DE102016122285A1 - Redox flow battery for storing electrical energy with radially arranged hollow fiber membranes - Google Patents

Abstract

The invention relates to a redox flow battery (RFB) for storing electrical energy. The task of finding efficient, easily scalable redox flow cells (RFC), which allows a flexible, compact structure of RFBs, is achieved according to the invention by: at least the first polarity-specific half-cell is formed of a plurality of hollow fiber membranes radially supported by inner and outer concentric retaining rings, each internally provided with a liquid-permeable electrode and connected to a first electrolyte reservoir for flowing the hollow-fiber membranes with a first electrolyte in that a chamber enclosing at least the hollow-fiber membranes of the first half-cell and having a liquid-permeable structure and an electrolytic liquid is filled with at least one conducting salt in solution, the second polarity-specific half-cell formed by a second electrolyte dur wherein the second electrolyte is in fluid communication with the first half-cell via the liquid-permeable structure and at least separated by the hollow-fiber membranes of the first half-cell.

Description

The invention relates to a redox flow battery (RFB) for storing electrical energy, comprising at least one redox flow cell (RFC) as a reaction cell with chambers as polarity-specific half-cells for catholyte and anolyte, which are separated by at least one membrane and with each an electrolyte reservoir are in communication, wherein a first and a second of the polarity-specific half-cells each with an electrolyte of at least one redox-active component, which is at least partially in substance or dissolved in a solvent and dissolved therein conductive salts, flowed through and the electrolytes in separate electrolyte circuits each with a pump device are recirculated, wherein the membrane is provided as an interface for preventing mixing or electrochemical reactions of the redox-active components with each other and for charge carrier exchange between the half-cells.

For large-scale storage of energy alkaline secondary batteries are known in the art, of which in particular tubular constructed representatives should be mentioned, because they bring the best conditions for a technologically simple enlargement of the electrochemically active surfaces.

So is in the WO 2011/161072 A1 a device is described, the alkali metal (A) and sulfur (S) in two separate, stacked tubular containers BA and BS, which are connected by means of a solid electrolyte, which passes only cations, used as active materials. The active materials may be stored as liquids in external containers and supplied to the cells as needed. The two electrode spaces of the cells are separated by a solid electrolyte (in the form of a concentric ion-conducting ceramic electrolyte tube) of alumina.

Another sodium-sulfur secondary battery is in the US 2013/0288153 A1 disclosed. Here, an ion-conducting ceramic membrane of long TiO ₂ nanotubes is provided which is capable of selectively transporting sodium ions between the anode and cathode solutions at comparatively low temperatures (<75 ° C).

Another alkaline secondary battery is in the WO 2015/035427 A1 described as a sodium-halogen battery, wherein tubular cells are separated by an ion-conducting ceramic membrane. At the negative electrode, liquid (s) of sodium (compounds) are generated by oxidation and metallic sodium is formed upon charging, and at least one reduction reaction involving a liquid halogen is carried out on the positive electrode, with the sodium ions traversing the electrolyte membrane, respectively. The two redox partners can be supplied to the cell as liquids from external storage containers. A disadvantage of these prior art alkaline secondary batteries is that in each case an ion-conducting membrane used and at elevated temperatures (often with temperatures above 290 ° C, since the most commonly used sodium must remain liquid) is operated. Lower temperatures lead to power drops because of the greatly increased internal resistance.

In the WO 2015/007382 A1 For example, micro hollow carbon nanotube or carbon nanotube compositions are described which mention, inter alia, the use in chemical energy converters and a tubular membrane electrode assembly for eliminating the known inadequate power and energy densities of redox flow batteries or fuel cells is proposed. The tubular structure has three major layers: a positive electrode and a negative electrode with a diaphragm sandwiched around an electrode therebetween. Thus, with less than 2 mm diameter of the membrane-electrode assembly higher power densities, lower manufacturing costs and lower parasitic losses can be achieved. In addition to this is the WO 2015/074764 A1 which discloses a vanadium-oxygen RFB with hollow fiber membranes in this regard. In this case, however, the negative half-cell next to the oxygen electrode located in the positive half-cell and coated with an ion-conducting membrane, two electrodes, one of solid carbon and a semi-solid electrode, wherein an electrolyte containing vanadium dissolved in acid and carbon particles dispersed therein form the semi-solid electrode wherein the carbon particle-containing electrolyte circulates within the cell with oxygen gas in a controlled humid atmosphere or in water or water vapor. In all of these secondary batteries, the efficient flow distribution and homogeneous current density distribution required for modular stackability is not optimal. In particular, in these arrangements, scaling up the size of a single RFC increases the pressure drop that occurs as the RFC flows through.

Furthermore, besides the rectangular RFB cell geometries, there is also a round arrangement DE 10 2007 034 700 A1 become known, in which a plurality of hollow profiles are clamped in parallel in a circular frame, wherein the hollow profiles represent the membrane of the RFB. In this case, the first electrolyte and the first electrode are present in the interior of a hollow profile, and the second electrolyte is externally around the hollow profile, being pumped through the cell perpendicular to the hollow profiles is placed, the second electrode at or near the hollow profile. Although the power density can be increased with this configuration, the problems of the high required pump power remain and are further increased by the different flow resistances due to the different lengths of the hollow sections. Likewise, when the circular frames are stacked one above the other, the pressure drop in the half-cell formed around the hollow profiles increases due to the increased length. Another circular approach to cell geometry is by Zheng et al. in: Journal of Power Sources 277 (2015) p. 104-109 proposed, in planar planar RFCs instead of the usual transversal-parallel flow through the electrodes radially from the outside radially to a center. Although mass transfer can thus be improved without increasing the pumping capacity, flexible assembly of RFBs by scaling of the circularly shaped electrodes and membranes quickly reaches its limits because of the increased pressure drops and the resulting increased internal electrical resistance. A homogeneous inlet and outlet of the half-cell alternately required electrolytes, catholyte and anolyte, and the sealing of the half-cells on the peripheral outer surfaces of the electrode circular disks also appears difficult to control.

The invention has for its object to find a new way to design tubular redox flow cells for storing electrical energy, which allows a simple scaling of redox flow cells and a space-saving design of redox flow batteries with high power density, energy efficiency, stability, compactness and flexibility.

According to the invention, the object of a redox flow battery for storing electrical energy, containing at least one redox flow cell as a reaction cell with chambers as polarity-specific half-cells for each electrolyte, catholyte or anolyte, which are separated by at least one membrane and each with an electrolyte reservoir in conjunction, wherein a first and a second of the polarity-specific half-cells each with an electrolyte of at least one redox-active component, which is at least partially in substance or dissolved in a solvent and dissolved therein conductive salts, flowed through and the electrolyte each with a pumping device umwälzbar are, wherein the membrane is provided as an interface for preventing mixing or electrochemical reactions of the redox-active components with each other and the charge carrier exchange between the half-cells, achieved in that at least the first polaritätsspezifisc a half-cell is formed of a plurality of hollow fiber membranes radially supported by inner and outer concentric retaining rings, each internally provided with a liquid-permeable electrode and having inner and outer retaining rings piercing ends connected to a first electrolyte reservoir such that the hollow-fiber membranes A first electrolyte flows through the first electrolyte reservoir, in that a chamber surrounding at least the hollow-fiber membranes of the first half-cell, which is formed between the concentric retaining rings, is filled with a liquid-permeable structure and an electrolytic liquid having at least one conductive salt in solution, and the second polarity-specific half-cell is flowed through by a second electrolyte and connected to the second electrolyte reservoir, wherein the second electrolyte via the liquid-permeable structure r and at least separated by the hollow fiber membranes of the first half cell interacts with the first half cell.

In a first advantageous embodiment, the chamber surrounding the hollow-fiber membranes of the first polarity-specific half cell is designed as a second polarity-specific half cell, wherein the liquid-permeable structure is electrically conductively formed as a second electrode and via a second current collector with a power connection, on the other hand via the first current collector with the first electrodes first half-cell is in electrical contact, is connected, as well as flows through the second electrolyte and is coupled to the second electrolyte reservoir.

In a second preferred embodiment, a further number of hollow-fiber membranes radially supported by two further concentric retaining rings are embedded in the hollow-permeable membranes of the first half-cell concentrically and identically structured with liquid-permeable electrodes inside the liquid-permeable structure surrounding the hollow-fiber membranes of the first half-cell formed second half-cell, wherein the liquid-permeable structure is formed by means of the Leitsalzlösung contained therein from at least one conductive salt in solution to produce an electrical connection between the first hollow fiber membranes of the first half-cell and the second hollow-fiber membranes of the second half-cell.

The hollow-fiber membranes of the first half-cell and hollow-fiber membranes of the second half-cell are each arranged alternately within a plane radially, wherein the first inner retaining ring and the first outer retaining ring of the first half-cell are pierced only by the second hollow-fiber membranes and the second inner retaining ring with a larger diameter than the first inner retaining ring and the second outer retaining ring having a smaller diameter than the first outer retaining ring are pierced by the second hollow fiber membranes within a plane alternately with the first hollow fiber membranes, and annular gaps existing inner and outer between the first and second inner retaining rings and the first and second outer retaining rings Electrolyte in / outlets for the second electrolyte of the second half cell and for flowing the first hollow fiber membranes with the first electrolyte, an inner electrolyte inlet / outlet within the first inner retaining ring and an outer electrolyte inlet / outlet outside the first outer retaining ring are provided.

In the case of hollow-fiber membranes, these membranes can be designed as ion-selective membranes and act as boundary surfaces on the principle of an ion-type exclusion. Alternatively, the hollow fiber membranes may be formed as size exclusion membranes and act as interfaces on the principle of molecular size exclusion.

Advantageously, the electrodes are formed in the interior of each hollow-fiber membrane by an electrically conductive, liquid-permeable filling material into which a wire-shaped or rod-shaped electrically conductive current collector is introduced.

The second current collector of the second half-cell is applied in an expedient embodiment on the outside of each of the hollow-fiber membranes of the first half-cell as a coating, which is contacted with an outer end to an electrically conductive framework or housing.

It proves to be advantageous if in the first and optionally second hollow fiber membranes, the electrodes are each internally applied as porous, electrically conductive coatings and the ends of the hollow fiber membranes are plugged onto current collector in the form of electrically conductive tubes or clamping sleeves.

In an expediently modified variant, the electrically conductive current collectors with an enlarged surface are at the same time designed as electrodes in the interior of the hollow-fiber membranes and - if they belong to the same half-cell - brought together to the outside.

In this case, the current collectors can preferably be rectilinearly aligned and formed with a roughened or porous surface or helically shaped or wound up.

A particularly advantageous design for an RFB results in that at least the first hollow-fiber membranes and the concentric inner and outer retaining rings provided for their radial support and the liquid-permeable structure located between the concentric retaining rings together form disc-shaped RFC modules in the form of flat cylinders of any number of variable RFC module stacks are stackable to form a freely scalable RFC. In this case, the disk-shaped redox flow cell modules are preferably stacked in a tubular module housing, wherein in the resulting RFC module stack the first and second half cells are electrically parallel coupled polarity-specific parallel and hydrodynamically also linked in parallel and form a modular RFC. In this case, the tubular module housing at least consist of an electrically insulating outer housing tube, which has an upper and a lower housing cap for closing the module housing in the upper and lower regions.

Preferably, the module housing of the RFC consists of two concentric electrically insulating housing tubes, a housing inner tube and the housing outer tube, which has the upper housing cap and the lower housing cap for closing the module housing in the upper and in the lower region. In this case, at least partially in the upper and in the lower region of at least the housing outer tube, a thread is present, in which for closing the module housing, the upper and the lower housing cap with matching threads are screwed.

The housing caps of the tubular module housing of the RFC advantageously have surface-formed, electrically conductive power connection terminals as flat connection contacts on each end face of the housing caps, wherein the power terminal of the upper housing cap is in electrical contact with the first pantograph of the first half cell and the power terminal of the lower housing cap the current collector of the second half-cell is in electrical contact and both power supply terminals are each electrically insulated from the other current collector of the other half-cell by contact insulators. the electrolyte circuits are an electrolyte inlet and an electrolyte outlet for the first at least in the housing outer tube of the tubular module housing Electrolytes of the first half-cell and a Elektrolytein- and an electrolyte outlet for the electrolyte he used second half-cell.

It proves expedient that the upper housing cap has at least one inner electrolyte inlet / outlet for the electrolyte of the first half cell and an inner electrolyte inlet / outlet for the electrolyte of the second half cell, and at least one external electrolyte inlet in the lower housing cap. / outlet for the electrolyte of the first half-cell and an outer electrolyte inlet / outlet for the electrolyte of the second half-cell is provided.

For a scaling of the performance of an RFB, the RFC is advantageously concentrically surrounded by face-mounted, flat terminal contacts of the electrically insulating tubular module housing and fixed therein, wherein at least partially each formed a thread on both an outer and on an inner side of the housing tubes is that several tubular RFCs are screwed together to form an RFC stack.

In a further advantageous embodiment, a plurality of RFCs with axes of symmetry oriented parallel to each other may be combined as single or as collinear stacked RFC in single or multi-layer arrangement in the RFB, wherein the RFC by means of contact bridges or face-side planar terminal contacts with oppositely poled, first and second power terminals connected in an electrical series circuit and are linked by connecting the first and the second half-cells with each other in each common electrolyte circuits as a hydrodynamic parallel circuit.

A preferred embodiment is that at least one tubular RFC has two electrolyte reservoirs arranged concentrically to one another and to the first and second half cells. Advantageously, several of the tubular RFCs stacked adjacent to one another in the axial direction are arranged concentrically to the two concentrically shaped electrolyte reservoirs, wherein the first and second half cells of different RFCs are hydrodynamically linked in parallel and electrically hydrodynamically to one of the concentrically arranged electrolyte reservoirs via an electrolyte circuit containing at least one pump connected in a series connection.

In an advantageous overall configuration, several of the RFBs are joined together with symmetry axes of the concentric RFCs oriented parallel to one another in a single or multilayer arrangement, connected in a hydrodynamic parallel circuit to at least partially shared electrolyte reservoirs and at least partially linked together in an electrical parallel circuit.

The invention is based on the fundamental idea that the use of a plurality of tubular membranes (hollow fiber membranes) instead of individual flat membranes, as used in all presently commercially available RFBs, the electrochemically important membrane surface per cell volume and thus the electrical performance of such a battery can increase significantly. This significantly reduces both the size and the cell weight and significantly improves the scaling potential of an RFB. The construction of known solutions for tubular RFC, however, always suffers from the fact that a single cell must be manufactured as a rigid, non-expandable structure in complicated procedures. Thus, known designs of RFC with tubular membranes do not allow flexible scaling of a single cell, but always require the scaling of a new production of all cell components, at the same time the production engineering conditions to the new requirements must be partly adapted with considerable effort. In addition, scaling in most cases involves an increased sealing effort and, above all, an increased pressure drop in at least one of the half cells when flowing through an electrolyte, which has a negative effect on the energy efficiency of an RFB. In particular, when connecting multiple RFCs to one RFBs with large electrolyte reservoirs, the great potential for efficiency, flexibility, stability, compactness, and scalability in RFC with hollow fiber membranes has not been exploited. For example, u. a. associate such space-efficient RFCs with novel modes of operation that achieve increased longevity by reducing the cross-over or cross-contamination of redox-active substances between the half-cells.

The invention therefore addresses the solution of these problems by the way of a combination of a plurality of radially disposed hollow fiber membranes and a tube construction to a disc-like module unit, the large membrane surfaces between the polarity-specific half-cells and by a reduced electrical internal resistance significantly increased power density and any and flexible scalability of a single RFC. From a multiplicity of such modular units, an RFC can then be manufactured by stacking in a tubular housing and scaled as desired by the simple stackability. At the same time, this tube construction allows a simple and reliably separated supply and removal of the two electrolytes inside and outside the hollow fiber membranes located radially therebetween with simultaneously reduced pressure loss in comparison to conventional cells in flat construction or known cells with hollow fiber membranes, without affecting the simple stackability of the modular units ,

The solution provides for a plurality of hollow fiber membranes arranged radially between at least two concentric retaining rings, which are embedded in a liquid-permeable structure are to be composed thereof by means of a plurality of hydrodynamically and electrically connected in parallel hollow fiber membranes at least one of the polarity-specific half-cells. Instead of or in addition to the coating, an electrically conductive, liquid-permeable filling material (eg, porous solid, bulk material, fiber fabric, non-woven, foam, mesh, yarn or the like) may also be introduced into the hollow-fiber membrane as an electrode. However, the liquid-permeable structure can also be formed exclusively by the cavity located between the current collector and the membrane, and the current collector can at the same time take over the function of the electrode. In this way, either only one of the polarity-specific half-cells or both half-cells can be designed.

In the first case, the first half-cell, as described above, constructed and the second half-cell by an electrically conductive, liquid-permeable structure (porous solid, bulk material, fiber fabric, non-woven, foam, mesh or the like) is formed, in which the hollow fiber (s) of the are embedded in the described radial arrangement, liquid-permeable structure or disposed therein hollow fiber membranes are each used as each equipped with an electrode electrolyte flow path for the respective half-cell. In this case, the hollow-fiber membranes of the first half-cell are radially flowed through by a first electrolyte and the liquid-permeable structure flows through between the outer and inner retaining ring in the axial or preferably likewise radial direction. In the case of radial flow, a gap between the liquid-permeable structure and the inner or outer retaining ring serves as the electrolyte inlet or electrolyte outlet.

As the current collector for the electrodes in the interior of the hollow fiber membranes, an electrically conductive wire (rod) can be introduced or the hollow fiber end of the coated with a porous electrode hollow fiber membrane grafted onto an electrically conductive tube or a clamping sleeve, wherein in each of the variants all current collector of a Half cell electrically connected in parallel.

As a current collector for the second half-cell can be at least one electrically conductive rod, strip or plate-shaped solid introduced into the liquid-permeable structure or from above or below a flat, for example, disc or annular structure pressed or placed on the liquid-permeable structure.

In the second case, if both half-cells are formed of hollow-fiber membranes with inwardly arranged rough or porous electrodes and current collectors, the hollow-fiber membranes through which different electrolytes (either catholyte or anolyte) are collected, separated according to half-cell association, are radially between at least two concentric retaining rings in a liquid-permeable one Structure arranged adjacent to another embedded, wherein the liquid-permeable structure surrounding it is filled, impregnated or flowed through with an electrically conductive salt solution, an ion-conducting solid, an ion-conducting gel or an ionic liquid. The liquid-permeable structure may, as in the first case, be in the form of a porous solid, bulk, fibrous web, non-woven, foam, mesh or the like, or be formed solely by the cavities lying between the hollow-fiber membranes of the two half-cells. The hollow-fiber membranes are preferably formed from different materials which block the redox-active components, for example plastics in the form of polymers (for example polyethersulfone) or other organic compounds and biopolymers, such as, for example, As cellulose, regenerated cellulose (RC) and other derivatives, or a ceramic.

In principle, all conceivable types of membranes can be used in the RFC according to the invention. In this context, the boundary surface between the two electrolytes or an interposed salt bridge, referred to as "membrane" according to the invention, is understood to be a planar structure which is principally characterized by the two minimum requirements, on the one hand, ensuring efficient charge equalization through the transfer of charge carriers between the half cells of an RFC On the other hand, at the same time excludes the transition of the redox-active substances of the two electrolytes in the other half cell crucial for energy storage or ideally completely suppressed electrochemical reactions of the redox-active substances of the two half-cells through the interface. According to these provisos, those membranes which act on the principle of ion-type exclusion or on the principle of size exclusion are particularly preferred. But also fabrics made of other materials, which do not bring the latter properties, are here as the half-cell limiting interface conceivable, as long as they meet the above minimum requirements. Although the term "membrane" has a limiting effect in view of the above-mentioned functions, for the sake of simplicity and since it is also the preferred variant, the sheet will be referred to as "membrane" hereinafter.

In the case of a membrane, which acts on the principle of size exclusion, the Size exclusion achieved by using redox-active macromolecules (eg, oligomers and polymers) and correspondingly selected porous membranes, whose pore size distribution is such that molecules of a certain geometric size (ie, from a certain hydrodynamic volume) or molecular mass with high probability (> 90%) within a defined period of time (eg 24 h). This is usually measured by the molecular weight of the macromolecule and an upper barrier to the pore size of the membrane, the so-called Molecular Weight Cut-Off (MWCO). As a result, macromolecular redox-active substances having a molecular weight greater than the MWCO are retained with the stated probability when using such membranes in redox flow cells, while the smaller ions of the electrolyte solution can pass through the membrane for charge equalization. For this purpose, membranes with MWCOs of at least 0.4 kDa, more preferably between 1 kDa and 10 kDa are used. But even larger MWCOs are conceivable in principle. The choice of materials according to the invention for the redox-active macromolecules and the membranes is basically arbitrary and limited only by the fact that the materials must be chemically compatible with each other and no unwanted chemical reactions with each other, so no decomposition, dissolution or otherwise dysfunctional change of the membrane material or of the electrolyte occurs.

By membranes which operate on the ion exclusion principle is meant those membranes which selectively pass ions of a given charge. This ion exclusion is achieved by electrically insulating, porous membrane materials, which are characterized in that they contain ionic groups and therefore keep electrically charged ions of the same charge from the passage, while ions of opposite charge can pass through the membrane, insofar as these ions in size at the same time do not exceed the small pore size of the membrane. A distinction is therefore made between anion- and cation-conducting membranes. A major representative of cation-conducting membranes are, for example, Nafion® membranes.

But also other types of membranes, which meet the above minimum requirements, are conceivable. Another example is ceramics, which are also commonly referred to as solid electrolyte and whose conductivity is - possibly at elevated temperature - realized by thermally mobilized ions in the solid state structure of the ceramic (eg Na ₂ O, MgO, NaAl ₁₁ O ₁₇ , etc.). Thus, in particular, all those membrane and electrolyte materials whose utility for conventional RFCs in flat construction of the prior art is already known, can profit from the additional, material-independent advantages of a tubular RFC according to the invention from module units with hollow-fiber membranes in a radial arrangement.

According to the invention, an electrolyte is understood as meaning a liquid or liquefied ion conductor which contains at least one redox-active component at least partially in substance or dissolved and optionally further additives. In principle, however, that the advantages described above of a tubular modular unit with hollow-fiber membranes are given in a radial arrangement regardless of the specific electrolytes and redox pairs used, whereby the redox chemistry actually used is in principle irrelevant to the core ideas of the invention.

With the invention, it is possible to realize a novel tubular redox flow cell of radially tubular module units (RFC modules) for storing electrical energy, with which flexibly scalable RFCs of high power density and energy efficiency can be modularly assembled with stable and reliable electrolyte recirculation flows. In addition, a simple stackability of any number of RFC modules in a housing with electrolyte connections for inlet and outlet, as well as outwardly managed electrical contacting possibilities for the polarity-specific half-cells to a compact tube as easily scalable RFC allows a variety of such RFCs - with simple Pipe connections and a common electrical interconnection - flexibly arranged to a RFB are.

The use of a salt bridge between similarly composed of hollow fiber membranes half-cells also represents a novel mode for RFBs, which in particular allows both half-cells of a tubular RFB to operate more effectively (with the same pressure gradient and higher reliability). A salt bridge according to the invention is understood to mean an ion conductor which permits an efficient exchange of ions between the half-cells and is preferably in the form of a liquid with dissolved salts, but can also be an ion-conducting solid, an ion-conducting gel or an ionic liquid. Due to the resulting double membrane (each half cell brings a hollow fiber membrane with) the undesirable, but never completely suppressible exchange of the redox-active substances between the two half-cells across the membrane away ("cross-over" or "cross-contamination") is reduced or practical almost completely suppressed. In addition, the damage of a membrane no longer leads to an involuntary mixing of the two electrolytes, as long not at least two hollow fiber membranes of different half-cells are simultaneously damaged. As a result, one or more defective hollow-fiber membranes of a half cell do not immediately lead to the failure of the functioning of the entire battery, but in the worst case, only to a reduction in performance.

• 1a: eine schematische Darstellung im Querschnitt eines ersten Ausführungsbeispiels eines erfindungsgemäßen RFC-Moduls mit einer Vielzahl von radial zwischen zwei konzentrischen Halteringen angeordneten Hohlfasermembranen einer ersten Halbzelle, die in eine elektrisch leitende flüssigkeitsdurchlässige Struktur einer zweiten Halbzelle eingebettet sind;
• 1b: eine schematische Perspektivdarstellung der Ausführung des RFC-Moduls von 1a mit Andeutung der Elektrolytströmungsverläufe beider Halbzellen;
• 1c: eine schematische Darstellung eines zweiten Ausführungsbeispiels eines erfindungsgemäßen RFC-Moduls mit zwei gleichartigen Halbzellen in Form von radial zwischen je zwei konzentrischen Halteringen fixierten Hohlfasermembranen, die abwechselnd benachbart jeweils eine Halbzelle bilden und in eine gemeinsame flüssigkeitsdurchlässige Struktur eingebettet sind;
• 2a: eine schematische Perspektivdarstellung eines Sektors des erfindungsgemäßen RFC-Moduls nach 1b in einer Ausführungsvariante mit zwei konzentrischen Halteringen, die mit elektrisch leitenden Beschichtungen versehen sind, wobei die Beschichtungen sowohl eine elektrische Parallelschaltung der inneren Stromabnehmer der ersten Halbzelle als auch von gestapelten RFC-Modulen untereinander sicherstellen;
• 2b: eine schematische Perspektivdarstellung mit zwei Axialschnitten des zweiten Ausführungsbeispiels eines erfindungsgemäßen RFC-Moduls nach 1c mit zwei zusätzlichen konzentrischen Halteringen für Hohlfasermembranen der zweiten Halbzelle, wobei ein innerer und ein äußerer Haltering elektrisch leitende Beschichtungen aufweisen, die entweder den elektrischen Kontakt zu den inneren Stromabnehmern der ersten Halbzelle bzw. der zweiten Halbzelle herstellen;
• 2c: eine schematische Perspektivdarstellung eines Ausschnitts der Hohlfasermembrandurchführung durch einen Haltering als Gestaltungsvariante zu den vorherigen 2a bis 2b mit elektrisch leitender Beschichtung, die in Kontakt zu einem als elektrische Klemmhülse ausgeführten Stromabnehmer für eine poröse Elektrode steht;
• 3a: eine schematische Perspektivdarstellung mit Axialschnitt eines ersten Ausführungsbeispiels eines rohrförmigen Modulgehäuses für eine RFC aus mehreren gestapelten RFC-Modulen, wobei das Modulgehäuse aus einem Gehäuseinnenrohr und einem Gehäuseaußenrohr mit Innengewinde und zwei darin verschraubbaren Gehäusekappen mit Außengewinde und eingearbeiteten Stromanschlussklemmen gefertigt ist;
• 3b: eine schematische Perspektivdarstellung mit Axialschnitt eines zweiten Ausführungsbeispiels eines rohrförmigen Modulgehäuses für eine RFC aus mehreren gestapelten RFC-Modulen, wobei das Modulgehäuse aus einem Gehäuseinnenrohr mit Außengewinden und einem Gehäuseaußenrohr mit Innengewinden und zwei darin verschraubbaren Gehäusekappen mit Außen- und Innengewinden und eingearbeiteten Stromanschlussklemmen gefertigt ist;
• 4a: eine schematische Perspektivdarstellung mit Axialschnitt einer ersten Ausführung eines Paares von Gehäusekappen zum Verschließen der Enden eines Modulgehäuses (ohne Stromanschlussklemmen);
• 4b: eine schematische Perspektivdarstellung mit Axialschnitt einer zweiten Ausführung eines Paares von Gehäusekappen für das Modulgehäuse mit eingearbeiteten Stromanschlussklemmen und Kontaktisolator, um jede der Halbzellen für einen RFC-Modul-Stapel nach außen kontaktierbar zu machen;
• 4c: eine schematische Perspektivdarstellung mit Axialschnitt einer dritten Ausführung eines Paares von Gehäusekappen gemäß 4b und mit konzentrischer kreisförmiger Vertiefung in der Mitte für ein Gehäuseinnenrohr gemäß 3a und 3b zur Eingrenzung des Elektrolyt-Volumens innerhalb des Modulgehäuses dient;
• 4d: eine schematische Perspektivdarstellung mit Axialschnitt einer vierten Ausführung eines Paares von Gehäusekappen für die zwei Enden des Modulgehäuses mit eingearbeiteten Stromanschlussklemmen gemäß 4b und mit konzentrischer kreisförmiger Öffnung in der Mitte, um ein Gehäuseinnenrohr gemäß 3a und 3b aufzunehmen, das der Eingrenzung des vom aus den Hohlfasermembranen strömenden Elektrolyten ausgefüllten Volumens innerhalb des Modulgehäuses dient;
• 5a:eine schematische Perspektivdarstellung mit Axialschnitt eines Ausführungsbeispiels einer Redox-Flow-Zelle, die aus neun in einem rohrförmigen Modulgehäuse gestapelten erfindungsgemäßen RFC-Modulen gefertigt ist, wobei das Modulgehäuse durch ein Paar einschraubbarer Gehäusekappen gemäß 4d hermetisch abgeschlossen wird;
• 5b: eine schematische Perspektivdarstellung eines Ausführungsbeispiels zur Realisierung einer mechanischen und elektrischen Kopplung von mindestens zwei aus jeweils mehreren erfindungsgemäßen RFC-Modulen aufgebauten RFC (beispielsweise gemäß 5a), die in je einem zusätzlichen Modulgehäuse fixiert sind, wobei durch eine Verschraubung die gegensätzlich gepolten, flächig ausgebildeten Stromanschlussklemmen beider RFCs aufeinander gepresst und die Zellen so elektrisch in Reihe geschaltet werden;
• 5c: eine schematische Darstellung einer RFB-Ausführung im Querschnitt aus einem Stapel mehrerer erfindungsgemäßer RFC-Module, wobei die flüssigkeitsdurchlässige Struktur für mehrere RFC-Module als ein Gebilde entweder axial oder radial von einem Elektrolyten durchströmt wird;
• 5d:eine schematische Perspektivdarstellung eines Ausführungsbeispiels einer RFB als Zellenstapel aus drei einfach gestapelten oder gestapelt verschraubten erfindungsgemäßen RFCs (beispielsweise gemäß 5a) mit hydrodynamisch paralleler Verknüpfung der einzelnen RFCs und elektrisch serieller Kopplung
• 5e:eine schematische Perspektivdarstellung eines Ausführungsbeispiels einer RFB aus benachbart aufgestellten RFCs gemäß 5a mit hydrodynamisch paralleler Verknüpfung der einzelnen RFCs und elektrisch serieller Kopplung flächige, gegensätzlich gepolten Stromanschlussklemmen benachbarter RFCs
• 6a: eine schematische Darstellung eines Ausführungsbeispiels einer RFB in Form einer Zellen-Elektrolytreservoir-Einheit aus zwei sich konzentrisch umgebenden Elektrolytreservoiren, die wiederum konzentrisch von einer RFC aus acht erfindungsgemäßen RFC-Modulen umgeben ist und deren Halbzellen in separaten Elektrolytkreisläufen mit je einem gemeinsamen zugehörigen Elektrolytreservoir verbunden sind;
• 6b: eine schematische Perspektivdarstellung eines Ausführungsbeispiels einer RFB in Form von zwei sich konzentrisch umgebenden Elektrolytreservoiren, die wiederum konzentrisch von wenigstens zwei gestapelten RFCs gemäß 5a, 5b bzw. 5c umgeben sind und deren unterschiedlich gepolte Halbzellen jeweils in separaten Elektrolytkreisläufen mit dem gemeinsamen zugehörigen Elektrolytreservoir verbunden sind;
• 6c: eine schematische Perspektivdarstellung eines Ausführungsbeispiels einer RFB in Form von wenigstens zwei gestapelten RFCs gemäß 5a, 5b bzw. 5c mit einer konzentrisch um ein erstes Elektrolytreservoir herum angelegten ersten Halbzelle und einem zweiten, ebenfalls konzentrischen zweiten Elektrolytreservoir,.

The invention will be explained in more detail with reference to embodiments and drawings. Showing:

• 1a a schematic representation in cross section of a first embodiment of an RFC module according to the invention with a plurality of radially arranged between two concentric retaining rings hollow fiber membranes of a first half-cell, which are embedded in an electrically conductive liquid-permeable structure of a second half-cell;
• 1b FIG. 2 is a schematic perspective view of the embodiment of the RFC module of FIG 1a with indication of the electrolyte flow courses of both half-cells;
• 1c a schematic representation of a second embodiment of an RFC module according to the invention with two similar half-cells in the form of radially fixed between two concentric retaining rings hollow fiber membranes alternately adjacent each form a half-cell and are embedded in a common liquid-permeable structure;
• 2a : A schematic perspective view of a sector of the RFC module according to the invention 1b in an embodiment with two concentric retaining rings, which are provided with electrically conductive coatings, the coatings ensure both an electrical parallel connection of the inner current collector of the first half-cell and stacked RFC modules with each other;
• 2 B : A schematic perspective view with two axial sections of the second embodiment of an RFC module according to the invention 1c with two additional concentric ferrule retaining rings for the second half-cell, wherein an inner and an outer retaining ring have electrically conductive coatings that either make electrical contact with the inner current collectors of the first half cell and the second half cell, respectively;
• 2c : A schematic perspective view of a section of the hollow fiber membrane bushing through a retaining ring as a design variant of the previous 2a to 2 B electrically conductive coating in contact with a porous electrode current collector designed as an electrical clamping sleeve;
• 3a : A schematic perspective view with axial section of a first embodiment of a tubular module housing for an RFC of a plurality of stacked RFC modules, the module housing is made of a housing inner tube and a housing outer tube with internal thread and two screwed therein housing caps with external thread and incorporated power connection terminals;
• 3b : A schematic perspective view with axial section of a second embodiment of a tubular module housing for an RFC of several stacked RFC modules, wherein the module housing is made of a housing inner tube with external threads and a housing outer tube with internal threads and two screwed therein housing caps with male and female threads and incorporated power connection terminals ;
• 4a a schematic perspective view with axial section of a first embodiment of a pair of housing caps for closing the ends of a module housing (without power terminals);
• 4b Fig. 2 is a schematic perspective view in axial section of a second embodiment of a pair of housing caps for the module housing with incorporated power terminals and contact insulator to make each of the half cells for a RFC module stack externally contactable;
• 4c FIG. 2 is a schematic perspective view in axial section of a third embodiment of a pair of housing caps according to FIG 4b and with a concentric circular recess in the middle for a housing inner tube according to 3a and 3b serves to limit the volume of electrolyte within the module housing;
• 4d FIG. 2 is a schematic perspective view, with an axial section, of a fourth embodiment of a pair of housing caps for the two ends of the module housing with built-in power connection terminals according to FIG 4b and with concentric circular opening in the middle, according to a housing inner tube according to 3a and 3b which serves to confine the volume filled by the electrolyte flowing from the hollow-fiber membranes within the module housing;
• 5a FIG. 2: shows a schematic perspective view with an axial section of an exemplary embodiment of a redox flow cell, which is manufactured from nine RFC modules stacked in a tubular module housing, wherein the module housing is formed by a pair of screw-in housing caps according to FIG 4d hermetically sealed;
• 5b : A schematic perspective view of an exemplary embodiment for realizing a mechanical and electrical coupling of at least two RFCs constructed in each case from a plurality of inventive RFC modules (for example according to FIG 5a ), which are fixed in each case an additional module housing, wherein pressed by a screw the oppositely poled, flat-shaped power supply terminals of both RFCs to each other and the cells are electrically connected in series;
• 5c a schematic representation of a RFB embodiment in cross section of a stack of several inventive RFC modules, wherein the liquid-permeable structure for a plurality of RFC modules is flowed through as an entity either axially or radially by an electrolyte;
• 5d FIG. 2: shows a schematic perspective view of an embodiment of an RFB as a cell stack of three RFCs according to the invention, simply stacked or stacked in a stack (for example according to FIG 5a ) with hydrodynamically parallel connection of the individual RFCs and electrical serial coupling
• 5e FIG. 2: shows a schematic perspective illustration of an embodiment of an RFB from adjacent RFCs according to FIG 5a with hydrodynamically parallel connection of the individual RFCs and electrical serial coupling, flat, oppositely poled current connection terminals of adjacent RFCs
• 6a : A schematic representation of an embodiment of an RFB in the form of a cell electrolyte reservoir unit of two concentrically surrounding electrolyte reservoirs, which in turn is surrounded concentrically by an RFC from eight RFC modules according to the invention and their half cells connected in separate electrolyte circuits, each with a common associated electrolyte reservoir are;
• 6b 3 is a schematic perspective view of one embodiment of an RFB in the form of two concentrically surrounding electrolyte reservoirs, which in turn are concentric with at least two stacked RFCs according to FIG 5a . 5b respectively. 5c are surrounded and their differently polarized half-cells are each connected in separate electrolyte circuits with the common associated electrolyte reservoir;
• 6c FIG. 2 is a schematic perspective view of an embodiment of an RFB in the form of at least two stacked RFCs according to FIG 5a . 5b respectively. 5c with a first half-cell concentrically arranged around a first electrolyte reservoir and a second, also concentric second electrolyte reservoir.

A Tubular Redox Flow Cell (RFC) According to the Invention 1 for storing electrical energy, as they are completely schematic only in 5c is shown contains in a basic structure at least one inventive RFC module 11 that - as in 1a shown - a variety of hollow fiber membranes 21 between at least two concentric retaining rings 3 in the radial direction preferably uniformly distributed about the axis of symmetry 35 are arranged, wherein the hollow fiber membranes 21 hermetically sealed by an inner retaining ring 31 and an outer retaining ring 32 are passed and inside the inner retaining ring 31 an inner electrolyte inlet / outlet 25 and outside the outer retaining ring 32 have an outer electrolyte inlet / outlet 26. The hollow fiber membranes 21 are inside with a first electrode 22 provided whose structure below (to 1b ) is explained in detail, and with an electrically conductive current collector 23 contacted, connecting to a power outlet 8th produces (only in 2a . 2 B and 5c shown).

The radially arranged hollow fiber membranes 21 with the electrodes 22 and the merged pantographs 23 put the first half cell 2 an RFC 1 that is from a first electrolyte 5 is flowed through and in a first electrolyte circuit 51 which is connected via a first electrolyte reservoir 52 and at least one pump 53 features (only in 5c shown). In the space between the concentric retaining rings 3 are the hollow fiber membranes 21 the first half cell 2 in a liquid-permeable structure 47 embedded, which in this example is the second electrode 42 the second half cell 4 represents and with a second electrolyte 6 is flowed through. In this case, the liquid-permeable structure 47 to the inner retaining ring 31 and to the outer retaining ring 32 each have a gap that provides an inner electrolyte inlet / outlet 45 and an outer electrolyte inlet / outlet 46, respectively. These electrolyte inlets / outlets 45 and 46 are connected to a second electrolyte circuit 61 the second half cell 4 connected, in which the second electrolyte 6 by means of at least one pump 63 via a second electrolyte reservoir 62 is circulated.

This in 1a illustrated RFC module 11 provides a base unit for a scalable RFC 1 (Redox flow cell), which is housed in a housing with multiple RFC modules 11 , at least one outer electrolyte connection for the connection of the electrolyte circuits 51 . 61 and in each case an outwardly directed electrical contacting possibility for the connection of the polarity-specific half-cells 2 . 4 with a power connection 8th , such as in 5c shown, is constructed. The entirety of one or more of such electrically and hydrodynamically interconnected RFCs 1 with at least one common electrolyte reservoir 52 . 62 at least one common associated electrolyte circuit 51 . 61 and at least one pump each 53 . 63 as well as pantographs 23 and 43 forms an RFB 7 as exemplified in 5d is specified.

The function of the RFB 7 is realized in principle in the same way as in other RFBs of the prior art, wherein in the RFC modules according to the invention 11 the use of various hollow fiber membranes 21 . 41 is possible. The hollow fiber membranes 21 . 41 can be made of different porous or non-porous materials, such as plastics in the form of polymers and their derivatives, for. Polyethylene (PE), polyurethane (PU), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVAL), polyacrylonitrile (PAN), polysulfone (PSU), polyethersulfone (PES ), Polyesters, e.g. Polyethylene terephthalate (PET), modified polyethersulfone (mPES), polyamides (PA), such as PA 6 , PA 6.6 (nylon), PA 6.10, PA 6.12, PA 11 , PA 12 , Silicone polyamides, silicone carbonate, silicone sulfone, silicone propylene; Polyimides (PI), polytetrafluoroethylene (PTFE); from polypiperazineamide in the form of thin film membranes or cellulose acetate support layer and polyamide filter cover; from organic substances such as cellulose and derivatives thereof, e.g. Regenerated cellulose (RC), cellulose ethers, cellulose esters, e.g. Cellulose nitrate, cellulose acetate (CA), cellulose triacetate (CTA), or a ceramic (e.g., Al ₂ O ₃ , ZrO ₂ , TiO ₂ , Al ₂ O ₃ + TiO ₂ , BaO + TiO ₂ , Zr ₃ (PO _{4) 4,} SiO _2, Na ₂ O, MgO, NaAl ₁₁ O _17, etc.) exist and are preferably based on the principle of size exclusion or the principle of lonentypausschlusses. The latter type of membranes consist for example of ion-conducting materials, preferably of sulfonated polymers and derivatives thereof, but also of polymers with other ionic substituents, such as. NH ₃ ⁺ , NRH ₂ ⁺ , NR ₂ H ⁺ , NR ₃ ⁺ , PR ₃ ⁺ , SR ₂ ⁺ COO ^- , PO ₃ ^2- , PO ₃ H ^- , C ₆ H ₄ O ^- , etc. (R = organic radical), wherein the polymers may correspond inter alia to those from the aforementioned list. Fluorinated polymers are particularly suitable because of their increased chemical resistance.

Examples of membranes and electrolytes according to the principle of size exclusion are a Regeneratzellulosemembran (RC) with a MWCO of 1 kDa in an electrolyte 5 . 6 from water with sodium chloride as conductive salt and one each in the electrolyte 5 . 6 for the respective half cell 2 . 4 dissolved polymer (molecular weights greater than 1 kDa) as redox-active substance; a Regeneratzellulosemembran with a MWCO of 5 kDa in an electrolyte 5 . 6 from propylene carbonate and with tetrabutylammonium hexafluorophosphate as the conductive salt and one each in the electrolyte 5 respectively. 6 for the respective half cell 2 . 4 dissolved polymer (molecular weight greater than 5 kDa) as redox-active substance; a polyethersulfone membrane with a MWCO of 3 kDa in water with potassium chloride as the conductive salt, each with one in the electrolyte 5 respectively. 6 for the respective half cell 2 . 4 dissolved polymer (molecular weight greater than 3 kDa) as redox-active substance, etc. Here are the Hohfasermembranen 21 . 41 as size exclusion membranes each selected so that the MWCO of the hollow fiber membrane 21 . 41 is below the value for the number average molecular weight of the redox-active macromolecule used.

An example of a tubular RFC based on the ion-type exclusion principle 1 would be a variety of hollow fiber membranes 21 . 41 from Nafion® in an electrolyte 5 . 6 from sulfuric acid with vanadium pentoxide as redox-active substance, this being an important material construction known from commercial flat-membrane RFBs. For the electrolytes 5 . 6 In addition, as already indicated above, at least all those electrolyte materials that can be used by conventional RFB 7 are known in the art. This includes in particular important representatives, such as an electrolyte 5 . 6 from aqueous sulfuric acid with dissolved vanadium pentoxide, an electrolyte 5 . 6 from aqueous sodium chloride solution with dissolved TEMPO or Viologen polymer, an electrolyte 5 . 6 from aqueous zinc and ammonium chloride solution with dissolved TEMPO polymer (or non-polymeric TEMPO derivatives) or an aqueous zinc bromide solution. However, other redox couples are possible which are dissolved in organic solvents such as acetonitrile, propylene carbonate, ethylene carbonate / dimethyl carbonate, dimethyl sulfoxide, toluene, dimethylformamide, and others. Likewise acids, bases and ionic liquids make suitable solvents for the electrolytes 5 . 6 represents.

For this reason, the electrolyte and membrane materials listed above are only examples chosen more or less arbitrarily, their functionality already being described in the literature (see, for example, US Pat. J. Noack et al., In: Angew. Chem. Int. Ed. 2015, 54, 9776-9809, or J. Winsberg et al., In: Angew. Chem. Int. Ed. 2016, DOI: 10.1002 / anie.201604925R1 ) has been sufficiently demonstrated for RFCs with flat membranes and thus of course also for use in an RFB according to the invention 7 are suitable with their aforementioned advantages.

1b shows in a perspective view the configuration of an RFC module 11 according to 1a , wherein the first half cell 2 from a plurality of radially arranged hollow fiber membranes 21 inside with an electrolyte-permeable electrode 22 and a pantograph inserted therein 23 are provided, and the second half cell 4 with a continuous graphite felt as a liquid-permeable structure 47 as a porous second electrode 42 Is provided. It is for the first half cell 2 to mention that the liquid-permeable electrodes 22 can be made porous or otherwise liquid-permeable with a wide variety of materials, processes and constructions. An embodiment of the electrodes 22 represent porous electroconductive coatings on the inside of the hollow fiber membranes 21 can be applied by suitable methods, such as vapor deposition, thermal spraying, dip coating and printing methods. The material of the hollow fiber membrane 21 itself ensures the electrical insulation of the respective porous first electrode 22 the hollow fiber membrane 21 from the liquid-permeable structure 47 the second electrode 42 outside the hollow fiber membrane 21 , In addition, in further embodiments of the electrodes 22 instead of or in addition to the membrane coating, the interior of the hollow-fiber membranes 21 be completely filled with liquid-permeable, electrically conductive materials, for example in the form of bulk materials (such as irregular or regularly shaped small parts, beads, very small grains, etc.) of electrically conductive or conductive coated plastic, carbon, aluminum, copper, zinc, nickel, Silver or other metals, alloys or conductive materials, felts, woven fabrics, knitted fabrics, knitted fabrics, nonwovens, papers, meshes or lattice-like structures, foams, fibers and / or yarns of conductive or conductive coated materials (as in the above-mentioned bulk solids) , A further embodiment is that - especially in hollow-fiber membranes with a small diameter (<500 microns, but not limited to this size) - the fact that the inside of the individual hollow-fiber membrane 21 inserted or otherwise as centrally as possible introduced cylindrical or rod-shaped pantograph 23 from the electrolyte 5 can be flowed around without being surrounded by a separate flow-inhibiting material. In this case, the surface of the pantograph 23 be artificially enlarged by increased surface roughness, meandering, helical or rib structure or shaping as a tube.

For the second half cell 4 is essential that the liquid-permeable structure 47 the second electrode 42 from the same materials as above for the first electrodes 22 described, may exist and also a coating on the outer surfaces of the hollow fiber membranes 21 the first half cell 2 may be provided, wherein the retaining rings 3 but in each case a gap (annular gap) between the inner retaining ring 31 and the outer retaining ring 32 remains as the inner electrolyte inlet or outlet 45 and as outer electrolyte inlet or outlet 46 for the supply or discharge of the in a second electrolyte circuit 61 (only in 5c drawn) circulated second electrolyte 6 is provided. The flow direction is arbitrary and takes place in the radial or axial direction through the electrode 42 therethrough. In the same way, the first electrolyte 5 through the radial in the retaining rings 3 arranged hollow fiber membranes 21 flow either radially inward or radially outward. The integration into the electrolyte circuit 51 (in 1a - 1c not shown) can by means of an outer module housing 13 (only in 1c drawn) limited external space around the outer retaining ring 32 and one within the inner retaining ring 31 existing interior, its volume with an additional concentric housing inner tube 131 (in 1b not drawn, see z. B. 5a . 5d . 5e ) may be limited.

In a slightly modified (not shown) variant of this embodiment of an RFC module 11 according to 1b is in the same arrangement of retaining rings 31 . 32 provided that the hollow fiber membranes 21 instead of an arrangement within a single layer in at least two vertical (ie along the axis of symmetry 35 offset) adjacent layers are arranged, which may result in retaining rings 31 and 32 with mutually different diameters, for example, to a denser hollow fiber packing, as compared to the stacking RFC modules 11 according to 1a or 1b it is possible. In general, however, the design is a single-layer RFC module 11 prefers.

1c shows another embodiment of the tubular RFC module 11 in which the first half cell 2 and the second half cell 4 in the same way from hollow fiber membranes 21 and 41 be formed and alternately between the retaining rings 3 are arranged. For the separated supply of the first and the second electrolyte 5 and 6 are in this example a first and a second inner retaining ring 31 and 33 and a first and a second outer retaining ring 32 and 34 available. In the execution of 1c each end the hollow fiber membranes 41 the second half cell 4 in the resulting intermediate spaces (annular gaps) between the inner retaining rings 31 and 33 or between the outer retaining rings 32 and 34, while the ends of the hollow fiber membranes 21 the first half cell 2 inside the first inner retaining ring 31 and end outside the first outer retaining ring 32. The space outside the first outer retaining ring 32 is doing by a concentrically arranged module housing 13 limited to the outside. As a result, the separate supply and removal of the two electrolytes 5 and 6 ensured by the annular gaps. In the space between the second inner retaining ring 33 and the second outer retaining ring 34 is located, as in the previous one 1a and 1b , a liquid-permeable structure 47 into which the two groups of hollow-fiber membranes 21 and 41 are embedded. This liquid-permeable structure 47 is with a conductive salt solution 84 impregnated, which is the electrical contact between the hollow fiber membranes 21 the first half cell 2 and the hollow fiber membranes 41 the second half cell 4 taught. It thus provides a Leitsalzbrücke between the two half-cells 2 and 4 and thus closes the circuit between those with the power connector 8th (not shown here) connected half-cells 2 and 4 , This conductive salt solution 84 consists of the same solvents and conductive salts that make up the electrolytes 5 . 6 this RFB 7 consist. This stands for the conductive salt solution 84 the same range of materials available, including for the electrolytes 5 . 6 already mentioned above by way of example.

A slightly modified (not shown) variant of this version of an RFC module 11 according to 1c sees the same arrangement of retaining rings 31 . 32 . 33 . 34 before, at which the hollow fiber membranes 21 and 41 however, instead of being located in at least two vertical (ie along the axis of symmetry 35 extending) adjacent layers and the hollow fiber membranes 21 and 41 every half cell 2 and 4 within one shift, however, per half cell 2 and 4 formed in adjacent layers.

In general, a single-layer RFC module 11 , as in the embodiments according to 1a . 1b and 1c shown, however, the preferred variant, since a simple stacking of such RFC modules 11 automatically leads to a multilayer arrangement. However, multi-layered hollow fiber assemblies within a group of holding rings can result in reducing the spaces between the hollow fiber membranes used in RFC modules 11 with small diameter of the innermost retaining ring 31 and large diameter of the outermost retaining ring 32 can be beneficial.

Furthermore, the said radial arrangement of the hollow fiber membranes 21 (or 41) for any execution of an RFC module 11 not necessarily on a straight course of the hollow fiber membranes 21 (or 41) to the common center out. Also, the use of slightly curved or curved hollow fiber membranes 21 (or 41) is conceivable and advantageous, for example, if the membrane surface or the electrolyte content in the interior of the hollow-fiber membranes 21 (or 41) is to be further increased, without the diameter of the RFC module 11 to enlarge.

2a shows a possibility for advantageous summary of the current collector 23 of the first half-cell 2 an RFC module according to the invention 11 to 1b in a schematic perspective view with two axial sections of an embodiment of the RFC module 11 , These are on the two concentric retaining rings 3 , which consist of an electrically non-conductive material, on the inner retaining ring 31 inside and on the outer retaining ring 32 each externally either electrically conductive coatings 38, for example made of carbon, a carbon composite, a metal (eg., Aluminum, copper, zinc, nickel, silver, etc.) or an alloy (eg., Stainless steel), applied or laid or the retaining rings 31 . 32 at least partially coated with such material (eg vapor deposited or deposited). The electrically conductive coatings 38 the retaining rings 31 and 32 are in electrical contact with the pantographs 23 the first half cell 2 and thus act as a common concentric contact of the otherwise of the plurality of hollow fiber membranes 21 radially outgoing rod or wire-shaped pantograph 23 ,

When stacking multiple RFC modules 11 get the retaining rings 31 . 32 in mechanical contact with adjacent RFC modules 11 , whereby the coatings 38 the retaining rings 31 . 32 of different RFC modules 11 in electrically conductive contact with each other and get an electrical parallel connection of the first half-cells 2 all stacked RFC modules 11 in the RFC 1 results. Also the second half cells 4 all RFC modules 11 are stacked together electrically in the stacking, as per RFC module 11 disk-shaped second electrodes 42 the second half cells 4 various RFC modules 11 solely electrically connected by their stacking. For current collection in this embodiment, electrically conductive rods (eg of carbon, a carbon composite, aluminum, copper, zinc, nickel, silver, stainless steel, etc.) as the second current collector 43 into the second electrode 42 the second half cell 4 inserted.

The previously described solution of electrically non-conductive retaining rings 31 . 32 and an electrically conductive coating 38 can material side also be readily realized in the reverse manner by electrically conductive retaining rings 31 . 32 and an electrically non-conductive coating (eg, a plastic or paint) is used. The contact remains the same in this case and results between the RFC modules 11 continue by simple stacking.

2 B shows a similar 2a sector of an RFC module generated by two axial sections 11 for the embodiment of the RFC module 11 according to the invention, in which both half-cells 2 and 4 with hollow fiber membranes 21 and 41 are realized and the liquid-permeable structure 47 between the second inner retaining ring 33 and the second outer retaining ring 34 only the electrical coupling between the hollow fiber membranes 21 and 41 by means of a conductive salt solution contained therein 84 manufactures. The pantographs 43 are analogous to 2a each to electrically conductive coatings 39 on the second inner and outer retaining rings 33 . 34 electrically contacted. Here are the second retaining rings 33 . 34 - unlike in the execution according to 1c - not both within the first retaining rings 31 and 32 arranged, but first and second inner retaining rings 31 . 33 and first and second outer retaining rings 32 . 34 are radially offset in the same way.

In addition, in 2c as a detail supplement for electrical contacting of the electrodes 22 . 42 in an RFC module 11 according to 1a to 1c a perspective schematic representation shown in the hollow fiber membranes 21 . 41 an electrically conductive, porous coating as a porous electrode 22 . 42 have and the pantographs 23 . 43 are formed as electrically conductive clamping sleeves, which when plugging on the retaining ring 31 . 32 and the hollow fiber membrane 21 . 41 simultaneously in electrical contact with the electrically conductive coating 38 . 39 of the retaining ring 31 , 32 and the electrode formed as a coating 22 . 42 devices.

3a and 3b show in a perspective view with axial section depending on an embodiment of a module housing 13 , which consists of two concentrically surrounding tubes, a housing inner tube 131 and a housing outer tube 132, wherein at least the housing outer tube 132 in the upper and lower part of a thread 135 having ( 3a ). But also the housing inner tube 131 Can be threaded at the top and bottom 135 exhibit ( 3b ). Both threads 135 serve the purpose of an upper housing cap 133 and a lower housing cap 134 , in turn, with a matching thread 135 and an inner opening 136 are provided in the middle, with the housing inner tube 131 and the housing outer tube 132 to screw and so form a closed module housing 13. Ring seals, not shown, can additionally be placed on the upper and lower edges of the housing inner and outer tubes 131 and 132, which when the housing caps are screwed on 133 . 134 each provide an additional hermetic seal.

4a to 4d show four further embodiments of the housing caps 133 and 134 in perspective views with axial sections. In a first embodiment are the upper and lower housing cap 133 . 134 circular, as in 4a drawn, with a thread 135 provided and otherwise configured as a full form without further cutouts or openings. Such housing caps 133 . 134 consist entirely of an electrically non-conductive material. 4b shows a similar structure as 4a , however, is characterized in that in the housing caps 133 . 134 one power connector each 24 respectively. 44 is incorporated to the half cells 2 and 4 to contact the outside electrically. This is the upper case cap 133 (left in 4b ) made of an electrically conductive material and thus as a surface connection contact 81 the first power connector 24 provided and one in the housing cap 133 introduced concentrically about the axis of symmetry 35 trained ring as a contact insulator 82 between the live parts of the two half-cells 2 . 4 intended. The lower housing cap 134 (right in 4b ) is basically made of a non-conductive material as a contact insulator 82 manufactured and concentric about the axis of symmetry 35 formed ring of electrically conductive material is as a power terminal 44 intended.

A third embodiment according to 4c differs from the previous embodiment according to 4b only in that a circular cutout in each case in the middle of the housing caps 133 . 134 as an inner opening 136 is introduced, in which a housing inner tube 131 can be inserted or screwed, wherein the respective housing cap 133 . 134 but still limited by a closed area.

4d illustrates a fourth embodiment, which is similar to the embodiment according to 4c still with an inner opening 136 is provided as a circular cut in the middle, however, in contrast to the previous version, this milled cut completely through the housing cap 133 . 134 passes through and this is now not limited by a closed, but by an annular surface, to the outside.

The non-conductive parts of the module housing 13 and in particular the housing caps 133, 134 are z. B. from a polymer, the against the electrolyte used 5 . 6 chemically resistant, such as polyethylene (PE), polypropylene (PP) or polytetrafluoroethylene (PTFE). The electrically conductive housing parts are preferably made, for example, of carbon, a carbon composite, a metal (eg, aluminum, copper, zinc, nickel, silver, etc.) or an alloy (eg, stainless steel) or at least with such a material coated. The choice of material is based on the specification of the electrical conductivity as well as chemical and electrochemical resistance, ie in particular that no undesired side reactions between the electrolyte or the electrodes and the module housing materials may occur. Such unwanted side reactions include, in particular, complete or partial dissolution of the housing material in the electrolyte, corrosion or other electrochemical reactions between the electrolyte, electrode and housing that do not correspond to the electrochemical reaction of the redox-active substances intended for energy storage.

In 5a is an embodiment of an RFC 1 shown in perspective view with axial section, which consists of nine identical RFC modules according to the invention 11 in the execution according to 1a that exists in a module housing 13 are simply stacked. The module housing 13 is in this embodiment by two housing caps 133 . 134 according to the execution 4d closed, which thus simultaneously the external electrical contacts of the RFC 1 form. The number of hollow fiber membranes in each RFC module 11 is chosen so that the volume of the first and the second half cell 2 . 4 is the same size. Both half cells 2 . 4 are flowed through radially.

By stacking the RFC modules 11 have the pantographs 23 the first half cells 2 or the liquid-permeable structures 47 the second half cells 4 adjacent stacked RFC modules 11 each electrically conductive contact each other. The upper housing cap 133 When screwing with their electrically conductive parts on the current collector 23 the first half cell 2 pressed and brought into electrically conductive contact with these, causing the housing cap 133 as power connection terminal 24 can be used. The lower housing cap 134 when screwed into the module housing 13 in an analogous manner with their electrically conductive parts on the porous second electrode 42 of the lowest RFC module 11 pressed and thus acts at the same time as a pantograph 43 for the second half cell 4 and to the outside as a power terminal 44 ,

5b shows one way, like two RFCs 1 which according to 5a are configured to be coupled mechanically and electrically in a simple manner. For this every RFC 1 in a tubular stack housing 71 introduced, which in the upper area outside a thread 135 and in the lower area inside a matching thread 135 whereby at least two such RFCs made in this way are obtained 1 can be screwed together by a simple screw. They get caught by the power connection terminals 24 and 44 trained opposite poles of neighboring RFCs 1 in electrically conductive contact and are thus electrically connected in series. In addition, RFCs 1 , which are screwed stacked in this way, with a hydrodynamic parallel circuit of similar half-cells 2 . 4 various RFCs 1 operated in a stack (only in 5d drawn).

5c schematically represents a redox flow battery 7 as a cross-section in its entirety from an RFC 1 with five RFC modules 11 , associated electrolyte reservoirs 52 . 62 and electrolyte circuits 51 . 61 with pumps 53 . 63 It is irrelevant whether the flow direction in the porous electrode 42 the second half cells 4 in the radial direction, as in 1b between an inner electrolyte inlet or outlet 45 and an outer electrolyte inlet or outlet 46, or vertically through all five RFC modules 11 is pumped, but omitted in vertical flow, the electrolyte inlets or outlets 45, 46. The radial flow is used because of the lower pressure drop as a preferred variant.

An embodiment of a redox flow battery 7 consisting of several simple stacked RFCs 1 exists is in 5d shown in a perspective view with axial section. In this embodiment, the RFB exists 7 from three RFCs 1 of which two, each with three stacked RFC modules according to the invention 11 are equipped and one with five RFC modules 11 Is provided. The module housing 13 all RFCs shown here 1 in this example correspond to the embodiment according to 5a , Instead of simply stacking the RFCs 1 These can also in the embodiment according to 5b be bolted together. In both cases, two opposing poles are adjacent to stacked RFCs 1 through the housing caps 133 . 134 as power connection terminals 24 and 44 in electrically conductive contact. The number of stacked RFC modules 11 and the interconnected RFCs 1 within an RFB 7 results from the electric power to be generated, which for a particular application of the RFB 7 and the voltage of the individual RFCs that can be achieved by the selected redox-active substances 1 ,

Also shows 5d a possibility of hydrodynamic parallel connection with simultaneous electrical serial coupling of several RFCs 1 , Here are all the first half cells 2 the three RFCs 1 in hydrodynamically parallel connection with an electrolyte reservoir 52 through a common electrolyte circuit 51 connected, in which by at least one pump 53 the electrolyte 5 through the RFCs 1 is pumped. Analogously, all second half cells 4 the three RFCs 1 in hydrodynamically parallel connection with an electrolyte reservoir 62 through a common electrolyte circuit 61 connected, in which by at least one pump 63 the electrolyte 6 through the RFCs 1 is pumped. The upper housing cap 133 with a power terminal 24 the top RFC 1 in the RFC stack and the lower case cap 134 with a power terminal 44 the lowest RFC 1 form the two poles of the RFB in such a cell stack 7 ,

In addition, another embodiment of an RFB 7 from such RFCs 1 with flat connection contacts 81 for the power connection terminals 24 . 44 in a spatial representation in 5e with six RFCs 1 shown. Here are the RFCs 1 with alternately switched polarity in two rows of three RFCs each 1 juxtaposed and again in each case the two half-cells 2 . 4 all RFCs 1 in each case an electrolyte circuit 51 . 61 hydrodynamically connected in parallel with each other. The electrical series connection of the RFCs 1 is in this case over flat contact bridges 83 reached, each two adjacent RFCs 1 connect electrically conductively in serial coupling at their opposite poles. The contact bridges 83 For example, they may consist of carbon, a carbon composite or preferably a metal, such as copper or aluminum, or an alloy (eg stainless steel) or the like.

In 6a is an embodiment of an RFB according to the invention 7 shown as a cell electrolyte reservoir unit, which can not be meaningfully realized for conventional flat-type RFCs, but in an RFC according to the invention 1 due to the tube shape a particularly compact design of a RFB 7 represents. For this, at least one RFC according to the invention 1 (drawn here as an axial section) concentrically around two likewise concentrically surrounding electrolyte reservoirs 52 and 62 arranged, from which the two half-cells 2 and 4 over pumps 53 and 63 be fed.

It is also possible to form such a cell electrolyte reservoir unit from a plurality of RFCs 1, wherein the RFCs 1 in a first variant according to 5a with flat connection contacts 81 the power connection terminals 24 and 44 equipped and - similar to in 5d shown - axially simply stacked and at the same time concentrically around the electrolyte reservoirs 52 and 62 are arranged as it is in 6b is shown in a perspective view with axial section. It is instead of a simple RFC module stack 12 also a bolted stack when executing the RFCs 1 according to 5b possible.

In a second variant, the in 6c is shown as a perspective schematic representation, are one or more axially stacked RFCs 1 concentric around an electrolyte reservoir 62 for the electrolyte 6 arranged while a second electrolyte reservoir 52 for the electrolyte 5 again concentrically around the RFC (s) 1 and the electrolyte reservoir 62 is formed around. The so connected RFCs 1 In turn, all variants are operated hydrodynamically in parallel.

It is also conceivable, according to several such cell electrolyte reservoir units 6a to 6c next to each other stacked in a layer or in several layers stacked and arranged one behind the other, analogous to the embodiment of simple RFBs 7 as exemplified in 5e are shown. Such assemblies of multiple cell electrolyte reservoir units can then be used as a large battery.

For all illustrated embodiments of an RFC 1 or RFB 7 can use RFC modules in the same way 11 in the execution according to 1c instead of the execution according to 1a and 1b be used. The only difference is that the half cells 2 and 4 as described above, in the same way through the interior of the identically constructed hollow fiber membranes 21 and 41 are formed and the liquid-permeable structure 47 with a conductive salt solution 84 is designed as a salt bridge.

The following explanations are intended to illustrate exemplary possibilities for the realization of electrodes 22 . 42 and pantographs 23 . 43 for the hollow fiber membranes 21 . 41 and can in principle be used for all the preceding embodiments, ie can be combined with them or implemented in them.

It becomes an RFC 1 from RFC modules according to the invention 11 produced. A first embodiment of the electrodes 22 respectively. 42 for an RFC module 11 of this type are porous coatings. On the inside and the outside of the hollow fiber membranes 21 . 41 For this purpose, by suitable methods, such as, for example, vapor deposition, thermal spraying, dip coating and printing methods, in each case an electrically conductive porous coating is applied which acts as a porous electrode 22 or at least as part of the electrode 22 serves. The choice of coating process is in principle limited by the fact that the hollow fiber membranes 21 . 41 or their possible support structures are not dissolved or otherwise destroyed or a pore structure of the hollow fiber membranes 21 . 41 Not completely clogged or damaged. The material of the hollow fiber membrane 21 itself ensures the electrical insulation of the respective porous first electrode 22 on the inside of the hollow fiber membrane 21 and the porous second electrode 42 on the outside of the hollow fiber membrane 41 from each other to exclude short circuits. The thus created small distance between the electrodes 22 and 42 , which ranges from 10 μm to a few hundred microns, ensures minimal diffusion paths of the ions of the saline solution 84 , resulting in a reduction of the internal resistance of the RFC 1 leads compared to conventional RFCs with flat membranes. For RFCs according to the invention 1 , which are configured in a variant with salt bridge, the described embodiment of the electrodes 22 also only on the inside and both for the hollow fiber membranes 21 a first half cell 2 as well as the hollow fiber membranes 41 and the associated electrodes 42 a second half cell 4 happen.

In addition, in a second embodiment of the electrodes 22 . 42 instead of or in addition to a membrane coating, the interior space and the exterior space of the hollow-fiber membranes 21 . 41 completely with liquid-permeable, electrically conductive materials as electrodes 22 . 42 fill out. These liquid-permeable materials may, for example, be in the form of bulk solids (eg of irregularly or regularly shaped small parts, such as globules, very small grains, etc.) of electrically conductive or conductively coated plastic, carbon, aluminum, copper, zinc, nickel, silver, or other metals, alloys (eg stainless steel) or conductive materials, as long as they are electrochemically stable in the respective electrolyte and do not undergo unwanted side reactions, felts, woven fabrics, knitted fabrics, knitted fabrics, nonwovens, papers, meshes or lattice-like structures, foams, Fibers and / or yarns of conductive or conductive coated plastic, carbon, carbon composites, metals (eg aluminum, copper, zinc, nickel, silver, etc.) and / or alloys (eg stainless steel) are present.

Also in an RFC 1 for which a first half cell 2 through the hollow fiber membranes 21 and a second half-cell 4 through the hollow fiber membranes 21 surrounding chamber is formed, which may be the hollow fiber membranes 21 surrounding spaces with an electrically conductive, liquid-permeable structure 47 as a porous second electrode 42 in the form of bulk solids (eg of irregularly or regularly shaped small parts, such as beads, very small grains, etc.) of electrically conductive or conductively coated plastic, carbon, aluminum, copper, zinc, nickel, silver, or other metals, alloys ( eg stainless steel) or conductive materials, as long as they are in the respective electrolyte 5 . 6 are electrochemically stable and do not undergo unwanted side reactions), felts, fabrics, knits, knits, nonwovens, papers, meshes or lattice-like structures, foams, fibers and / or yarns of carbon, carbon composites, metals (eg aluminum, copper, zinc , Nickel, silver, etc.) and / or alloys (eg stainless steel). Also alternately stacking thin porous electrode layers of the aforementioned or similar materials and layers of hollow fiber membranes 21 is conceivable.

Inside the hollow fiber membranes 21 such RFC 1 can the porous electrode 22 are then also realized by liquid-permeable, electrically conductive structures, for which also the embodiments and materials previously described for the exterior space come into question. In particular, however, electrically conductive wires or rods with and without brush-like or otherwise porous coating, porous rods or strand-like structures (eg fibers, yarns, fabrics, etc.) of the abovementioned materials can also be used as electrodes in the interior 22 be used. Furthermore, simple or additionally chemically or mechanically roughened wires, rods or other non-porous string-like structures can be used for this purpose.

Further, the porous electrodes 22 . 42 instead of them on the hollow fiber membrane as described above 21 . 41 to precipitate or in any way in the finished hollow fiber membrane 21 . 41 also be realized by processes in which the membrane material on corresponding preformed liquid-permeable electrically conductive structures, as described above, is deposited.

As a pantograph 23 . 43 for the hollow fiber interior of the hollow fiber membranes 21 . 41 located electrodes 22 . 42 are electrically conductive wires or rods (eg., From electrically conductive or conductive coated plastic, carbon, carbon composite, aluminum, copper, zinc, nickel, silver, stainless steel, etc.), which are preferably roughened or porous and in the case of porous electrodes 22 . 42 can be simply inserted into the porous electrode material or woven directly in wick-like structures. For electrodes 22 and 42 , which are formed as a membrane coating, the current decrease by at least one each in the interior of the hollow fiber membranes 21 . 41 to the porous coating material of the electrodes 22, 42 applied electrically conductive wire, rod, strip or similar strand-like shaped pantograph 23 which leads axially outward, or by slipping the (also coated) ends of the hollow fiber membranes 21 . 41 on electrically conductive tubes (not shown) take place. The latter can then be electrically connected in parallel to each other by wire or a second, electrically conductive framework. On additional pantographs 23 . 43 can be completely dispensed with in a further variant, if the material of the electrodes described above 22 . 42 also at the same time as a pantograph 23 . 43 led to the outside and can be summarized.

The dimensions of the individual RFC modules 11 , ie their diameter-to-thickness combinations, are largely arbitrary and depend on the desired performance of the RFC 1 or the RFB 7 from. An optimal diameter-thickness ratio is primarily due to stability criteria and the hydrodynamics in cell operation and the electrical resistance of the current-carrying parts in the RFC module 11 affected. The reasonable maximum width of the half cells 2 . 4 , which are the diameters of the respective outer retaining ring 32 or 34 and the respective inner retaining ring 31 or 33 all retaining rings 3 in the RFC module 11 results depends inter alia on the pressure loss of the electrolytes 5, 6 when flowing through the individual RFC modules 11 within the circuits operated by the pumps 53, 63 51 . 61 and half cells 2 . 4 while the maximum length of an RFC according to the invention 1 from several stacked RFC modules 11 Above all, it is determined by the electrical internal resistance, which occurs when discharging the charges released in the electrochemical reactions via the electrodes 22 . 42 to the pantographs 23 . 43 and finally to the external electrical contacts of the RFC 1 in the form of power connection terminals 24 . 44 results. Powerful RFCs 1 will barely exceed a maximum length of 10 m, preferably 0.1 m to 1 m long, and have an outer diameter of at most 10 m, preferably 0.05 m to 1 m. It is also the thickness of the half-cells 2 . 4 (radial extent), which is not greater than 1 m for each half cell 2 . 4 , preferably in the range of 0.5 cm to 25 cm.

LIST OF REFERENCE NUMBERS

1

Redox Flow Cell (RFC)

11

Redox Flow Cell Module (RFC Module)

12

RFC-modulus staple

13

module housing

131

Housing inner tube

132

Housing outer tube

133

upper housing cap

134

lower housing cap

135

Thread (from the housing inner / outer tube or housing cap)

136

inner opening (the housing cap)

2

first half cell

21

(first) hollow fiber membrane

22

(porous) (first) electrode

23

(first) pantograph

24

(first) power connection terminal

25

internal electrolyte inlet / outlet (for first electrolyte)

26

outer electrolyte inlet / outlet (for first electrolyte)

3

(concentric) retaining rings

31

(first) inner retaining ring (for first half cell)

32

(first) outer retaining ring (for first half cell)

33

(second) inner retaining ring (for second half cell)

34

(second) outer retaining ring (for second half cell)

35

axis of symmetry

38

Coating (the retaining rings for the first half-cell)

39

Coating (the retaining ring for second half-cell)

4

second half cell

41

(second) hollow fiber membrane

42

(porous) (second) electrode

43

(second) pantograph

44

(second) power connector

45

internal electrolyte inlet / outlet (for second electrolyte)

46

outer electrolyte inlet / outlet (for second electrolyte)

47

liquid-permeable structure

5

Electrolyte (the first half-cell)

51

(first) electrolyte circuit

52

(first) electrolyte reservoir

53

pump

6

Electrolyte (the second half-cell)

61

(second) electrolyte circuit

62

(second) electrolyte reservoir

63

pump

7

Redox Flow Battery (RFB)

71

Stack housing (for screwing several RFCs)

8th

power connection

81

(flat) connection contact

82

Contact insulator

83

Contact bridge

84

conducting salt

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2011/161072 A1 [0003]
• US 2013/0288153 A1 [0004]
• WO 2015/035427 A1 [0005]
• WO 2015/007382 A1 [0006]
• WO 2015/074764 A1 [0006]
• DE 102007034700 A1 [0007]

Cited non-patent literature

• Zheng et al. in: Journal of Power Sources 277 (2015) pp. 104-109 [0007]
• J. Noack et al., In: Angew. Chem. Int. Ed. 2015, 54, 9776-9809, or J. Winsberg et al., In: Angew. Chem. Int. Ed. 2016, DOI: 10.1002 / anie.201604925R1 [0048]

Claims (24)

Redox flow battery for storing electrical energy, comprising at least one redox flow cell as a reaction cell with chambers as polarity-specific half-cells (2, 4) for each electrolyte (5, 6), catholyte or anolyte separated by at least one membrane and each having an electrolyte reservoir (52, 62) are in communication, wherein a first and a second of the polarity-specific half-cells (2, 4) each with an electrolyte (5, 6) of at least one redox-active component, at least partially in substance or dissolved in a solvent and dissolved therein conductive salts, flows through and the electrolytes (5, 6) each with a pumping means (53, 63) are circulated, wherein the membrane as an interface to prevent mixing or electrochemical reactions of the redox-active components with each other and for charge carrier exchange is provided between the half-cells (2, 4), characterized in that - at least the e polarity-specific half cell (2) is formed from a plurality of hollow fiber membranes (21) radially supported by inner and outer concentric retaining rings (31, 32) internally provided with a liquid-permeable electrode (22) and the inner and outer retaining rings (31, 32) have piercing ends, which are connected to a first electrolyte reservoir (52), so that the hollow fiber membranes (21) through the first electrolyte reservoir (52) with a first electrolyte (5) are flowed through, - at least one of the hollow fiber membranes (21 ) chamber surrounding the first half cell (2) formed between the concentric retaining rings (31, 32) is filled with a liquid permeable structure (47) and an electrolytic liquid having at least one conductive salt in solution, and - the second polarity specific half cell (4) by a second electrolyte (6) flows through and with the second electr wherein the second electrolyte (6) is in communication with the first half-cell (2) via the liquid-permeable structure (47) and at least separated by the hollow-fiber membranes (21) of the first half-cell (2). Arrangement according to Claim 1 , characterized in that the chamber surrounding the hollow-fiber membranes (21) of the first polarity-specific half-cell (2) is formed as a second polarity-specific half-cell (4), the liquid-permeable structure (47) being designed to be electrically conductive as a second electrode (42) and via a second Current collector (43) with a power connection (8), on the other hand via first current collector (23) with the first electrodes (22) of the first half-cell (2) in electrical contact is connected, as well as by the second electrolyte (6) flows through and with the second electrolyte reservoir (62) is coupled. Arrangement according to Claim 1 , characterized in that a further number of hollow fiber membranes (41) supported radially by two further concentric retaining rings (33, 34) are concentrically and identically structured with the liquid-permeable electrode (42) concentric with the hollow-fiber membranes (21) of the first half-cell (2) ) within which the hollow-fiber membranes (21) of the first half-cell (2) surrounding liquid-permeable structure (47) are embedded, as the second half-cell (4) is formed, wherein the liquid-permeable structure (47) by means of the Leitsalzlösung contained therein (84) of at least a conductive salt in solution for generating an electrical connection between the first hollow fiber membranes (21) of the first half cell (2) and the second hollow fiber membranes (41) of the second half cell (4) is formed. Arrangement according to Claim 3 , characterized in that the hollow fiber membranes (21) of the first half cell (2) and hollow fiber membranes (41) of the second half cell (4) are each arranged alternately radially within a plane, wherein the first inner retaining ring (31) and the first outer retaining ring (31). 32) of the first half cell (2) are pierced only by the second hollow fiber membranes (41) and the second inner retaining ring (33) of larger diameter than the first inner retaining ring (31) and the second outer retaining ring (34) with a smaller diameter than the first outer retaining ring (32) of the second hollow fiber membranes (41) being pierced alternately with the first hollow fiber membranes (21) and interposed between the first and second inner retaining rings (31, 33) and the first and second outer retaining rings (32, 32; 34) existing annular gaps as inner and outer electrolyte in - / - outlets (45, 46) for the second electrolyte (6) of the second half-cell (4) and the flow de an inner electrolyte inlet / outlet (25) within the first inner retaining ring (31) and an outer electrolyte inlet / outlet (26) external to the first outer retaining ring (32), the first hollow fiber membranes (21) having the first electrolyte (5) are provided. Arrangement according to one of Claims 1 to 4 , characterized in that the hollow fiber membranes (21, 41) are formed as ion-selective membranes and act as interfaces according to the principle of an ion-type exclusion. Arrangement according to one of Claims 1 to 4 , characterized in that the hollow fiber membranes (21, 41) are formed as size exclusion membranes and act as interfaces according to the principle of molecular size exclusion. Arrangement according to one of Claims 1 to 6 , characterized in that the electrodes (22, 42) in the interior of each hollow fiber membrane (21, 41) are formed by an electrically conductive, liquid-permeable filling material, in which a wire or rod-shaped electrically conductive current collector (23, 43) is introduced. Arrangement according to one of Claims 2 and 5 to 7 , characterized in that the second current collector (43) of the second half-cell (4) is applied on the outside of each of the hollow-fiber membranes (21) of the first half-cell (2) as a coating, which with an outer end to an electrically conductive framework or an electrically conductive Housing wall is contacted. order according to one of the Claims 3 to 7 , characterized in that in the first hollow-fiber membranes (21) of the first half-cell (2) and in the second hollow-fiber membranes (41) of the second half-cell (4), the first electrode (22) and the second electrode (42) each inside as a porous, applied electrically conductive coatings and the ends of the hollow fiber membranes (21; 41) are fitted on current collector (23; 43) in the form of electrically conductive tubes or clamping sleeves. Arrangement according to one of Claims 3 to 7 and 9 , characterized in that in the first hollow-fiber membranes (21) of the first half-cell (2) and in the second hollow-fiber membranes (41) of the second half-cell (4) each electrically conductive current collector (23; 43) with an enlarged surface at the same time as electrodes (22; 42) are formed in the interior of the hollow-fiber membranes (21; 41) and, after belonging to the first or second half-cell (2; 4), are guided outwards in a combined manner. Arrangement according to one of Claims 2 to 10 , characterized in that the current collectors (23; 43) are rectilinearly aligned and formed with a roughened or porous surface or helically shaped or wound up. Arrangement according to one of Claims 1 to 11 Characterized in that at least the first hollow-fiber membranes (21) and existing at its radial mounting concentric inner and outer retaining rings (31, 32) and between the concentric retainer rings (31, 32) located liquid permeable structure (47) along each disc-shaped Redox -Flow cell modules (11) form in the form of flat cylinders, which can be stacked in any number of variable RFC module stacks (12) to form a freely scalable redox flow cell (1). Arrangement according to Claim 12 , characterized in that the disc-shaped redox flow cell modules (11) are stacked in a tubular module housing (13), wherein in the resulting RFC module stack (12) the first and second half-cells (2; 4) polarity-specific electrically coupled in parallel and hydrodynamically also linked in parallel and form a modular redox flow cell (1). Arrangement according to Claim 13 , characterized in that the tubular module housing (13) at least of an electrically insulating outer housing tube (132), which in the upper and lower regions each have an upper and a lower housing cap (133, 134) for closing the module housing (13). Arrangement according to Claim 14 , characterized in that the module housing (13) of the redox flow cell (1) consists of two concentric electrically insulating housing tubes, a housing inner tube (131) and the housing outer tube (132), in the upper and in the lower area of the upper housing cap ( 133) and the lower housing cap (134) for closing the module housing (13). Arrangement according to Claim 14 or 15 , characterized in that at least partially in the upper and the lower region of at least the housing outer tube (132) has a thread into which for closing the module housing (13), the upper and lower housing cap (133, 134) with matching threads screwed are. Arrangement according to one of Claims 14 to 16 , characterized in that the housing caps (133, 134) of the tubular module housing (13) of the redox flow cell (1) areally formed, electrically conductive power supply terminals (24, 44) as areal connection contacts (81) on one end face of the housing caps (133, 134), wherein the power terminal (24) of the upper housing cap (133) is in electrical contact with the first current collector (23) of the first half cell (2) and the power terminal (44) of the lower housing cap (134) with the Current collector (43) of the second half-cell (4) is in electrical contact and both power supply terminals (24, 44) each with respect to the other current collector (43; 23) of the other half-cell (4; 2) by contact insulators (82) are electrically insulated. Arrangement according to one of Claims 14 to 17 , characterized in that at least in the housing outer tube (132) of the tubular module housing (13) an electrolyte inlet and an electrolyte outlet (25; 26) for the first electrolyte (5) of first half cell (2) and an electrolyte inlet and an electrolyte outlet (45, 46) for the electrolyte (6) of the second half-cell (4) are used. Arrangement according to one of Claims 14 to 18 characterized in that the upper housing cap (133) has at least one inner electrolyte inlet / outlet (25) for the electrolyte (5) of the first half cell (2) and an inner electrolyte inlet / outlet (45) for the electrolyte (6 ) of the second half cell (4) and in the lower housing cap (134) at least one outer electrolyte inlet / outlet (26) for the electrolyte (5) of the first half cell (2) and an outer electrolyte inlet / outlet (46) for the electrolyte (6) of the second half-cell (4) is provided. Arrangement according to one of Claims 14 to 19 , characterized in that the redox flow cell (1) with face-mounted, flat terminal contacts (81) of the electrically insulating tubular module housing (13) is concentrically surrounded and fixed therein, wherein both on an outer and on an inner side a housing tube (131 132) at least in sections each have a thread (135) is formed so that a plurality of tubular redox flow cells (1) are screwed together to form an RFC stack. Arrangement according to one of Claims 12 to 20 , characterized in that a plurality of redox flow cells (1) with symmetry axes (35) oriented parallel to one another as single or already collinearly stacked redox flow cells (1) in the redox flow battery (7) in a or multi-layer arrangement are combined, wherein the redox flow cells (1) by means of contact bridges (83) or face-side terminal contacts (81) with oppositely poled, first and second power connection terminals (24, 44) connected in an electrical series circuit and by connecting the first and second half-cells (2, 4) are interconnected in respective common electrolyte circuits (51, 61) as hydrodynamic parallel connection Arrangement according to one of Claims 12 to 21 , characterized in that at least one tubular redox flow cell (1) has two electrolyte reservoirs (52, 62) arranged concentrically with one another and with the first and second half cells (2; Arrangement according to Claim 22 characterized in that a plurality of the tubular redox flow cells (1) stacked adjacent to one another in the axial direction are arranged concentrically to the two concentrically shaped electrolyte reservoirs (52, 62), the first and second half cells (2, 4) being different Redox flow cells (1) via a respective at least one pump (53, 63) containing electrolyte circuit (51, 61) with one of the concentrically arranged electrolyte reservoirs (52, 62) hydrodynamically connected in parallel and electrically connected in a series circuit. Arrangement according to one of Claims 12 to 23 , characterized in that several of the redox flow batteries (7) with parallel aligned axes of symmetry (35) of the concentric redox flow cells (1) assembled in a single or multi-layer arrangement, in a hydrodynamic parallel connection with at least partially shared Electrolyte reservoirs (52, 62) are connected and at least partially linked together in an electrical parallel circuit.

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