Balancing and measurement device for redox flow batteries

Abstract

The present invention relates to a device for electrochemical balancing of electrolytes of a redox flow battery, a redox flow battery system device, methods using thereof and uses thereof.

Description

[0001] Balancing and measurement device for redox flow batteries

[0002] Technical Field

[0003] The present disclosure relates to a device for the electrochemical balancing of the electrolytes of a redox flow battery, measuring state of charge, measuring copper content in the electrolytes, and capable of correcting for electrolyte volume discrepancies with the device being especially applicable for copper based redox flow batteries.

[0004] Background

[0005] Due to both environmental and geopolitical concerns a significant shift in the energy generation market has occurred to move energy generation from fossil fuel-based sources to renewable energy generators such as photovoltaics and wind power. However, for the integration of intermittent renewable energy sources into the existing power grid sufficient energy storage is required to firm both the energy output from the renewable sources and to stabilize the energy grid. With the energy storage performing functions such as system peak shaving, frequency regulation, price arbitrage, and renewable firming, and can serve additional needs such as backup power systems. With frequency regulation and price arbitrage being the two largest use cases for utility scale energy storage, however increasingly systems have been performing one or more application.

[0006] Redox flow batteries are highly suited to provide the capacities need for further integration of renewable energy storage due to their high-power rating, large capacity, fast response time, and their long-term operability compared to competing energy storage technologies. Redox flow batteries work by circulating two separate electrolytes through a cell divided by a separator and or ion exchange membrane. During the charging process one of the active species in the negolyte becomes reduced lowering the oxidation state of the active species, and the active species in the posilyte become oxidized during the process. Charging is typically achieved by applying external power either from the grid or directly from the energy generation source. During discharge the oxidation state of the active species in the negolyte oxidize again, and the active species in the posilyte become reduced thereby allowing for energy to be extract from the system during discharge.

[0007] With the aqueous all copper redox flow battery being one of the chemistries used in redox flow batteries. In the copper redox flow battery Cu(l) is used as the 0% state of charge active species in both the negolyte and posilyte. During the charge process Cu(l) in the negolyte is reduced to metallic copper and deposited onto a conductive substrate and or electrode, meanwhile the Cu(l) present in the posilyte is oxidized to Cu(ll) on the conductive substrate and or electrode. As with most flow batteries the copper flow battery suffers from gradual capacity loss during operation for extended periods. For the copper redox flow battery this capacity decay comes from the separator and or ion exchange membrane allowing for the transport of Cu(l) / Cu(ll) species from whichever electrolyte has the highest concentration of the species to the electrolyte with the lower concentration of this species through osmotic transfer.

[0008] In the case of the copper battery this is further exacerbated through the comproportionation reaction wherein when Cu(ll) comes into contact with copper deposited during the charging phase in the negolyte resulting in the formation of 2Cu(l) ions effective reducing the discharge capacity and resulting in a semipermanent capacity loss unless treated. And this imbalance results in a lack of available copper ions during the charge process, resulting in lower charge capacity during each subsequent cycle. Tracking of how many copper ions are present in which electrolyte is difficult and often involves expensive equipment such as ultraviolet measurement devices to determine the copper content of the posilyte and negolyte. Operation of the system is further complicated as one cannot obtain real time state of charge values from the system while operation is underway as typically the open circuit voltage is needed to determine the state of charge, and this would in essence pause operation of the system to determine the open circuit voltage and the state of charge.

[0009] Thus, there is a need for a device which can externally measure the state of charge of the system without interruption. Additionally, a device is needed which can to some extent determine the copper concentrations in both the posilyte and negolyte and perform necessary operation to rebalance the copper content of both electrolyte to the desired quantity. As by correcting the copper content in both electrolytes the capacity of the system can be recovered and a method is needed to do this in a continuous fashion without interruption of the main system. Finally, there exists a need for a device which is capable of correcting for electrolyte volume shifts over time due to osmotic effects, without causing the main redox flow battery system to be halted. Summary

[0010] Rebalancing

[0011] The object of the present disclosure is to provide an easy and continuous method for the electrochemical rebalancing electrolytes employed in redox flow batteries which use copper as the main active species.

[0012] A further object of the present disclosure is to provide a method for the continuous electrochemical rebalancing of the electrolytes employed in a redox flow battery which uses copper as the main active species without affecting the primary function of said redox flow battery.

[0013] A still further object of the present disclosure is to provide a method for the continuous electrochemical rebalancing of the electrolytes employed in a redox flow battery which uses copper as the main active species with minimal energy input.

[0014] A still further object of the present disclosure is to provide a method for the continuous electrochemical rebalancing of the electrolytes employed in a redox flow battery which uses copper as the main active species without the generation of hydrogen, oxygen, or other noxious gasses.

[0015] A still further object of the present disclosure is to provide a method for the continuous electrochemical rebalancing of the electrolytes employed in a redox flow battery which uses copper as the main active species through which the capacity of the battery can be continuously maintained at its highest operating level.

[0016] A still further object of the present disclosure is to provide a method for the continuous electrochemical rebalancing of the electrolytes employed in a redox flow battery which uses copper as the main active species which can be scaled by repeating multiple half-cells for large scale rebalancing.

[0017] In a preferred embodiment the device the negolyte which contains a mixture between Cu(l) and Cu(ll) is circulated into the device and through the application of an applied voltage the copper undergoes an electrochemical reaction to metallic copper and deposits on the electrode substrate. For the counter reaction the posilyte which contains a mixture between Cu(l) and Cu(ll) a positive potential is applied, and the oxidation state changes to Cu(ll) of the majority of the species. The valves are then arranged in such a fashion where the posilyte is circulated through the chamber in which the deposition of copper has occurred on the electrode substrate. When the Cu(ll) comes into contact with the copper deposited on the electrode substrate through a well-known established reaction known as a comproportionation reaction, also referred to as the copper etching process, occurs resulting in the dissolution of the metallic copper and the Cu(ll) becoming reduced to a Cu(l) states thereby making 2Cu(l). This results in the transference of dissolved copper species from the negolyte to the posilyte. Thereby the benefit can be achieved of transferring copper from the negolyte to the posilyte to recover capacity lost through well- established capacity loss mechanisms. After performing the aforementioned described the process the capacity of the system can recovered to its initial state or adjusted to an intended state.

[0018] In a different embodiment the device has the configuration depicted in Figure 1A, where the posilyte which contains a mixture between Cu(l) and Cu(ll) is circulated into the device and through the application of an applied voltage the copper undergoes an electrochemical reaction to metallic copper and deposits on the electrode substrate. For the counter reaction the negolyte which contains a mixture between Cu(l) and Cu(ll) a positive potential is applied, and the oxidation state changes to Cu(ll) of the majority of the species. The valves are then arranged in such a fashion where the negolyte is circulated through the chamber in which the deposition of copper has occurred on the electrode substrate. When the Cu(ll) comes into contact with the copper deposited on the electrode substrate through a well-known established reaction known as a comproportionation reaction, also referred to as the copper etching process, occurs resulting in the dissolution of the metallic copper and the Cu(ll) becoming reduced to a Cu(l) states thereby making 2Cu(l). This results in the transference of dissolved copper species from the posilyte to the negolyte. Thereby the benefit can be achieved of transferring copper from the posilyte to the negolyte to recover capacity lost through well-established capacity loss mechanisms. After performing the aforementioned described the process the capacity of the system can recovered to its initial state or adjusted to an intended state.

[0019] State of charge determination

[0020] A further object of the present disclosure is to provide an easy method for determining the relative state of charge of a copper based redox flow battery through the use of an external cell. A yet further object of the present disclosure is to provide an easy method for determining the relative amount of copper species present in both the posilyte and negolyte.

[0021] In a different embodiment the negolyte is fed, containing a mixture of Cu(l) and Cu(ll), into one of the half cells of the device proposed by the present disclosure where a negative potential is applied resulting the electrodeposition of the copper species on the electrode substrate. To the second half-cell of the device proposed by the present disclosure the posilyte is fed, containing a mixture of Cu(l) and Cu(ll), where a positive potential is applied transforming some or all of the species to Cu(ll). After an initial thin layer is deposited on the electrode substrate no voltage is applied to any of the two half-cells and the open circuit voltage of the device proposed by the present disclosure is measured, i.e., no current flow is observed. This open circuit voltage can then be used to determine the state of charge of the electrolytes. In a certain embodiment the posilyte is fed, containing a mixture of Cu(l) and Cu(ll), into one of the half cells of the device proposed by the present disclosure where a negative potential is applied resulting the electrodeposition of the copper species on the electrode substrate. To the second half-cell of the device proposed by the present disclosure the negolyte is fed, containing a mixture of Cu(l) and Cu(ll), where a positive potential is applied transforming some or all of the species to Cu(ll). After an initial thin layer is deposited on the electrode substrate no voltage is applied to any of the two half-cells and the open circuit voltage of the device proposed by the present disclosure is measured, i.e., no current flow is observed. This open circuit voltage can then be used to determine the amount of Cu(ll) species in the negolyte using established electrochemical formulae such as the Nernst equation.

[0022] In a different embodiment the negolyte is fed, containing a mixture of Cu(l) and Cu(ll), into one of the half cells of the device proposed by the present disclosure where a negative potential is applied resulting the electrodeposition of the copper species on the electrode substrate. To the second half-cell of the device proposed by the present disclosure the posilyte is fed, containing a mixture of Cu(l) and Cu(ll), where a positive potential is applied transforming some or all of the species to Cu(ll). After an initial thin layer is deposited on the electrode substrate no voltage is applied to any of the two half-cells and the open circuit voltage of the device proposed by the present disclosure is measured, i.e., no current flow is observed. This open circuit voltage can then be used to determine the amount of Cu(ll) species in the posilyte using established electrochemical formulae such as the Nernst equation.

[0023] Electrolyte volume correction

[0024] A yet further object of the present disclosure is to provide a simple method for maintaining the electrolyte volumes of the electrolytes employed by redox flow battery which uses copper as the main active species.

[0025] In a different embodiment the device proposed in the current invention disclosure the weight of both the posilyte and negolyte containment tanks can be determined through appropriate means, or volume determination through appropriate means. This information can then be used by using the device proposed in the current invention disclosure and its associated valves to move measured amounts of the posilyte to the negolyte, or from the negolyte to the posilyte dependent on the preferred negolyte to posilyte ratio for the operation of a redox flow battery which uses copper as its main active species.

[0026] Brief description of the drawings

[0027] Figure 1 is a schematic view showing a device that can rebalance the electrolytes of a redox flow battery which uses copper as the main active species.

[0028] Figure 2. Electrochemical energy storage employing copper as the active species Figure 3. Benefits of Copper electrochemical energy storage

[0029] Figure 4. Competitive solutions and performance comparison of the various battery systems

[0030] Figure 5. A prototype according to the invention

[0031] Detailed description

[0032] In one aspect is provided a device for electrochemical balancing of electrolytes of a redox flow battery, wherein the battery comprises a first half-cell and a second half-cell separated by a separator (12), wherein the device comprises: a first tank (1 ) for receiving an electrolyte; a second tank (6) for receiving an electrolyte; a plurality of connecting pipes (16, 17, 18, 19, 20, 21 , 22, 23, 24, 25, 26, 27) for passing electrolyte therethrough; a first pump (2) and a second pump (5) for pumping electrolyte, wherein the first pump (2) being configured to pump electrolyte between the first tank( 1 ), the first half-cell, the second half-cell, and / or the second tank (6), and wherein the second pump (5) being configured to pump electrolyte between the second tank (6), the second half-cell, the first half-cell, and / or the first tank (1 ); and four three-way valves (3, 4, 7, 8) configured to provide fluid connections between the first tank (1), the second tank (6), and / or the redox flow battery together with the plurality of connecting pipes and the first pump and / or the second pump.

[0033] Additionally, or alternatively, the four three-way valves comprise a first three-way valve (3), a second three-way valve (4), a third three-way valve (8), and a fourth three-way valve (7), wherein the first three-way valve (3) being configured to pass electrolyte between the first tank (1) and / or the first half-cell and / or the second tank (6), the second three-way valve (4) being configured to pass electrolyte between the first tank (1 ) and / or the second half-cell and / or the second tank (6), the third three-way valve (8) being configured to pass electrolyte between the first tank (1) and / or the first half-cell and / or the second tank (6), and the fourth three-way valve (7) being configured to pass electrolyte between the first tank (1 ) and / or the second half-cell and / or the second tank (6).

[0034] Additionally, or alternatively, the first pump (2) being configured to pump electrolyte through the first three-way valve (3) from the first tank (1 ), at least two connecting pipes (17, 18) of the plurality of connecting pipes and the first half-cell, and being configured to pump electrolyte through the second three-way valve (4) from the first tank (1 ), at least two connecting pipes (16, 21) of the plurality of connecting pipes and the second half-cell; and the second pump (5) being configured to pump electrolyte through the second three-way valve (4) from the second tank (6), at least two connecting pipes (19, 21 ) of the plurality of connecting pipes and the second half-cell, and being configured to pump electrolyte through the first three-way valve (3) from the second tank (6), at least two connecting pipes (18, 20) of the plurality of connecting pipes and the first half-cell; wherein the first half-cell being configured to be in fluid connection through the third three- way valve (8) via connecting pipes (27, 22) of the plurality of connecting pipes into the first tank (1 ) and through the third three-way valve (8) via connecting pipes (27, 25) of the plurality of connecting pipes into the second tank (6), and wherein the second half-cell being configured to be in fluid connection through the fourth three- way valve (7) via connecting pipes (26, 24) of the plurality of connecting pipes into the second tank (6) and through the fourth three-way valve (7) via connecting pipes (26, 23) of the plurality of connecting pipes into the first tank (1 ).

[0035] Additionally, or alternatively, the first flow-cell comprises a first electrode (10), an electrically conductive material (11 ), and a non-conductive spacer (9); the second flow-cell comprises a second electrode (13), an electrically conductive material (15), and a non-conductive spacer (14).

[0036] Additionally, or alternatively, the device further comprises means for applying a voltage to the redox flow battery.

[0037] Additionally, or alternatively, the device further comprises means for applying a voltage to the first electrode (10) and the second electrode (13).

[0038] Additionally, or alternatively, the device further comprises means for measuring the relative electroconducting species, such as the copper species, content in the electrolytes.

[0039] Additionally, or alternatively, the means for measuring the relative electroconducting species is means for determing the weight of the first tank and / or the second tank.

[0040] Additionally, or alternatively, the means for measuring the relative electroconducting species is means for determing the volume of the electrolyte in the first tank and / or electrolyte in the second tank.

[0041] Additionally, or alternatively, the electrolyte comprises or consists copper species, zink species, bromine species, and / or iron species, preferably the electrolyte comprises or consists copper species.

[0042] Additionally, or alternatively, the redox flow battery is a copper based redox flow battery.

[0043] In one aspect is provided a redox flow battery system comprising: redox flow battery comprising a first half-cell for receiving an electrolyte and comprising a first electrode (10), an electrically conductive material (11 ), and a non-conductive spacer (9); and a second half-cell for receiving an electrolyte and comprising a second electrode (13), an electrically conductive material (15), and a non-conductive spacer (14), wherein the first half-cell and the second half-cell are separated by a separator (12); and the device as defined in the present disclosure.

[0044] Additionally, or alternatively, the device and / or the redox flow battery further comprises electrolyte, such as in the first half-cell and the second half-cell and / or in the first tank and the second tank.

[0045] Additionally, or alternatively, the system further comprises an electric power source deatachable attached to the system for applying a voltage to the redox flow battery, preferably to the first electrode and the second electrode.

[0046] In one aspect is provided a method for determining the relative state of charge of a redox flow battery, wherein the method comprises: i) providing a redox flow battery system as defined in the present disclosure, wherein the device being configured to be in fluid connection with the redox flow battery; ii) providing electrolytes to the redox flow battery system, preferably to the first tank and the second tank of the device; iii) providing, preferably by pumping by the first and the second pump, electrolyte from the first tank to or through the first half-cell and electrolyte from the second tank to or through the second half-cell, or electrolyte from the second tank to or through the first half-cell and electrolyte from the first tank to or through the second half-cell; iv) applying a negative potential to the first electrode and a positive potential to the second electrode, or a positive potential to the first electrode and a negative potential to the second electrode, thereby resulting in the reduction of electroconducting species of the electrolyte in the half-cell comprising the electrode applied with a negative potential and thereby the electrodeposition of electroconducting species, preferably metallic copper species, on the electrically conductive material comprised in the half-cell comprising the electrode applied with a negative potential , and oxidating at least a part of electroconducting species of the electrolyte in the half-cell comprising the electrode applied with a negative potential , preferably oxidating electroconducting species of the electrolyte in the half-cell comprising the electrode applied with a negative potential to Cu(ll), on the electrically conductive material comprised in the half-cell comprising the electrode applied with a negative potential; v) stopping applying voltage to the first electrode and the second electrode; and vi) measuring the open circuit voltage of the device, thereby determining the state of charge of the electrolyte.

[0047] Additionally, or alternatively, in iii), arranging the three-way valves such that only the second tank is in fluid connection with the first half-cell and providing, preferably by pumping by the second pump, electrolyte from the second tank through the first half-cell, and arranging the three-way valves such that only the first tank is in fluid connection with the second half-cell and providing, preferably by pumping by the first pump, electrolyte from the first tank through the second half-cell; and in iv), applying a negative potential to the first electrode, thereby resulting in the reduction of electroconducting species of the electrolyte in the first half-cell and thereby the electrodeposition of electroconducting species, preferably metallic copper species, on the electrically conductive material (11 ); and applying a positive potential to the second electrode, thereby oxidating at least a part of electroconducting species of the electrolyte in the second half-cell, preferably oxidating electroconducting species of the electrolyte in the second half-cell to Cu(ll), on the electrically conductive material (15), or applying a negative potential to the second electrode, thereby resulting in the reduction of electroconducting species of the electrolyte in the second half-cell and thereby the electrodeposition of electroconducting species, preferably metallic copper species, on the electrically conductive material (15); and applying a positive potential to the first electrode, thereby oxidating at least a part of electroconducting species of the electrolyte in the first half-cell, preferably oxidating electroconducting species of the electrolyte in the first half-cell to Cu(ll), on the electrically conductive material (11 ).

[0048] Additionally, or alternatively, in iii), arranging the three-way valves such that only the first tank is in fluid connection with the first half-cell and providing, preferably by pumping by the first pump, electrolyte from the first tank through the first half-cell, and arranging the three-way valves such that only the second tank is in fluid connection with the second half-cell and providing, preferably by pumping by the second pump, electrolyte from the second tank through the second half-cell; and, in iv), applying a negative potential to the first electrode, thereby resulting in the reduction of electroconducting species of the electrolyte in the first half-cell and thereby the electrodeposition of electroconducting species, preferably metallic copper species, on the electrically conductive material (11 ); and applying a positive potential to the second electrode, thereby oxidating at least a part of electroconducting species of the electrolyte in the second half-cell , preferably oxidating electroconducting species of the electrolyte in the second half-cell to Cu(ll), on the electrically conductive material (15), or applying a negative potential to the second electrode, thereby resulting in the reduction of electroconducting species of the electrolyte in the second half-cell and thereby the electrodeposition of electroconducting species, preferably metallic copper species, on the electrically conductive material (15); and applying a positive potential to the first electrode, thereby oxidating at least a part of electroconducting species of the electrolyte in the first half-cell , preferably oxidating electroconducting species of the electrolyte in the first half-cell to Cu(ll), on the electrically conductive material (11 ).

[0049] Additionally, or alternatively, in iii), arranging the three-way valves such that electrolyte is provided from the first tank through the first half-cell and back to the first tank, and electrolyte from the second tank through the second half-cell and back to the second tank, or electrolyte from the second tank through the first half-cell and back to the second tank, and electrolytes from the first tank through the second half-cell and back to the first tank.

[0050] Additionally, or alternatively, iv) further comprises ending providing electrolyte from the first tank through the first half-cell, preferably by ending pumping by the first pump and / or arranging the three-way valves such that only the second tank is in fluid connection with the second half-cell and the first tank is not in fluid connection with the first half-cell; and providing electrolyte from the second tank through the second half-cell; and v) stopping applying voltage to the first electrode and the second electrode when essentially all of the electrolyte captured within the first half-cell is entirely oxidized, preferably the electrolyte comprising Cu(l) and Cu(ll) captured within the first halfcell is entirely oxidized to Cu(ll).

[0051] Additionally, or alternatively, iv) further comprises ending providing electrolyte from the second tank through the second half-cell, preferably by ending pumping by the second pump and / or arranging the three-way valves such that only the first tank is in fluid connection with the first half-cell and the second tank is not in fluid connection with the second half-cell; and providing electrolyte from the first tank through the first half-cell; and v) stopping applying voltage to the first electrode and the second electrode when essentially all of the electrolyte captured within the second half-cell is entirely oxidized, preferably the electrolyte comprising Cu(l) and Cu(ll) captured within the second half-cell is entirely oxidized to Cu(ll).

[0052] In one aspect is provided a method for electrochemical rebalancing of electrolytes of a redox flow battery, wherein the method comprises: i) providing a redox flow battery system as defined in the present disclosure, wherein the device being configured to be in fluid connection with the redox flow battery; ii) providing electrolytes to the redox flow battery system, preferably to the first tank and the second tank of the device; iii) providing, preferably by pumping by the first and the second pump, electrolyte from the first tank to the first half-cell and electrolyte from the second tank to the second half-cell, or electrolyte from the second tank to the first half-cell and electrolyte from the first tank to the second half-cell; iv) applying a negative potential to the first electrode and a positive potential to the second electrode, or a positive potential to the first electrode and a negative potential to the second electrode, thereby resulting in the reduction of electroconducting species of the electrolyte in the half-cell comprising the electrode applied with a negative potential and thereby the electrodeposition of electroconducting species, preferably metallic copper species, on the electrically conductive material comprised in the half-cell comprising the electrode applied with a negative potential, and oxidating at least a part of electroconducting species of the electrolyte in the half-cell comprising the electrode applied with a negative potential, preferably oxidating electroconducting species of the electrolyte in the half-cell comprising the electrode applied with a negative potential to Cu(ll), on the electrically conductive material comprised in the half-cell comprising the electrode applied with a negative potential; v) stopping applying voltage to the first electrode and the second electrode; and viii) arranging the three-way valves such that only the first tank is in fluid connection with the first half-cell and providing, preferably by pumping by the first pump, electrolyte from the first tank through the first half-cell, thereby dissoluting the electrodeposited electroconducting species, preferably metallic copper, and reducing Cu(ll) to Cu(l), or arranging the three-way valves such that only the second tank is in fluid connection with the first half-cell and providing, preferably by pumping by the second pump, electrolyte from the second tank through the first half-cell, thereby dissoluting the electrodeposited electroconducting species, preferably metallic copper, and reducing Cu(ll) to Cu(l).

[0053] Additionally, or alternatively, the electrolyte or the electrolytes compise(s) or contain(s) electroconducting species or a plurality of electroconducting species, such as copper species. Examples of copper species my include, but are not limited to, Cu(l), Cu(ll), and metallic copper.

[0054] Additionally, or alternatively, the method further comprises: ix) measuring the relative electroconducting species, such as the copper species, content in the electrolytes, thereby obtaining a result value.

[0055] Additionally, or alternatively, in ix), the measuring the relative electroconducting species is determing the weight of the first tank and / or the second tank, thereby obtaining one or more result values.

[0056] Additionally, or alternatively, in ix), the measuring the relative electroconducting species is determing the volume of electrolyte in the first tank and / or electrolyte in the second tank, thereby obtaining one or more result values. Additionally, or alternatively, the metod further comprises: x) comparing the obtained result value(s) from the measuring with a predetermined value / predetermined values; xi) providing electrolytes from the first tank to the second tank if the obtained result value(s) from the measuring is / are equal or lower than the predetermined value(s), or providing electrolytes from the second tank to the first tank if the obtained result value(s) from the measuring is / are higher than the predetermined value(s).

[0057] Additionally, or alternatively, the method as defined in the present disclosure for continuous electrochemical rebalancing of electrolytes of a redox flow battery, wherein the metod comprises the sequence of iii) to xi) two or more times.

[0058] In one aspect is provided a method for rebalancing of electrolytes of a redox flow battery system, wherein the method comprises: i) providing a redox flow battery system as defined in the present disclosure, wherein the device being configured to be in fluid connection with the redox flow battery; ii) providing electrolytes to the redox flow battery system, preferably to the first tank and the second tank of the device; iii) providing, preferably by pumping by the first pump, electrolyte from the first tank through the first half-cell or the second half-cell to the second tank, or providing, preferably by pumping by the second pump, electrolyte from the second tank through the second half-cell or the first-half cell to the first tank.

[0059] Additionally, or alternatively, in iii), arranging the three-way valves such that the first tank is in fluid connection with the second tank only via the first first three-way valve (3), the first half-cell, the third three-way valve (8), and connecting pipes (17, 20, 27, 25), or such that the first tank is in fluid connection with the second tank only via the second three-way valve (4), the second half-cell, the fourth three-way valve (7), and connecting pipes (16, 21 , 26, 24).

[0060] In one aspect is provided a use of a device as defined in in the present disclosure or a redox flow battery system as defined in the present disclosure for determining the relative state of charge of a redox flow battery, preferably a copper based redox flow battery, for determining the relative amount of electroconducting species, such as the copper species, content in the electrolytes, for maintaining the electrolyte volumes of the electrolytes employed by redox flow battery, preferably which uses copper as the main active species, and for electrochemical balancing, preferably continuous electrochemical balancing, of electrolytes.

[0061] In one aspect is provided a use of a redox flow battery system device as defined in the present disclosure for storing energy for time-shift, load balancing, and backup power systems.

[0062] Rebalancing

[0063] Figure 1 is a schematic view of the preferred embodiment of the invention for the electrolyte rebalancing of the electrolytes used in a redox flow battery which uses copper as the main active species, however, the present invention is limited to this description. Which consist of an electrode 10 to which a positive or negative potential can be applied, and another electrode 13 to which a positive or negative potential can be applied, separated by a separator 12, which can be either a porous or non-porous separator but not limited to these two options. Both the posilyte tank 1 , and the negolyte tank 6 are connected to a pump 2 and pump 5 respectively. The outlets for pump 2 can be configured through the three-way valve 3 or the three-way valve 4 to be pumped into either the chamber containing electrode 10 or electrode 13. The outputs from pump 2 can be routed either back to the posilyte containment tank 1 , or through the use of three-way valve 8 or three-way valve 7 to the negolyte tank 6. Similarly, the negolyte tank 6 electrolyte can be pumped by pump 5 through the compartment containing electrode 10 or electrode 13 through switching of the three-way valve 3 or the three-way valve 4 respectively. The outputs can then either be routed back to the negolyte tank 6 through the switching of the three-way valve 7 or through switching of the three-way valve 8. Inside each of the half cells an electrically conductive material 11 and 15 is present which can consist of metallic foams or carbon-based foams to form a reaction surface for the electrochemical reactions to occur. The membrane 12 is separated from the electrically conductive material 11 by a non-conductive spacer 9, which can consist of material such as reverse osmosis spacers but not limited to only this material. The membrane 12 is additionally separated from the conductive material 15 by a non-conductive spacer 14, which can consist of a material such as reverse osmosis spacers but not limited to only this material.

[0064] In a further embodiment the posilyte from the posilyte tank 1 is pumped through pipe 17 by connecting pipe 17 to pipe 20 through the use of three-way valve 3 into the chamber containing electrically conductive material 11 . By apply a negative voltage to electrode 10, and thus having a negative voltage on electrically conductive material 11 any Cu(l) or Cu(ll) in contact with electrically conductive material 11 will be reduced and deposit on electrically conductive material 11 in the form of metallic copper. The posilyte then exits the half-cell through pipe 27 and by connecting pipe 27 to pipe 22 through the use of three-way valve 8 is recirculated to posilyte tank 1 . While this process is occurring the negolyte from tank 6 is circulated through the use of pump 5 into pipe 19 which is connected to pipe 21 through three-way valve 4 into the half-cell which contains electrically conductive material 15. A subsequent positive voltage is applied to electrode 13 thereby resulting in a positive voltage being applied to electrically conductive material 15. The negolyte being pumped into the system containing a mixture of Cu(l) and Cu(ll) species results in the Cu(l) species being oxidized to Cu(ll) through the positive voltage being applied to electrically conductive material 15. The negolyte now containing Cu(ll) species is fed back into the negolyte tank 6 through using the three-way valve 7 to connect pipe 26 and pipe 24. At this point the negolyte contains excess Cu(ll) ions in the negolyte tank 6, and some of the copper present in the posilyte is deposited on the electrically conductive material 11 . For the next steps pump 2 and pump 5 are disabled, three-way valve 4 is closed, and three-way valve 7 is closed. The negolyte containing an excess of Cu(ll) ions is then circulated by reactivating pump 5 through pipe 18 into pipe 20 using three-way valve 3, this allows for the excess Cu(ll) ions to come into contact with the copper deposited on electrically conductive material 11 , which then react using the well established comproportionation reaction of copper where Cu(ll) reacts with metallic Cu to form 2Cu(l). The negolyte is then recirculated through pipe 27 and pipe 25 through the use of three-way valve 8 back to negolyte tank 6. Resulting in effective and low energy cost transfer of copper ions from the posilyte tank 1 to the negolyte tank 6 through electrochemical means.

[0065] In a further embodiment the posilyte from the posilyte tank 1 is pumped through pipe 17 by connecting pipe 17 to pipe 20 through the use of three-way valve 3 into the chamber containing electrically conductive material 11 . By apply a positive voltage to electrode 10, and thus having a positive voltage on electrically conductive material 11 any Cu(l) in the posilyte will be in contact with electrically conductive material 11 and become oxidized by electrically conductive material 11 to Cu(ll). The posilyte then exits the half-cell through pipe 27 and by connecting pipe 27 to pipe 22 through the use of three-way valve 8 is recirculated to posilyte tank 1 . While this process is occurring the negolyte from tank 6 is circulated through the use of pump 5 into pipe 19 which is connected to pipe 21 through three-way valve 21 into the half-cell which contains electrically conductive material 15. A subsequent negative voltage is applied to electrode 13 thereby resulting in a negative voltage being applied to electrically conductive material 15. The negolyte being pumped into the system containing a mixture of Cu(l) and Cu(ll) species results in the Cu(l) and Cu(ll) species being reduced to metallic copper through the negative voltage being applied to electrically conductive material 15 and will deposit on electrically conductive material 15. The negolyte now containing a reduced amount of copper species is fed back into the negolyte tank 6 through using the three-way valve 7 to connect pipe 26 and pipe 24. At this point the posilyte contains excess Cu(ll) ions in posilyte tank 1 , and some of the copper from the negolyte is deposited on the electrically conductive material 11 . For the next steps pump 2 and pump 5 are disabled, three-way valve 3 and three-way valve 8 are closed. The posilyte now containing excess Cu(ll) species is circulated using pump 2 through pipe 16 into pipe 21 through switching of three-way valve 4 over electrically conductive material 15. The excess Cu(ll) species in the posilyte then reacts with the copper deposited on electrically conductive material 15 from the negolyte through the well established comproportionation reaction to form 2Cu(l) species. The posilyte now containing an increase in the amount of copper is circulated back to the posilyte tank through pipe 26 and pipe 23 through switching of three-way valve 7. Resulting in effective and low energy cost transfer of copper ions from the negolyte in tank 6 to the posilyte in tank 1 .

[0066] State of Charge Estimation

[0067] In yet a further embodiment the posilyte from tank 1 is circulated through pipe 17 into pipe 20 through the use of three-way valve 3 into the half cell containing electrically conductive material 11 through the use of pump 2. With a positive potential being applied to electrode 10 resulting in a positive voltage on electrically conductive material 11 , the posilyte which contains a mixture of Cu(l), and Cu(ll) is then subsequently oxidized to Cu(ll) and is recirculated to posilyte tank 1 through pipe 27 and pipe 22 through the use of three-way valve 8. In the same fashion the negolyte from tank 6 is circulated through pipe 19 and pipe 21 through the use of three-way valve 4 into the half-cell containing electrically conductive material 14 using pump 5. With a negative potential being applied to electrode 13 resulting in a negative potential on electrically conductive material 15, the negolyte which contains a mixture of Cu(l), and Cu(ll) is then subsequently reduced to metallic copper which depots onto electrically conductive material 15 until a thin layer of copper has been deposited. Circulation is then continued for both the posilyte and negolyte, however no voltage is applied at this point and the open circuit voltage of the cell is determined. The open circuit voltage of the cell can then be used to determine the relative state of charge of the system.

[0068] In still a further embodiment the posilyte from tank 1 is circulated through pipe 17 into pipe 20 through the use of three-way valve 3 into the half-cell containing electrically conductive material 11 through the use of pump 2. With a positive potential being applied to electrode 10 resulting in a positive voltage on electrically conductive material 11 , the posilyte which contains a mixture of Cu(l), and Cu(ll) is then subsequently oxidized to Cu(ll) and is recirculated to posilyte tank 1 through pipe 27 and pipe 22 through the use of three-way valve 8. In the same fashion the negolyte from tank 6 is circulated through pipe 19 and pipe 21 through the use of three-way valve 4 into the half-cell containing electrically conductive material 14 using pump 5. With a negative potential being applied to electrode 13 resulting in a negative potential on electrically conductive material 15, the negolyte which contains a mixture of Cu(l), and Cu(ll) is then subsequently reduced to metallic copper which deposits onto electrically conductive material 15. At this point circulation pump 5 is halted and three-way valve 3 and three-way valve 8 is closed, in essence capturing a limited amount of the posilyte inside the half-cell. Circulation for the negolyte is continued and a current is applied until all of the posilyte captured within the halfcell is oxidized entirely to Cu(ll) as indicated by a sharp and sudden rise in the cell voltage. At this point zero current is applied and the open circuit voltage is determined, then by using the Nernst equation and approximate concentration of Cu(ll) in the posilyte can be determined. In still a further embodiment the posilyte from tank 1 is circulated through pipe 17 into pipe 20 through the use of three-way valve 3 into the half-cell containing electrically conductive material 11 through the use of pump 2. With a negative potential being applied to electrode 10 resulting in a negative voltage on electrically conductive material 11 , the posilyte which contains a mixture of Cu(l), and Cu(ll) is then subsequently reduced to metallic copper and is deposited on electrically conductive material 11 recirculated to posilyte tank 1 through pipe 27 and pipe 22 through the use of three-way valve 8. In the same fashion the negolyte from tank 6 is circulated through pipe 19 and pipe 21 through the use of three-way valve 4 into the half-cell containing electrically conductive material 14 using pump 5. With a positive potential being applied to electrode 13 resulting in a positive potential on electrically conductive material 15, the negolyte which contains a mixture of Cu(l), and Cu(ll) is then subsequently oxidized to Cu(ll). At this point circulation pump 2 is halted and three-way valve 4 and three-way valve 7 is closed, in essence capturing a limited amount of the negolyte inside the half-cell. Circulation for the posilyte is continued and a current is applied until all of the negolyte captured within the halfcell is oxidized entirely to Cu(ll) as indicated by a sharp and sudden rise in the cell voltage. At this point zero current is applied and the open circuit voltage is determined, then by using the Nernst equation and approximate concentration of Cu(ll) in the posilyte can be determined.

[0069] In still a further embodiment the posilyte from tank 1 is circulated through pipe 16 into pipe 21 through the use of three-way valve 4 into the half-cell containing electrode 13. The posilyte is then further circulated through pipe 26 and pipe 24 into the negolyte tank 6 through the use of three-way valve 7. With the amount of posilyte being moved from tank 1 to tank 6 being determined to achieve the desired posilyte to negolyte volume ratio. Thereby resulting in the capability to achieve any volume ratio between the posilyte and negolyte, which typically changes over time due to osmotic effects.

[0070] In still a further embodiment the negolyte from tank 6 is circulated through pipe 18 and pipe 20 into the half-cell containing electrode 10 through the use of three-way 3. The negolyte is then recirculated through pipe 27 and pipe 22 to the posilyte tank 1 through the use of three-way valve 8. With the amount of negolyte being moved from tank 6 to tank 1 being determined to achieve the desired negolyte to posilyte volume ratio. Thereby resulting in the capability to achieve any volume ratio between the negolyte and posilyte, which typically changes over time due to osmotic effects.

[0071] It is to be understood that the terms “posilyte tank” may refer to a first tank for receiving an electrolyte, the term “electrolyte” may refer to posilyte or negolyte, usually it may refer to a posilyte in combination to posilyte tank. Similarly, the terms “negolyte tank” may refer to a second tank for receiving an electrolyte, the term “electrolyte” may refer to posilyte or negolyte, usually it may refer to a negolyte in combination to negolyte tank.

[0072] It is to be understood that the terms “first half-cell” and “second half-cell” may refer to chambers.

[0073] The terms “only the negolyte tank is in fluid connection with the second half-cell" and “only the second tank is in fluid connection with the second half-cell” as used herein and hereafter may refer to when only the negolyte tank (of the negolyte tank and the posilyte tank) is in fluid connection with the second half-cell, i.e., the posilyte tank is not in fluid connection with the second half-cell but only the negolyte tank is in fluid connection with the second half-cell. Similarly, the terms “only the posilyte tank is in fluid connection with the first half-cell" and “only the first tank is in fluid connection with the first half-cell" as used herein and hereafter may refer to when only the posilyte tank (of the negolyte tank and the posilyte tank) is in fluid connection with the first half-cell, i.e., the negolyte tank is not in fluid connection with the first half-cell but only the posilyte tank is in fluid connection with the first half-cell. Therefore, “only” used together with “the negolyte tank” (the second tank) or “the posilyte tank” (the first tank) may refer to that the specified tank of the available tanks is only in fluid connection with the specified half-cell of the available half-cells. What is the customer problem you plan to solve with your invention / idea?

[0074] With an increased level of energy insecurity in Europe regarding the volatility regarding the availability of fossil fuel energy sources increased storage capacity is needed to transition the energy sector towards renewable energy. With the aqueous all-copper redox flow battery providing the capability to store electrical energy in low consumption periods, however, technologies such as this often suffer from capacity fade over time which the current disclosure attempts to resolve through the continuous electrochemical rebalancing of the system. With what is proposed in the current disclosure we aim to produce an electrical storage technology stack that can allow the storage of large amounts of energy for timeshift, load balancing, and backup power systems for remote locations or installations and maintain high-storage level capacity for longer periods.

[0075] How does your invention / idea solve the problem?

[0076] The capacity loss in the system occurs as the active copper species distribution between the electrolytes becomes imbalanced. By employing the unique properties of copper we can continuously remove excess copper from one electrolyte as metallic copper, whilst oxidizing the copper in the second electrolyte to a copper species which can dissolve the metallic copper. By then bringing the metallic copper and the copper species from the second electrolyte into contact the copper is redissolved therefore we can effectively move the copper from one electrolyte to the other, in effect rebalancing the system and recovering any lost capacity due to imbalance. This allows us to continuously correct and mitigates capacity loss to ensure the system can always achieve an optimal capacity, preventing downtime which would result from non-continuous rebalancing techniques as proposed here.

[0077] What are the benefits to the customer?

[0078] The benefit to the customer depends on their individual needs and their use case. In the case of energy time-shift where the customer would store excess energy during high production periods and then resell the energy during high demand periods the technology as described here would allow the customer to assure that the system is always operating at or near peak storage capacity thus ensuring the maximum return on the equipment. In the case of users who might use the technology as a backup power supply for critical infrastructure such as the cellular network, they can be assured as well that the redox flow battery operates at optimal energy capacity and can easily be rebalanced to optimal capacity level continuously. That is to say without having to go down for maintenance which can offer risk if maintenance occurs when the equipment is needed to provide backup power. The technology then also allows the end user to replace older legacy systems such as backup diesel generators which have a significant environmental impact.

[0079] In all of these cases, the aqueous all-copper redox flow battery with the additional electrochemical rebalancing technology allows users to invest in long-term and long operational life energy storage. Redox flow batteries have greatly extended life cycles compared to lithium-ion backup power installation, which can not have their capacity regenerated after their capacity has dropped below minimum viable capacity for their use.

[0080] How big is the entire market? How much is it growing annually in the future? Describe your assumed first customer?

[0081] Depending on the source where you obtain the information, with Allied market research estimating the current redox flow battery market at $130 million in 2018, and expects the market to grow at a compound annual growth rate (CAGR) of 15.2 % up to $403 million in 2026. Market and Markets have a slightly higher estimate for the redox flow battery market with the market sitting at $214 million in 2021 and at a CAGR of 18%, they expect the market to reach $489 million in 2026. Redox flow batteries can replace part of the uninterruptible power supply market which is estimated to reach $14030 million in the year 2023 according to Market Watch.

[0082] The first assumed customer would be end users which control critical infrastructures such as telecommunications and power generation, with possible specific end users being Telia Oy, Fortum Oy, and Caruna Oy. Where the technology can serve as a backup power source for telecommunication and load balancing in the case of Fortum Oy and Caruna Oy. How is the problem solved currently? What are the substituting competitors (companies, products, technology)? How are you different from the competitors?

[0083] There are few viable options for large scale energy storage with the primary options being hydroelectric power storage, lithium-ion battery installations, and redox flow battery energy storage. In terms of hydroelectric power storage, the technology is limited by geographic requirements and typically has a high environmental impact and large initial investments required. Lithium-ion batteries can also serve as backup power systems but are typically not well suited to timeshift or load-balancing operations as they have limited cycles before the capacity is heavily diminished.

[0084] The more direct competitor would be vanadium redox flow batteries and ironchromium redox flow batteries, with the former having high costs associated with vanadium, equipment, materials, and difficulty in rebalancing vanadium systems to maintain high storage capacities and being temperature sensitive during operation complicating application in higher temperature locations. As for the iron-chromium redox flow batteries they have high inefficiencies due to the operating potential where energy is wasted producing hydrogen and oxygen during the charging process, and more critically chromium depending on the oxidation state has serious detrimental health effects. Additionally, for both the vanadium and ironchromium systems there is no trivial amount of work required to process the electrolytes after the plant is decommissioned, with the electrolytes posing high environmental and health risks.

[0085] The all copper redox flow battery system is different as copper is significantly lower cost compared to vanadium (x3 to x6 lower cost), and due to existing copper recycling infrastructure if the system reaches the end of life all the copper can be recovered at minimal cost and be resold or re-used in other applications. Additionally, the copper system operates at lower voltages and thus has lower efficiency losses as the system typically does not produce hydrogen or oxygen as a byproduct during the charging process. More importantly, as it relates to the current disclosure the unique chemistry of copper allows us to easily rebalance the system to restore lost capacity continuously and actively without requiring complicated rebalancing procedures or downtime of the system.

[0086] 7.1. What is the customer problem you plan to solve with your invention / idea?

[0087] With an increased level of energy insecurity in Europe regarding the volatility regarding the availability of fossil fuel energy sources increased storage capacity is needed to transition the energy sector towards renewable energy. With the aqueous all-copper redox flow battery providing the capability to store electrical energy in low consumption periods, however, technologies such as this often suffer from capacity fade over time which the current disclosure attempts to resolve through the continuous electrochemical rebalancing of the system. With what is proposed in the current disclosure we aim to produce an electrical storage technology stack that can allow the storage of large amounts of energy for timeshift, load balancing, and backup power systems for remote locations or installations and maintain high-storage level capacity for longer periods.

[0088] 7.2. How does your invention / idea solve the problem?

[0089] The capacity loss in the system occurs as the active copper species distribution between the electrolytes becomes imbalanced. By employing the unique properties of copper we can continuously remove excess copper from one electrolyte as metallic copper, whilst oxidizing the copper in the second electrolyte to a copper species which can dissolve the metallic copper. By then bringing the metallic copper and the copper species from the second electrolyte into contact the copper is redissolved therefore we can effectively move the copper from one electrolyte to the other, in effect rebalancing the system and recovering any lost capacity due to imbalance. This allows us to continuously correct and mitigates capacity loss to ensure the system can always achieve an optimal capacity, preventing downtime which would result from non-continuous rebalancing techniques as proposed here.

[0090] 7.3. What are the benefits to the customer? The benefit to the customer depends on their individual needs and their use case. In the case of energy time-shift where the customer would store excess energy during high production periods and then resell the energy during high demand periods the technology as described here would allow the customer to assure that the system is always operating at or near peak storage capacity thus ensuring the maximum return on the equipment.

[0091] In the case of users who might use the technology as a backup power supply for critical infrastructure such as the cellular network, they can be assured as well that the redox flow battery operates at optimal energy capacity and can easily be rebalanced to optimal capacity level continuously. That is to say without having to go down for maintenance which can offer risk if maintenance occurs when the equipment is needed to provide backup power. The technology then also allows the end user to replace older legacy systems such as backup diesel generators which have a significant environmental impact.

[0092] In all of these cases, the aqueous all-copper redox flow battery with the additional electrochemical rebalancing technology allows users to invest in long-term and long operational life energy storage. Redox flow batteries have greatly extended life cycles compared to lithium-ion backup power installation, which can not have their capacity regenerated after their capacity has dropped below minimum viable capacity for their use.

[0093] 7.4. How do you make money? What do you sell? Who is the customer?

[0094] There are multiple different avenues for revenue generation with this kind of technology, the simplest being licensing of the technology to already established redox flow battery manufacturers of which there are several.

[0095] The second avenue would be to manufacture the redox flow batteries and sell them to end users, where end users will tend to be renewable energy companies who want to store their excess energy during low-price periods instead sell the energy during high-price periods. Other end users would include users who have to guarantee critical infrastructure during possible power interruptions, such as telecommunications, defense contractors, and healthcare providers. A third avenue would be to manufacture the redox flow batteries for own use, with the batteries being used to store energy during energy overproduction periods and then sell the energy back to the grid at higher prices during high-demand periods.

[0096] 7.6. How is the problem solved currently? What are the substituting competitors (companies, products, technology)? How are you different from the competitors?

[0097] There are few viable options for large scale energy storage with the primary options being hydroelectric power storage, lithium-ion battery installations, and redox flow battery energy storage. In terms of hydroelectric power storage, the technology is limited by geographic requirements and typically has a high environmental impact and large initial investments required. Lithium-ion batteries can also serve as backup power systems but are typically not well suited to timeshift or load-balancing operations as they have limited cycles before the capacity is heavily diminished.

[0098] The more direct competitor would be vanadium redox flow batteries and ironchromium redox flow batteries, with the former having high costs associated with vanadium, equipment, materials, and difficulty in rebalancing vanadium systems to maintain high storage capacities and being temperature sensitive during operation complicating application in higher temperature locations. As for the iron-chromium redox flow batteries they have high inefficiencies due to the operating potential where energy is wasted producing hydrogen and oxygen during the charging process, and more critically chromium depending on the oxidation state has serious detrimental health effects. Additionally, for both the vanadium and ironchromium systems there is no trivial amount of work required to process the electrolytes after the plant is decommissioned, with the electrolytes posing high environmental and health risks.

[0099] The all copper redox flow battery system is different as copper is significantly lower cost compared to vanadium (x3 to x6 lower cost), and due to existing copper recycling infrastructure if the system reaches the end of life all the copper can be recovered at minimal cost and be resold or re-used in other applications. in

[0100] Additionally, the copper system operates at lower voltages and thus has lower efficiency losses as the system typically does not produce hydrogen or oxygen as a byproduct during the charging process. More importantly, as it relates to the current disclosure the unique chemistry of copper allows us to easily rebalance the system to restore lost capacity continuously and actively without requiring complicated rebalancing procedures or downtime of the system.

Claims

Claims1 . A device for electrochemical balancing of electrolytes of a redox flow battery, wherein the battery comprises a first half-cell and a second half-cell separated by a separator (12), wherein the device comprises: a first tank (1 ) for receiving an electrolyte; a second tank (6) for receiving an electrolyte; a plurality of connecting pipes (16, 17, 18, 19, 20, 21 , 22, 23, 24, 25, 26, 27) for passing electrolyte therethrough; a first pump (2) and a second pump (5) for pumping electrolyte, wherein the first pump (2) being configured to pump electrolyte between the first tank( 1 ), the first half-cell, the second half-cell, and / or the second tank (6), and wherein the second pump (5) being configured to pump electrolyte between the second tank (6), the second half-cell, the first half-cell, and / or the first tank (1 ); and four three-way valves (3, 4, 7, 8) configured to provide fluid connections between the first tank (1), the second tank (6), and / or the redox flow battery together with the plurality of connecting pipes and the first pump and / or the second pump.

2. The device as claimed in claim 1 , wherein the four three-way valves comprise a first three-way valve (3), a second three-way valve (4), a third three- way valve (8), and a fourth three-way valve (7), wherein the first three-way valve (3) being configured to pass electrolyte between the first tank (1) and / or the first half-cell and / or the second tank (6), the second three-way valve (4) being configured to pass electrolyte between the first tank (1 ) and / or the second half-cell and / or the second tank (6), the third three-way valve (8) being configured to pass electrolyte between the first tank (1) and / or the first half-cell and / or the second tank (6), and the fourth three-way valve (7) being configured to pass electrolyte between the first tank (1 ) and / or the second half-cell and / or the second tank (6).

3. The device as claimed in any of the preceding claims, wherein the first pump (2) being configured to pump electrolyte through the first three-way valve (3) from the first tank (1 ), at least two connecting pipes (17, 18) of the plurality ofconnecting pipes and the first half-cell, and being configured to pump electrolyte through the second three-way valve (4) from the first tank (1 ), at least two connecting pipes (16, 21 ) of the plurality of connecting pipes and the second halfcell; and the second pump (5) being configured to pump electrolyte through the second three-way valve (4) from the second tank (6), at least two connecting pipes (19, 21 ) of the plurality of connecting pipes and the second half-cell, and being configured to pump electrolyte through the first three-way valve (3) from the second tank (6), at least two connecting pipes (18, 20) of the plurality of connecting pipes and the first half-cell; wherein the first half-cell being configured to be in fluid connection through the third three- way valve (8) via connecting pipes (27, 22) of the plurality of connecting pipes into the first tank (1 ) and through the third three-way valve (8) via connecting pipes (27, 25) of the plurality of connecting pipes into the second tank (6), and wherein the second half-cell being configured to be in fluid connection through the fourth three- way valve (7) via connecting pipes (26, 24) of the plurality of connecting pipes into the second tank (6) and through the fourth three-way valve (7) via connecting pipes (26, 23) of the plurality of connecting pipes into the first tank (1 ).

4. The device as claimed in any of the preceding claims, wherein the first flow-cell comprises a first electrode (10), an electrically conductive material (11 ), and a non-conductive spacer (9); the second flow-cell comprises a second electrode (13), an electrically conductive material (15), and a non-conductive spacer (14).

5. The device as claimed in any of the preceding claims, wherein the device further comprises means for applying a voltage to the redox flow battery.

6. The device as claimed in any of the preceding claims, wherein the device further comprises means for measuring the relative electroconducting species, such as the copper species, content in the electrolytes.

7. The device as claimed in claims 6, wherein the means for measuring the relative electroconducting species is means for determing the weight of the first tank and / or the second tank.

8. The device as claimed in claims 6, wherein the means for measuring the relative electroconducting species is means for determing the volume of the electrolyte in the first tank and / or electrolyte in the second tank.

9. The device as claimed in any of the preceding claims, wherein the electrolyte comprises or consists copper species, zink species, bromine species, and / or iron species, preferably the electrolyte comprises or consists copper species.

10. The device as claimed in any of the preceding claims, wherein the redox flow battery is a copper based redox flow battery.

11. A redox flow battery system comprising: redox flow battery comprising a first half-cell for receiving an electrolyte and comprising a first electrode (10), an electrically conductive material (11 ), and a non-conductive spacer (9); and a second half-cell for receiving an electrolyte and comprising a second electrode (13), an electrically conductive material (15), and a non-conductive spacer (14), wherein the first half-cell and the second half-cell are separated by a separator (12); and the device as defined in any of claims 1 - 10.

12. The redox flow battery system as claimed in claim 11 , wherein the device and / or the redox flow battery further comprises electrolyte, such as in the first half-cell and the second half-cell and / or in the first tank and the second tank.

13. The redox flow battery system as claimed in claim 11 or 12, wherein the system further comprises an electric power source deatachable attached to the system for applying a voltage to the redox flow battery, preferably to the first electrode and the second electrode.

14. A method for determining the relative state of charge of a redox flow battery, wherein the method comprises: i) providing a redox flow battery system as defined in any of claims 11 - 13, wherein the device being configured to be in fluid connection with the redox flow battery; ii) providing electrolytes to the redox flow battery system, preferably to the first tank and the second tank of the device; iii) providing, preferably by pumping by the first and the second pump, electrolyte from the first tank through the first half-cell and electrolyte from the second tank through the second half-cell, or electrolyte from the second tank through the first half-cell and electrolyte from the first tank through the second halfcell; iv) applying a negative potential to the first electrode and a positive potential to the second electrode, or a positive potential to the first electrode and a negative potential to the second electrode, thereby resulting in the reduction of electroconducting species of the electrolyte in the half-cell comprising the electrode applied with a negative potential and thereby the electrodeposition of electroconducting species, preferably metallic copper species, on the electrically conductive material comprised in the half-cell comprising the electrode applied with a negative potential , and oxidating at least a part of electroconducting species of the electrolyte in the half-cell comprising the electrode applied with a negative potential , preferably oxidating electroconducting species of the electrolyte in the half-cell comprising the electrode applied with a negative potential to Cu(ll), on the electrically conductive material comprised in the half-cell comprising the electrode applied with a negative potential; v) stopping applying voltage to the first electrode and the second electrode; and vi) measuring the open circuit voltage of the device, thereby determining the state of charge of the electrolyte.

15. The method as claimed in claim 14, wherein, in iii), arranging the three-way valves such that only the second tank is in fluid connection with the first half-cell and providing, preferably by pumping by the second pump, electrolyte from the second tank through the first half-cell, andarranging the three-way valves such that only the first tank is in fluid connection with the second half-cell and providing, preferably by pumping by the first pump, electrolyte from the first tank through the second half-cell; and in iv), applying a negative potential to the first electrode, thereby resulting in the reduction of electroconducting species of the electrolyte in the first half-cell and thereby the electrodeposition of electroconducting species, preferably metallic copper species, on the electrically conductive material (11 ); and applying a positive potential to the second electrode, thereby oxidating at least a part of electroconducting species of the electrolyte in the second half-cell, preferably oxidating electroconducting species of the electrolyte in the second half-cell to Cu(ll), on the electrically conductive material (15), or applying a negative potential to the second electrode, thereby resulting in the reduction of electroconducting species of the electrolyte in the second half-cell and thereby the electrodeposition of electroconducting species, preferably metallic copper species, on the electrically conductive material (15); and applying a positive potential to the first electrode, thereby oxidating at least a part of electroconducting species of the electrolyte in the first half-cell, preferably oxidating electroconducting species of the electrolyte in the first half-cell to Cu(ll), on the electrically conductive material (11 ).

16. The method as claimed in claim 14, wherein, in iii), arranging the three-way valves such that only the first tank is in fluid connection with the first half-cell and providing, preferably by pumping by the first pump, electrolyte from the first tank through the first half-cell, and arranging the three-way valves such that only the second tank is in fluid connection with the second half-cell and providing, preferably by pumping by the second pump, electrolyte from the second tank through the second half-cell; and, in iv), applying a negative potential to the first electrode, thereby resulting in the reduction of electroconducting species of the electrolyte in the first half-cell and thereby the electrodeposition of electroconducting species, preferably metallic copper species, on the electrically conductive material (11 ); and applying a positive potential to the second electrode, thereby oxidating at least a part of electroconducting species of the electrolyte in the second half-cell , preferablyoxidating electroconducting species of the electrolyte in the second half-cell to Cu(ll), on the electrically conductive material (15), or applying a negative potential to the second electrode, thereby resulting in the reduction of electroconducting species of the electrolyte in the second half-cell and thereby the electrodeposition of electroconducting species, preferably metallic copper species, on the electrically conductive material (15); and applying a positive potential to the first electrode, thereby oxidating at least a part of electroconducting species of the electrolyte in the first half-cell , preferably oxidating electroconducting species of the electrolyte in the first half-cell to Cu(ll), on the electrically conductive material (11 ).

17. The method as claimed in any of claims 14 - 16, wherein, in iii), arranging the three-way valves such that electrolyte is provided from the first tank through the first half-cell and back to the first tank, and electrolyte from the second tank through the second half-cell and back to the second tank, or electrolyte from the second tank through the first half-cell and back to the second tank, and electrolytes from the first tank through the second half-cell and back to the first tank.

18. The method as claimed in any of claims 14 - 17, wherein iv) further comprises ending providing electrolyte from the first tank through the first half-cell, preferably by ending pumping by the first pump and / or arranging the three-way valves such that only the second tank is in fluid connection with the second half-cell and the first tank is not in fluid connection with the first half-cell; and providing electrolyte from the second tank through the second half-cell; and v) stopping applying voltage to the first electrode and the second electrode when essentially all of the electrolyte captured within the first half-cell is entirely oxidized, preferably the electrolyte comprising Cu(l) and Cu(ll) captured within the first halfcell is entirely oxidized to Cu(ll).

19. The method as claimed in any of claims 14 - 18, wherein iv) further comprises ending providing electrolyte from the second tank through the second half-cell, preferably by ending pumping by the second pump and / or arranging the three-way valves such that only the first tank is in fluid connectionwith the first half-cell and the second tank is not in fluid connection with the second half-cell; and providing electrolyte from the first tank through the first half-cell; and v) stopping applying voltage to the first electrode and the second electrode when essentially all of the electrolyte captured within the second half-cell is entirely oxidized, preferably the electrolyte comprising Cu(l) and Cu(ll) captured within the second half-cell is entirely oxidized to Cu(ll).

20. A method for electrochemical rebalancing of electrolytes of a redox flow battery, wherein the method comprises: i) providing a redox flow battery system as defined in any of claims 11 - 13, wherein the device being configured to be in fluid connection with the redox flow battery; ii) providing electrolytes to the redox flow battery system, preferably to the first tank and the second tank of the device; iii) providing, preferably by pumping by the first and the second pump, electrolyte from the first tank to the first half-cell and electrolyte from the second tank to the second half-cell, or electrolyte from the second tank to the first half-cell and electrolyte from the first tank to the second half-cell; iv) applying a negative potential to the first electrode and a positive potential to the second electrode, or a positive potential to the first electrode and a negative potential to the second electrode, thereby resulting in the reduction of electroconducting species of the electrolyte in the half-cell comprising the electrode applied with a negative potential and thereby the electrodeposition of electroconducting species, preferably metallic copper species, on the electrically conductive material comprised in the half-cell comprising the electrode applied with a negative potential, and oxidating at least a part of electroconducting species of the electrolyte in the half-cell comprising the electrode applied with a negative potential, preferably oxidating electroconducting species of the electrolyte in the half-cell comprising the electrode applied with a negative potential to Cu(ll), on the electrically conductive material comprised in the half-cell comprising the electrode applied with a negative potential; v) stopping applying voltage to the first electrode and the second electrode; andviii) arranging the three-way valves such that only the first tank is in fluid connection with the first half-cell and providing, preferably by pumping by the first pump, electrolyte from the first tank through the first half-cell, thereby dissoluting the electrodeposited electroconducting species, preferably metallic copper, and reducing Cu(ll) to Cu(l), or arranging the three-way valves such that only the second tank is in fluid connection with the first half-cell and providing, preferably by pumping by the second pump, electrolyte from the second tank through the first half-cell, thereby dissoluting the electrodeposited electroconducting species, preferably metallic copper, and reducing Cu(ll) to Cu(l).21 . The method as claimed in any of claims 14 - 20, wherein the method further comprises: ix) measuring the relative electroconducting species, such as the copper species, content in the electrolytes, thereby obtaining a result value.

22. The method as claimed in claim 21 , wherein, in ix), the measuring the relative electroconducting species is determing the weight of the first tank and / or the second tank, thereby obtaining one or more result values.

23. The method as claimed in claim 21 , wherein, in ix), the measuring the relative electroconducting species is determing the volume of electrolyte in the first tank and / or electrolyte in the second tank, thereby obtaining one or more result values.

24. The method as claimed in any of claims 21 - 23, wherein the metod further comprises: x) comparing the obtained result value(s) from the measuring with a predetermined value / predetermined values; xi) providing electrolytes from the first tank to the second tank if the obtained result value(s) from the measuring is / are equal or lower than the predetermined value(s), or providing electrolytes from the second tank to the first tank if the obtained result value(s) from the measuring is / are higher than the predetermined value(s).

25. The method as claimed in any of claims 21 - 24 for continuous electrochemical rebalancing of electrolytes of a redox flow battery, wherein the metod comprises the sequence of iii) to xi) two or more times.

26. A method for rebalancing of electrolytes of a redox flow battery system, wherein the method comprises: i) providing a redox flow battery system as defined in any of claims 11 - 13, wherein the device being configured to be in fluid connection with the redox flow battery; ii) providing electrolytes to the redox flow battery system, preferably to the first tank and the second tank of the device; iii) providing, preferably by pumping by the first pump, electrolyte from the first tank through the first half-cell or the second half-cell to the second tank, or providing, preferably by pumping by the second pump, electrolyte from the second tank through the second half-cell or the first-half cell to the first tank.

27. The method as claimed in claim 26, wherein, in iii), arranging the three-way valves such that the first tank is in fluid connection with the second tank only via the first first three-way valve (3), the first half-cell, the third three-way valve (8), and connecting pipes (17, 20, 27, 25), or such that the first tank is in fluid connection with the second tank only via the second three-way valve (4), the second half-cell, the fourth three-way valve (7), and connecting pipes (16, 21 , 26, 24).

28. Use of a device as claimed in any of claims 1 - 10 for determining the relative state of charge of a redox flow battery, preferably a copper based redox flow battery, for determining the relative amount of electroconducting species, such as the copper species, content in the electrolytes, for maintaining the electrolyte volumes of the electrolytes employed by redox flow battery, preferably which uses copper as the main active species, and for electrochemical balancing, preferably continuous electrochemical balancing, of electrolytes.

29. Use of a redox flow battery system device as defined in any of claims 11 - 13 for storing energy for time-shift, load balancing, and backup power systems.

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