A redox flow battery system includes an anolyte having a first ionic species in solution; a catholyte having a second ionic species in solution, where the redox flow battery system is configured to reduce the first ionic species in the anolyte and oxidize the second ionic species in the catholyte during charging; a first electrode in contact with the anolyte, where the first electrode includes channels for collection of particles of reduced metallic impurities in the anolyte; a second electrode in contact with the catholyte; and a separator separating the anolyte from the catholyte. A method of reducing metallic impurities in an anolyte of a redox flow battery system includes reducing the metallic impurities in the anolyte; collecting particles of the reduced metallic impurities; and removing the collected particles using a cleaning solution.

Embodiments provide a redox flow battery, an ion exchange membrane for use in the redox flow battery and a method for producing the ion exchanger membrane. The ion exchange membrane includes a base layer, a first hydrophobic layer, and a second hydrophobic layer. The base layer includes sulfonated poly(ether ether ketone). The base layer has a first surface and a second surface. The first hydrophobic layer includes a polydimethylsiloxane elastomer. The first hydrophobic layer is positioned on the first surface of the base layer. The second hydrophobic layer includes the polydimethylsiloxane elastomer. The second hydrophobic layer is positioned on the second surface of the base layer. The ion exchange membrane is configured to prevent cross contamination of the first electrolyte and the second electrolyte. The redox flow battery includes a first half-cell, a second half-cell, and the ion exchange membrane. The first half-cell includes a first electrolyte. The second half-cell includes a second electrolyte. The first half-cell and the second half-cell are configured to undergo a redox reaction to discharge and charge the redox flow battery.

The balancing of the state of charge of a plurality of flow battery electrolytes is better achieved by a method for a battery having a plurality of flow battery stacks in series and supplied with electrolytes from at least two stores, in which the stacks each having a plurality of cells, the method including measuring and comparing the state of charge of the electrolytes of the respective stores and registering if the states of charge differ by more than a threshold and in the case of the state of the charge difference threshold being exceeded: controlling the number of cells in the series connection of the stacks whereby the less charged electrolytes discharge through fewer cells than the more charged electrolytes and/or controlling the number of cells in the series connection of the stacks whereby the less charged electrolytes are charged through more cells than the more charged electrolytes.

A fuel cell system includes: a fuel cell including an MEA including an electrolyte membrane and anode and cathode catalyst layers sandwiching the electrolyte membrane; an impedance measuring device measuring AC impedance of the fuel cell when AC voltage is applied to the fuel cell; an impedance acquisition unit configured to obtain a first imaginary part value of the AC impedance measured when AC voltage with a fixed frequency satisfying Fixed frequency [Hz]×(Thickness of the electrolyte membrane [μm]).sup.2≤500 [Hz×μm.sup.2] is applied in a state where a relative humidity of the MEA is 20% or greater, and a fuel gas is present and an oxidant gas is absent in the anode and cathode catalyst layers; and a metal ion estimation unit configured to estimate a content of metal ions in the electrolyte membrane based on the first imaginary part value of the AC impedance.

Methods and systems are provided for a rebalancing reactor of a flow battery system. In one example, a pH of a battery electrolyte may be maintained by the rebalancing reactor by applying a negative potential to a catalyst bed of the rebalancing reactor. A performance of the rebalancing reactor may further be maintained by treating the catalyst bed with deionized water.

A method for a redox flow battery may include, interrupting cycling of the redox flow battery, including charging the redox flow battery to a threshold charge condition, draining positive and negative electrolyte from the redox flow battery, circulating a wash solution through the redox flow battery, and returning the positive and negative electrolyte to the redox flow battery, and resuming cycling of the redox flow battery. In this way, contamination of the redox flow battery system can be reduced, thereby prolonging the life and increasing performance of the redox flow battery system.

A state of charge indicator arrangement for a redox flow battery system having a reference cell arrangement for measuring potential difference between a positive electrolyte and a negative electrolyte of the flow battery and an auxiliary reference electrolyte arrangement is provided. The indicator includes a discrete auxiliary electrolyte reservoir for housing a redox electrode in association with a reference electrolyte of known composition comparable to the desired or initial composition of the flow battery electrolyte for which it provides a reference, a means of measuring the potential difference between the auxiliary reference electrolyte and the electrolyte of the reference cell arrangement and an ionic pathway conduit linking the auxiliary reference electrolyte reservoir with the electrolyte of the reference cell arrangement, which is configured for low fluid diffusion rate.

A redox flow battery includes a redox flow cell, a supply/storage system external of the redox flow cell, and a controller. The supply/storage system includes first and second electrolytes for circulation through the redox flow cell. The first electrolyte is a liquid electrolyte having electrochemically active species with multiple, reversible oxidation states. The electrochemically active species can form a solid precipitate blockage in the redox flow cell. The controller is configured to identify whether there is the solid precipitate blockage in the redox flow cell and, if so, initiate a regeneration mode that reduces the oxidation state of the electrochemically active species in the liquid electrolyte to dissolve, in situ, the solid precipitate blockage.

Embodiments provide a redox flow battery, an ion exchange membrane for use in the redox flow battery and a method for producing the ion exchanger membrane. The ion exchange membrane includes a base layer, a first hydrophobic layer, and a second hydrophobic layer. The base layer includes sulfonated poly(ether ether ketone). The base layer has a first surface and a second surface. The first hydrophobic layer includes a polydimethylsiloxane elastomer. The first hydrophobic layer is positioned on the first surface of the base layer. The second hydrophobic layer includes the polydimethylsiloxane elastomer. The second hydrophobic layer is positioned on the second surface of the base layer. The ion exchange membrane is configured to prevent cross contamination of the first electrolyte and the second electrolyte. The redox flow battery includes a first half-cell, a second half-cell, and the ion exchange membrane. The first half-cell includes a first electrolyte. The second half-cell includes a second electrolyte. The first half-cell and the second half-cell are configured to undergo a redox reaction to discharge and charge the redox flow battery.

A method is provided for restoring an electrolyte of vanadium (V) redox flow battery (VRFB). Electrolyte data of an original system are analyzed in advance. A reusable positive electrode is further equipped with a V electrolyte. A reductant for a stack of VRFB is used in coordination as an electrolysis device. After a long-term reaction with a VRFB having a high valence (greater than 3.5), an electrolyte at the positive electrode is directed out to a negative electrode of the electrolysis device; and, then, electrolysis is processed after accurate calculation. In the end, the internal fluid balancing method of the original system is combined. Thus, a harmless and quick valence restoration is processed for the electrolyte of the original system, which is a final resort for the restoration of V electrolyte.