovebox is easily ~$20k+. This fully sealed Test System can profitably sell for a $3k price, 1 / I Oth the cost. This does not even account for the significantly lower operator cost and floor space cost.

[0269] • The disclosed embodiments are compatible with electrolyte formulations including organic and inorganic redox-active materials and may be used for flow battery (FB) research (e.g,. as described in [5]) as well as broader electrochemical research including but not limited to electrocatalysis, electro-organic synthesis, analytical sensing under flow, membrane / separator screening, materials stability or compatibility studies, impurity tolerance studies, and bioelectrochemical investigations such as in vitro screening of biochemical redox activity, microbial electrochemical systems, flow-based biochemical or environmental sensing studies, and perfusion-style liquid recirculation laboratory research. Representative flow battery cycling, efficiency, and impedance data are described as non-limiting examples.

[0270] Device. System, and Method Embodiments.

[0271] Illustrative embodiment of the inventive subject matter include, but are not limited to, the following (referring to Figs. 1-17).

[0272] 1. A system for electrochemical testing comprising:

[0273] at least one flow cell 500 comprising electrodes 520 and enclosing an internal liquid volume 526, 555 separated by a membrane 530 and configured for electrochemical testing of a flow of an electrolyte, e.g., having a volume of less than or equal to 1 milliliter (m ) or less than or equal to 2 m e.g., in the system comprising the flow cell 500, pumps 420, reservoirs 430 and tubing 440, although volume can be higher in some embodiments; and

[0274] a circuit 110, 556 for supplying current or voltage to the electrodes and measuring voltage or current in response thereto.. The system of clause 1, further comprising a controller 110 operable to control application of a higher current density at lower current magnitude including (e.g, an 300 mA) driving current achieving a current density of greater than 10 A / cm23. The electrochemical test system of clause 1 or 2, wherein an active cross-sectional area of the flow cell stack is (e.g., about) 30-300 mm2, less than 30 mm2or less than 300 mm2

[0275] 4. The system of any of the clauses 1-3, further comprising an inert gas environment 200 for the flow cell. Examples of inert gas include, but are not limited to, Nitrogen or argon or other relevant non-reactive gas specific to an experiment 5. The electrochemical test system of clause 4, further comprising a vertical stacking structure configured to stack two or more electrochemical test devices or system modules to reduce bench footprint, e.g., as illustrated in Fig. 8.

[0276] 6. The system of any of the clauses 1-5, further comprising a controller 110 for controlling the current or voltage to perform a statistical analysis (device output or performance as a function of different electrolyte, cycling conditions, environmental conditions, or other test parameters).

[0277] 7. The system of any of the clauses 1-6, further comprising a plurality (e.g., an array) of the flow cells configured for multiplexed parallel operation.

[0278] 8. The system of any of the clauses 1-7, wherein the flow cell comprises a flow cell battery and the electrolyte comprises a posolyte and a negolyte used for operation of the flow cell battery.

[0279] 9. The system of any of the clauses 1-8 further comprising tubes 440 connected to each of the at least one flow cell for input and output of the electrolyte, wherein the tubes are connected to the at least one flow cell without fittings.

[0280] 10. The system of any of the clauses 1-9, further comprising a clamp 580 clamping the flow cell together using only one tightening fastener (e.g. bolt) (e.g., one clamp per flow cell if a plurality of cells).

[0281] 11. The system of any of the clauses 1-10, wherein each of the flow cells comprise a stack comprising a first block 570; a first current collector 550; a firstelectrode 520; a membrane 530; a second electrode 520; a second current collector 550 and a second block 570, wherein the stack is clamped together by the clamp 580 across the first block and the second block so that first electrode is between the first block and the membrane and the second electrode is between the membrane and the second block.

[0282] 12. The system of clause 11, wherein the electrodes are positioned with zero gap or compressed to minimize distance and therefore solution resistance between a surface of the electrodes and the membrane or separator.

[0283] 13. The system of any of the clauses 1-12, wherein the electrodes each comprise a channel defining the internal liquid volume.

[0284] 14. The system of any of the clauses 11-13, further comprising at least one first spacer or gasket 540 between the membrane and the first electrode and at least one second spacer or gasket 540 between the membrane and the second electrode, wherein the spacers or gaskets 540 each comprise an opening (e.g., having a length) defining the internal liquid volume.

[0285] 15. The system of clause 14, further comprising a graphite felt 526 or other conductive fabric material in the opening through which the electrolyte may flow.

[0286] 16. The system of any of the clauses 9-12, wherein:

[0287] the tubes 440 comprise a first tube, a second tube, a third tube, and a fourth tube,

[0288] the first electrode comprises:

[0289] a first inlet hole, wherein the first tube has an end inserted in the first inlet hole, and

[0290] a second outlet hole, wherein the second tube has an end inserted in the second outlethole;

[0291] the second electrode comprises:

[0292] a second inlet hole, wherein the third tube has an end inserted in the first inlet hole, anda second outlet hole, wherein the third tube has an end inserted in the second outlet hole; and

[0293] wherein the inlet holes and output holes 441 are positioned at opposite ends of the active surface area so that the electrolyte flows in the tubes through the inlet holes exits from the outlet holes after interacting with the electrodes in the active surface area.

[0294] 17. The system of claim 16, wherein the first and second blocks comprise plastic or compliant material interfacing with the clamp, the electrodes comprise or consist essentially of graphite, and the tubes comprise or consist of polymer (e.g., Teflon, FEP, PFA, etc).

[0295] 18. The system of any of the clauses 14-17, wherein the spacers or gaskets consist of or comprise an elastomer (e.g. Viton, FKM, FFKM, etc)

[0296] 19. The system of claims 16-18, further comprising a reference electrode 559 inserted through an opening between the inlet and the outlet through a thickness of at least one of the electrodes, so that a distal end of the reference electrode contacts with the internal liquid volume.

[0297] 20. The system of any of the clauses 1-19, wherein each of the tubes for delivering and outputting the electrolyte from the flow cell are friction fitted or interference fitted in each of the holes in the electrode, e.g, without adhesive.

[0298] 21. A flow cell 500 comprising a stack (e.g., having a volume of 1 mb or less) comprising:

[0299] a first block 570;

[0300] a first current collector 550;

[0301] a first electrode 520;

[0302] a membrane 530;

[0303] a second electrode 520;

[0304] a second current collector 550;

[0305] a first liquid volume between the first electrode and the membrane and a second liquid volume between the membrane and the second electrode;tubes 440 inserted without fittings in holes in the first electrode and the second electrode, for inputting and outputting electrolyte to the internal volumes; and

[0306] a clamp 580 clamping the stack together using one tightening fastener, e.g., at a central location.

[0307] 22. The flow cell of clause 21 dimensioned for enclosing <lml of volume of each of the first liquid volume of the posolyte and the second liquid volume of the negolyte on either / each side of the cell or system (e.g., <lml of volume of each of the posolyte and negolyte on each / either side of the cell or system, though could be larger too if desired, e.g., when the system comprises pumps, reservoirs, tubing and flow cell). In some embodiments, the volume is between 0.05ml and 0.300 ml on each side of the membrane in the flow cell..

[0308] 23. The flow cell of clause 21 or 22, wherein the tubes are friction fitted or interference fitted in the holes.

[0309] 24. The flow cell of any of the clauses 21-23 comprising a flow cell battery wherein the electrolyte comprises a posolyte in the first internal volume and a negolyte in the second internal volume.

[0310] 25. The cell of any of clauses 21-24 further comprising any of the features of clauses 2-20 or the system of any of the clauses 1-20 comprising the flow cell of any of the clauses 21-24.

[0311] 26. The system or cell of any of the clauses 1-25, further comprising at least one of the following (e.g., one or any combination of (a)-(d)

[0312] (a) (e.g., a controller operable for) independent addressing of a plurality of the flow cells, e.g., with the current or voltage;

[0313] (b) a repeatable unit cell layout of the flow cells;

[0314] (c) scalable inert gas box layouts, wherein each of the inert gas boxes contain a different one of the flow cells in an inert atmosphere;

[0315] (d) a (e.g.,. low-impedance) zero-gap assembly of each of the flow cells using a single clamp fixture / fixturing. In one or more examples a low impedance is defined as a highly-conductive interface and can be measured withimpedance spectroscopy as in Fig. 13 to confirm that the resistance (impedance) is in the single-ohm range or below.

[0316] 27. A system for electrochemical testing comprising:

[0317] at least one flow cell 500 comprising electrodes 520 and enclosing an internal liquid

[0318] volume 526, 555 separated by a membrane 530 and configured for electrochemical testing of a flow of an electrolyte, e.g., having a volume of less than 0.05ml to 0.300 ml on each side of the membrane (in some embodiments volume is between 0.05mL and 0.300 mL); and a circuit 110, 556 for supplying current or voltage to the electrodes and measuring voltage or current in response thereto.

[0319] 28. The system of clause 27, comprised the flow cell, one or more pumps, liquid reservoirs comprising the electrolyte (posolyte and negolyte) and tubing for delivery of the electrolyte from the reservoirs to the flow cell, having a total contained volume of less than 1 ml per side (e.g., per posolyte side and per negolyte side).

[0320] 29. The system of clauses 27 or 28 further comprising the flow cell of any of the clauses 1-26.

[0321] 30. The system of any of the clauses 1-29, wherein the flow cell including or excluding the clamping mechanism, has a volume of 1 mL or less. In one or more embodiments, the stack, the tubing; and the clamp have a total volume of 1 mL or less.

[0322] 31. The system of any of the clauses 1-29, wherein the volume of the electrolyte in the system is 1 mL or less or 2 mL or less, the system comprising the flow cell, reservoirs for the posolyte and the negolyte, the tubing, and one or more pumps for pumping the electrolyte to / from the reservoirs through the system.

[0323] 32. Fig. 16 illustrates a method of fabricating a flow cell, comprising, for each of a plurality of tubes being connected to the flow cell comprising a stack of components including electrodes:stretching (Block 1600) a terminal section of the tube so as to reduce a diameter of the tube along a length of the terminal section;

[0324] pulling (Block 1602) the terminal section through a hole in the electrode until the thicker unstretched portion is compressed within the hole to secure the tube in the hole;

[0325] cutting (block 1604) the thinned section as needed to leave the tube friction or interference fitted in the hole; and

[0326] clamping (Block 1606) the components together using clamp at one adjustment location.

[0327] 33. The method of clause 32 used to manufacture the cell of any of the clauses 1-31.

[0328] 34. Fig. 17 illustrates a method for testing an electrolyte or flow cell, comprising:

[0329] flowing (Block 1700) an electrolyte volume (e.g., of less than or equal to 1 mb or more than 1 mb) to a flow cell comprising electrodes, e.g., using an active surface area of less than 30 mm2or in a range of 30-300 mm2and

[0330] applying (Block 1702) a voltage across or a current to the electrodes and measuring a current or voltage in response thereto.

[0331] 35. The method of clause 34, further comprising applying a higher current density at lower current magnitude as compared to in a flow cell with a larger electrolyte volume and larger active surface area, and / or applying a voltage (e.g., of less than 1 V or a current of no more than 300 mA) to achieve a current density of greater than 10 A / cm2

[0332] 36. The method of clause 34 or 35, further comprising:

[0333] independent addressing of devices in scalable inert gas box layouts and repeatable unit cell layouts, wherein the cells have a low-impedance zero-gap design and single-clamp fixturing.

[0334] 37. A system for electrochemical testing comprising:at least one flow cell comprising electrodes and enclosing an internal liquid volume separated by a membrane and configured for electrochemical testing of a flow of an electrolyte; and

[0335] a circuit for supplying current or voltage to the electrodes and measuring voltage or current in response thereto;

[0336] connections for independent addressing of a plurality of the flow cells with the current or voltage;

[0337] a repeatable unit cell layout of the flow cells;

[0338] scalable inert gas box layouts, wherein each of the inert gas boxes contain a different one of the flow cells in an inert atmosphere; and

[0339] assembly of each of the flow cells using a single clamp fixture.

[0340] 38. The system of clause 37 including the flow cell of any of the clauses 1-31 and / or fabricated by the method of clause 32 and / or operated by the method of any of the clauses 34-36.

[0341] 39. The electrochemical test system or method of any of the clauses 1-38, further comprising a vertical stacking structure configured to stack two or more electrochemical test devices or system modules to reduce bench footprint. 40. The system or flow cell or method of any of the clauses 1-39 with "zero gap" configuration in which an electrode is positioned to minimize distance and therefore solution resistance between an electrode surface and the membrane or separator, e.g., with low impedance defined as a highly -conductive interface and can be measured with impedance spectroscopy as in Fig. 13 to confirm that the solution resistance (impedance) is in the single-ohm range (or 1 ohm) or below.

[0342] 41. The system or method of any of the clauses 1-40, wherein the system further comprises:

[0343] a first reservoir 430 for the electrolyte comprising a posolyte;

[0344] a second reservoir 430 for the electrolyte comprising the negolyte;

[0345] first tubing 440 and second tubing 440;a first pump 420 for pumping the posolyte from the first reservoir through the flow cell using the first tubing;

[0346] a second pump 420 for pumping the negolyte from the second reservoir through the flow cell using the second tubing;

[0347] an wherein the electrolyte volume flowing in the system comprises a posolyte volume and a negolyte volume, and the negolyte volume and the posolyte volume are each 1 mL or less.

[0348] 42. The system or method of any of the clauses 1-41, wherein the flow cell contains a volume of electrolyte between 0.05mL and 0.300 mL on each side of the membrane.

[0349] 43. The system or method of any of the clauses 1-41, wherein the flow cell contains a volume of posolyte between 0.05mL and 0.300 mL on the posolyte side of the membrane (including end points 0.05 mL and 0.3mL) and contains a volume of negolyte between 0.05mL and 0.300 mL on the negolyte side of the membrane (including end points 0.05 mL and 0.3mL).

[0350] References

[0351] The following references are incorporated by reference herein.

[0352] [1] U.S. Patent No. 8,980,484.

[0353] [2] https : / / www . scribner. com / products / redox-flow-cell -te sting / 857 -electrochemical-flowbench

[0354] [3] Miniaturize the Redox Flow Battery for Accelerated Materials Discovery and Development by Ruozhu Feng, Andrey V. Liyu, Soowhan Kim, Chao Zeng, Carter C. Bracken, Yangang Liang and Wei Wang Journal of The Electrochemical Society, Volume 171, Number 12, Ruozhu Feng et al 2024 J.

[0355] Electrochem. Soc. 171 120532.

[0356] [4] www.redoxino.com

[0357] [5] PCT International Publication No. WO 2025 / 050122 corresponding to PCT International Application No. PCT / US2024 / 045036 filed September 3, 2024entitled Molecular Design of electroactive species and materials processing methods in organic Redox Flow Batteries.

[0358] Conclusion

[0359] This concludes the description of the preferred embodiment of the present invention. The foregoing description of one or more embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto.

Claims

WHAT IS CLAIMED IS:

1. A system for electrochemical testing comprising:at least one flow cell comprising electrodes and enclosing an internal liquid volume separated by a membrane and configured for electrochemical testing of a flow of an electrolyte volume of less than or equal to 1 m or less than or equal to 2 m in the system; anda circuit for supplying current or voltage to the electrodes and measuring voltage or current in response thereto.

2. The system of claim 1, further comprising at least one of:(a) connections for independent addressing of a plurality of the flow cells with the current or voltage;(b) a repeatable unit cell layout of the flow cells;(c) scalable inert gas box layouts, wherein each of the inert gas boxes contain a different one of the flow cells in an inert atmosphere;(d) a zero-gap assembly of each of the flow cells using a single clamp fixture.

3. The electrochemical test system of claim 1, wherein an active cross-sectional area of the flow cell stack is about 30-300 mm2' and / or wherein the electrolyte volume of 1 mb or less or 2 mb or less is the total volume of the electrolyte in the system when the system comprises the flow cell, reservoirs for the electrolyte comprising a posolyte and a negolyte, tubing, and one or more pumps for pumping the electrolyte to / from the reservoirs through the system using the tubing.

4. The system of claim 1, wherein the system further comprises:a first reservoir for the electrolyte comprising a posolyte;a second reservoir for the electrolyte comprising the negolyte;first tubing and second tubing;a first pump for pumping the posolyte from the first reservoir through the flow cell using the first tubing;a second pump for pumping the negolyte from the second reservoir through the flow cell using the second tubing;an wherein the electrolyte volume in the system comprises a posolyte volume and a negolyte volume, and the negolyte volume and the posolyte volume are each 1 mb or less.

5. The system of claim 1, further comprising a controller operable to control application of a higher current density at lower current magnitude including a driving current achieving a current density of greater than 10 A / cm2.

6. The system of claim 1, further comprising an inert gas environment for the flow cell.

7. The electrochemical test system of claim 6, further comprising a vertical stacking structure configured to stack two or more electrochemical test devices or system modules to reduce bench footprint.

8. The system of claim 6, further comprising a controller for controlling the current or voltage to perform a statistical analysis.

9. The system of claim 6, further comprising the at least one flow cell configured for multiplexed parallel operation.

10. The system of claim 1, wherein the flow cell comprises a flow cell battery and the electrolyte comprises a posolyte and a negolyte used for operation of the flow cell battery.

11. The system of claim 1 further comprising tubes connected to the at least one flow cell for input and output of the electrolyte, wherein the tubes are connected to the at least one flow cell without fittings.

12. The system of claim 10, further comprising a clamp clamping the flow cell together using only one tightening fastener.

13. The system of claim 11, wherein the flow cell comprises a stack comprising a first block; a first current collector; a first electrode; a membrane; a second electrode; a second current collector and a second block, wherein the stack is clamped together by the clamp across the first block and the second block so that first electrode is between the first block and the membrane and the second electrode is between the membrane and the second block.

14. The system of claim 13, wherein the electrodes are positioned with zero gap to minimize distance and therefore solution resistance between a surface of the electrodes and the membrane or separator15. The system of claim 13, wherein the electrodes each comprise a channel defining the internal liquid volume.

16. The system of claim 13, further comprising at least one gasket between the membrane and the first electrode and at least one second gasket between the membrane and the second electrode, wherein the gaskets each comprise an opening defining the internal liquid volume.

17. The system of claim 16, further comprising a fabric or material in the opening through which the electrolyte may flow.

18. The system of claim 13, wherein:the tubes comprise a first tube, a second tube, a third tube, and a fourth tube, the first electrode comprises:a first inlet hole, wherein the first tube has an end inserted in the first inlet hole, anda second outlet hole, wherein the second tube has an end inserted in the second outlet hole;the second electrode comprises:a second inlet hole, wherein the third tube has an end inserted in the first inlet hole, anda second outlet hole, wherein the third tube has an end inserted in the second outlet hole; andwherein the inlet holes and output holes are positioned at opposite ends of the active surface area so that the electrolyte flows in the tubes through the inlet holes exits from the outlet holes after interacting with the electrodes in the active surface area.

19. The system of claim 13, wherein the first and second blocks comprise plastic or compliant material interfacing with the clamp, the electrodes comprise or consist essentially of graphite, and the tubes comprise or consist of polymer (e.g., Teflon).

20. The system of claim 16, wherein the gaskets consist of or comprise an elastomer.

21. The system of claim 18, further comprising a reference electrode inserted through an opening between the inlet and the outlet through a thickness of atleast one of the electrodes, so that a distal end of the reference electrode contacts with the internal liquid volume.

22. The system of claim 18, wherein each of the tubes are friction fitted or interference fitted in each of the holes without adhesive.

23. A flow cell comprising a stack comprising:a first block;a first current collector;a first electrode;a membrane;a second electrode;a second current collector;a first liquid volume between the first electrode and the membrane and a second liquid volume between the membrane and the second electrode;tubes inserted without fittings in holes in the first electrode and the second electrode, for inputting and outputting electrolyte to the internal volumes; anda clamp clamping the stack together at one fastening location or using fastening adjustment at one location.

24. The flow cell of claim 23 dimensioned for enclosing <lml of volume of each of the first liquid volume of the posolyte and the second liquid volume of the negolyte on either side of the cell or system comprising the cell.

25. The flow cell of claim 23, wherein the tubes are friction fitted or interference fitted in the holes.

26. The flow cell of claim 23 comprising a flow cell battery wherein the electrolyte comprises a posolyte in the first internal volume and a negolyte in the second internal volume.

27. A system for electrochemical testing comprising:at least one flow cell comprising electrodes and enclosing an internal liquid volume separated by a membrane and configured for electrochemical testing of a flow of an electrolyte; anda circuit for supplying current or voltage to the electrodes and measuring voltage or current in response thereto;connections for independent addressing of a plurality of the flow cells with the current or voltage;a repeatable unit cell layout of the flow cells;scalable inert gas box layouts, wherein each of the inert gas boxes contain a different one of the flow cells in an inert atmosphere; andassembly of each of the flow cells using a single clamp fixture.

28. The system of claims 2 or 14 wherein the zero gap or near zero gap resulting from the clamped or compressed stack provides a highly-conductive interface wherein the solution resistance (impedance) is in the single-ohm range or below.

29. A method of fabricating a flow cell, comprising, for each of a plurality of tubes being connected to the flow cell comprising a stack of components including electrodes:stretching a terminal section of the tube so as to reduce a diameter of the tube along a length of the terminal section;pulling the terminal section through a hole in the electrode until the thicker unstretched portion is compressed within the hole to secure the tube in the hole;cutting the thinned section as needed to leave the tube friction or interference fitted in the hole;clamping the components together using clamp at one adjustment location.

30. A method for testing an electrolyte or flow cell, comprising: flowing an electrolyte volume of less than or equal to 1 mL to a flow cell comprising electrodes; andapplying a voltage across or a current to the electrodes and measuring a current or voltage in response thereto.

31. The method of claim 30, further comprising applying a higher current density at lower current magnitude as compared to in a flow cell with a larger electrolyte volume and larger active surface area, and / or applying a voltage to achieve a current density of greater than 10 A / cm2connections using independent addressing of a plurality of the flow cells with the current or voltage in a repeatable unit cell layout of the flow cells and scalable inert gas box layouts, wherein each of the inert gas boxes contain a different one of the flow cells in an inert atmosphere; and wherein assembly of each of the flow cells uses a single clamp fixture.

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