End plate for a cell stack of a redox flow battery

Abstract

The aim of the invention is to provide an end plate (100) for a cell stack (10) of a redox flow battery (1), said end plate having a higher degree of mechanical and chemical resistance than the known prior art. This is achieved in that a press component (A) is provided for pressing half cells (2a, 2b) stacked in the cell stack (10) of the redox flow battery (1) against each other, and at least one channel component (B) is provided which forms at least one flow channel (K) for supplying or discharging electrolyte liquid (15a, 15b) into or out of the cell stack (10) of the redox flow battery (1), wherein the press component (A) contacts the channel component (B) outside of the flow channel (K) in order to fix the channel component (B) against the press component (A), the channel component (B) is made of an acid-resistant channel plastic, and the press component (A) is made of a press plastic which differs from the channel plastic, said press plastic having a modulus of elasticity of at least 7500 MPa.

Description

[0001] End plate for a cell stack of a redox flow battery

[0002] The present invention relates to an end plate for a cell stack of a redox flow battery, which comprises a press component for pressing together half-cells stacked in the cell stack of the redox flow battery, as well as at least one channel component forming at least one flow channel for supplying or discharging electrolyte fluid into the cell stack of the redox flow battery, wherein the press component contacts the channel component outside the flow channel to fix the channel component to the press component. Furthermore, the invention relates to a method for producing an end plate for a redox flow battery.

[0003] Redox flow batteries are known from the prior art, e.g. from the documents AT 501 902 B1, AT 510 723 B1 or WO 2023 / 110799 A1. A redox flow battery is, in a known manner, an electrochemically based energy storage device which comprises storage tanks for storing electrolyte liquids with different electrical charges, e.g. electrically positively and electrically negatively charged, as well as pumps and lines for circulating the electrolyte liquids (electrolytes) through one or more cell stacks, each of which has a number of individual electrochemical cells. The individual cells of the cell stack are each formed by a positive half-cell and a negative half-cell arranged side by side, with the positive and negative half-cells of an individual cell being separated from one another by a semipermeable membrane, typically an ion exchange membrane.The semipermeable membrane is, for example, a cation and / or anion exchange membrane, e.g., Nation®. The positive half-cell contains a positive electrode located in a frame through which the positive electrolyte flows. The negative half-cell contains a negative electrode located in a frame through which the negative electrolyte flows. The positive and negative electrolytes are circulated separately through the half-cells. The positive and negative electrodes are usually made of porous graphite felts through which the respective electrolyte flows.

[0004] The half-cell frames are arranged side by side, and the resulting individual cells are connected to form a cell stack, alternating between negative and positive half-cells. Electrically conductive electrode plates, such as bipolar plates, are arranged between adjacent individual cells of the cell stack as current collectors. These plates are usually made of a composite material made of carbon and plastic. Current collectors, preferably metallic, are located on the electrode plates on the axial outer sides of the axially outer individual cells of the cell stack. These current collectors provide an electrical contact to the outside, allowing an electrical voltage to be tapped across the entire cell stack (discharging the redox flow battery) or to be applied to the cell stack (charging the redox flow battery).The cell stack is closed off on each axial outer side by an end plate, which holds the cell stack together. Bolts are typically inserted through the end plates, and the end plates are pressed together onto the bolts by nuts. The nuts on at least one side are usually preloaded by a spring to compensate for any settling of the half-cell frames.

[0005] In the widely used embodiment as a vanadium-based redox flow battery, the positive electrolyte fluid in the charged state consists of a redox pair in the form of vanadium with the oxidation number +4 (also known as V lv or V 4+ and vanadium with the oxidation number +5 (also known as V v or V 5+ The negative electrolyte fluid in the charged state consists of a redox pair in the form of vanadium with the oxidation number +2 (also known as V" or V 2+referred to) and vanadium with the oxidation number +3 (also known as V 111 or V 3+ Redox flow batteries are also known based on other redox pairs, for example, those based on the chemical elements Br, S, Fe, Ti, Mn, Cr, or organic compounds such as ferricyanide or quinone, all of which operate essentially according to the same principle.

[0006] The end plates (pressure plates) of a cell stack in a redox flow battery not only compress the cell stack but also primarily serve the function of conveying the vanadium electrolyte fluid into and out of the cell stack via inflow channels. This places high demands on the chemical and electrochemical stability, temperature stability, pressure stability, and general mechanical strength of the materials used in the end plates. Another key function of an end plate is to keep the interior of the stack compressed as evenly as possible, particularly to minimize bending of the frames of the individual cells and any possible bulging of components arranged within the frames (felt, bipolar plates, etc.).The end plates are also intended to exert sufficient contact pressure on the individual cells between them in order to seal the individual cells in the cell stack against the leakage of electrolyte fluid or the mixing of electrolyte fluid within the cell stack. In addition, end plates are often required to be electrically insulating, to accommodate both current collectors and power connections, and to exhibit a high degree of tightness in the area around the inflow channels against the incoming and outgoing electrolyte fluids. This multitude of tasks that an end plate must fulfill regularly leads to difficulties in its practical implementation. Although the problem of manufacturing suitable end plates for cell stacks of redox flow batteries is known in the state of the art, no fully satisfactory solutions have been published to date.For example, US 2023 / 0020332 A1 shows an injection-molding-based method for manufacturing a cell frame for a vanadium redox flow battery. However, US 2023 / 0020332 A1 does not address the fact that different areas of an end plate may sometimes have to perform entirely different tasks.

[0007] It is therefore an object of the present invention to provide an end plate for a cell stack of a redox flow battery which is mechanically and chemically more stable and denser than the known prior art, but can nevertheless be produced efficiently and cost-effectively.

[0008] According to the invention, in order to achieve this object, for an end plate mentioned at the outset, the channel component is to be manufactured from an acid-resistant channel plastic and the press component is to be manufactured from a press plastic different from the channel plastic, wherein the press plastic has a modulus of elasticity of at least 7500 MPa.

[0009] The present invention thus provides for the use of two different materials for at least two different components of an end plate, each of which can be optimized to solve different tasks of the end plate. In particular, the invention thus allows for the pressed component to be provided with a pressed plastic tailored to ensuring high mechanical strength, e.g., a composite material with polypropylene (PP) as the base material and glass fibers as the reinforcing phase or another reinforced plastic, while for the channel component, in contrast, a material optimized with regard to electrolyte resistance can be used. The channel plastic can, in particular, have a significantly lower modulus of elasticity of less than 4000 MPa, less than 3000 MPa, or less than 2500 MPa.

[0010] With regard to the specific selection of the channel and molded plastic, as well as with regard to the specific design of the interaction between the channel component and the molded component, the present invention offers great flexibility, allowing precise adaptation to the respective requirements depending on the application. Specifically, it can be provided that the molded component and the channel component are connected to one another in a material-to-material and / or force-fitting and / or form-fitting manner, or it can be provided that the molded plastic is selected as a composite material comprising a thermoplastic material phase, preferably polypropylene (PP) or polyethylene (PE) or polyvinyl chloride (PVC) or polyvinylidene fluoride (PVDF), and a reinforcing material, preferably glass fibers or carbon fibers, or that the channel plastic is selected as polypropylene (PP) or polyethylene (PE) or polyvinyl chloride (PVC) or polyvinylidene fluoride (PVDF).Preferably, the molded plastic and the channel plastic are electrically non-conductive materials in order to ensure electrical insulation from the current-carrying components of a cell stack.

[0011] In further advantageous embodiments, in particular the material parameters of the molded plastic and the channel plastic can be matched to one another, for example by selecting a molded plastic whose melting point approximately corresponds to the melting point of the channel plastic, or whose melting point deviates from a melting point of the channel plastic by less than 10% or by less than 5% or by less than 1%, and / or by selecting a molded plastic which has a thermal expansion coefficient which deviates from a thermal expansion coefficient of the channel plastic by less than 20% or by less than 10% or by less than 5%, so that deformation or delamination of the end plate 100 due to temperature effects during operation of a redox flow battery 1 is largely prevented.

[0012] Likewise, at least one current collector recess for accommodating a current collector of a cell stack of a redox flow battery can be provided in the press component, and one end of the flow channel formed by the channel component can be designed as a hose nozzle or a plug-in connection for supplying and / or discharging an electrolyte fluid into a cell stack of a redox flow battery. This makes it particularly simple and efficient to construct a redox flow battery using an end plate according to the invention.A redox flow battery constructed by means of an end plate according to the invention typically comprises a cell stack made up of a plurality of half-cells stacked in a stack direction, each of which can be framed by a frame, wherein the cell stack is pressed and held together by means of two end plates according to the invention, and wherein a contact force is applied to the end plate by at least one clamping means.

[0013] Furthermore, the stated object is achieved by a method for producing an end plate for a cell stack of a redox flow battery, in which method it is provided to prefabricate the at least one channel component from an acid-resistant channel plastic, to place the channel component on a mandrel, to attach a press component mold receiving the channel component placed on the mandrel, wherein the press component mold is open to the channel component at least in sections, to injection mold a press plastic different from the channel plastic and having a modulus of elasticity of at least 7500 MPa into the press component mold to produce the press component, wherein the press plastic at least partially encapsulates the prefabricated channel component through the at least section-wise openings of the press component mold.In this way, it is not only possible to produce the end plate according to the invention efficiently and cost-effectively by means of injection molding, but also to create a particularly stable and robust connection between the channel component and the press component by overmolding the channel component with the molded plastic.

[0014] The present invention will be explained in more detail below with reference to Figures 1 to 9, which show exemplary, schematic and non-limiting advantageous embodiments of the invention.

[0015] Fig.1 the basic operating principle of a redox flow battery,

[0016] Fig.2 a cell stack of a redox flow battery,

[0017] Fig.3 shows the structure of a cell stack of a redox flow battery,

[0018] Fig.4 an embodiment of an end plate according to the invention,

[0019] Fig.5 a channel component according to the invention,

[0020] Fig.6-9 further embodiments of an end plate according to the invention.

[0021] Fig. 1 shows a schematic structure of a redox flow battery 1 using a single cell 2 of a cell stack 10 to explain the well-known functional principle of a redox flow battery 1. For better explanation and illustration, only a single cell 2 of a cell stack 10 of a redox flow battery 1 is shown in Fig. 1, whereby a cell stack 10 will generally have a plurality of single cells 2.

[0022] A single cell 2 consists of two half-cells 2a, 2b, which form a positive reaction chamber 3a and a negative reaction chamber 3b. The two half-cells 2a, 2b, or the positive reaction chamber 3a and the negative reaction chamber 3b, are separated by a semipermeable, in particular ion-selective, membrane 4. The reaction chambers 3a, 3b are formed, for example, in recesses 6a, 6b of frames 5a, 5b. An electrode 7a, 7b is arranged in each of the reaction chambers 3a, 3b and in the recesses 6a, 6b. Electrolyte fluids 15a, 15b with different electrical charges (positive and negative electrolyte fluids) flow through the recesses 6a, 6b and the electrodes 7a, 7b arranged therein of a single cell 2. Each of the electrolyte liquids 15a, 15b contains a redox pair with specific, time-varying concentrations (depending on the state of charge) of redox elements.The semipermeable, particularly ion-selective, membrane 4 can be made, for example, of sulfonate-modified polytetrafluoroethylene (PTFE), with the trade name Nation™, and enables ions to achieve charge equalization between the positive reaction chamber 3a and the negative reaction chamber 3b (or between the electrolyte liquids 15a, 15b contained therein). The individual cell 2 is closed on both sides by an electrode plate 8. A redox flow battery 1 also includes power connections 11, 12 for tapping an electrical cell stack voltage Vz applied to the cell stack 10 via a consumer 14 (discharging the redox flow battery 1) or for applying an electrical cell stack voltage Vz to the cell stack 10 (charging the redox flow battery 1).

[0023] An electrical load 14 can take any form. Based on the voltage, current, or power requirements of the electrical load 14, a cell stack 10 can be configured in a redox flow battery 1 to provide the necessary electrical voltage and / or the necessary electrical current. Redox flow batteries 1 are often used as stationary energy storage devices, for example, to serve as emergency power systems for industrial plants, storage systems for renewable energy (photovoltaics, wind power), and the like. Consequently, depending on the application, a person skilled in the art can design a cell stack 10, or a parallel and / or serial connection of several cell stacks, and redox pairs in a redox flow battery 1.

[0024] The electrolyte fluids 15a, 15b are stored in storage tanks 13a, 13b and are circulated from there through the cell stack 10 by means of circulation pumps 9a, 9b, specifically through a half-cell 2a, 2b of a single cell 2 of the cell stack 10. For this purpose, a supply line 16a, 16b and a discharge line 17a, 17b are provided for each electrolyte fluid 15a, 15b, which are connected via electrolyte fluid connections 22a, 22b, 23a, 23b to associated electrolyte fluid channels 18a, 18b, 19a, 19b (see Figs. 2 and 3) in the cell stack 10.

[0025] In a cell stack 10 with several adjacent individual cells 2, an electrode plate 8, such as a bipolar plate, is arranged between each two adjacent individual cells 2. At the outer ends of the cell stack 10, a power connection 11, 12 can be located on the outer electrode plates 8 or on the outer half-cells 2a, 2b (or electrodes 7a, 7b) of the cell stack 10, which can be electrically contacted from the outside.

[0026] The typical structure of a cell stack 10 of a redox flow battery 1 is explained in more detail with reference to Figs.2 and 3.

[0027] A cell stack 10 of a redox flow battery 1 comprises at least one individual cell 2, generally a plurality of individual cells 2, which in turn are each formed from two frames 5a, 5b. A frame 5a, 5b is preferably made of a plastic, such as an elastomer, such as a polyolefinic thermoplastic elastomer (TPE or TPO), such as Santoprene®, or a thermoplastic vulcanate (TPV), in particular using an injection molding process. In the stack direction R, between two frames 5a, 5b of an individual cell 2, a semipermeable membrane 4, typically an ion exchange membrane (either a cation or anion exchange membrane, e.g. Nation®), is arranged in the cell stack 10. The membrane 4 separates the reaction spaces 3a, 3b, recesses 6a, 6b of the half-cells 2a, 2b of a single cell 2, the electrodes 7a, 7b arranged therein and the electrolyte liquids 15a, 15b located therein.An electrode plate 8, e.g., a bipolar plate, is arranged between each two adjacent individual cells 2 in the stack direction R in the cell stack 10. The electrode plate 8 is inserted, as shown in Fig. 3, into mutually facing recesses 40 in the frames 5a, 5b. The frames 5a, 5b have central recesses 6a, 6b extending in the stack direction R, each of which forms a reaction chamber 3a, 3b and in which electrodes 7a, 7b, e.g., carbon fiber mats, are arranged, as shown in Fig. 3.

[0028] The differently charged electrolyte fluids 15a, 15b are pumped through the recesses 6a, 6b in the frames 5a, 5b through the individual cells 2, with an electrolyte fluid 15a, 15b with a different electrical charge flowing through the electrode 7a, 7b of each half-cell 2a, 2b of an individual cell 2. The electrolyte fluids 15a, 15b are supplied and discharged from the outside via electrolyte fluid connections 22a, 22b, 23a, 23b and are then distributed internally via an electrolyte fluid channel system provided in the frames 5a, 5b with electrolyte fluid channels 18a, 18b, 19a, 19b, as explained in more detail below. The electrolyte fluid connections 22a, 22b, 23a, 23b are provided, for example, on an end plate 100 of the cell stack 10, as shown in Fig.3, although other arrangements of the electrolyte fluid connections 22a, 22b, 23a, 23b, for example on an end frame 20, are also possible.

[0029] The cell stack 10 can be closed off in the stacking direction R by an end frame 20 at each of its two axial ends. An electrically conductive current collector 21 is arranged in the end frame 20, e.g., in a recess on one end face of the end frame 20, and is connected to an externally routed electrical power connection 11, 12. In the illustrated embodiment, the current collector 21 rests against the last electrode plate 8 of the last individual cell 2 to establish electrical contact. However, the current collector 21 or a power connection 11, 12 could also be designed differently. Likewise, the end frame 20 could be omitted from the cell stack 10.

[0030] In the illustrated embodiment, the cell stack 10 is arranged between two end plates 100 and pressed together by clamping means 25. The clamping means 25 are designed, for example, with through-passing bolts 26, nuts 27, washers 28, and springs 29, as shown in Fig. 2. With the aid of the clamping means, contact forces acting in opposite directions are applied to the end plates 100 provided in Fig. 2, which compress the cell stack. However, the cell stack 10 can also be held together in other ways; in particular, the clamping means 25 can be designed differently. To prevent the frames 5a, 5b from settling due to the contact pressure of the clamping means 25, a spacer 31 can also be provided between the end plates 100.

[0031] As previously stated, it is particularly important for a redox flow battery 1 that the end plates 100 in particular meet a series of requirements, primarily regarding their chemical resistance, their temperature and pressure stability, their tightness, and their mechanical strength. Obviously, for example, those areas of an end plate 100 on which the contact forces applied by means of clamping devices 25 act must be mechanically resistant. The end plate 100 should also be mechanically stable and deform only negligibly due to the contact forces. On the other hand, it is necessary that those areas in which the electrolyte fluid connections 22a, 22b, 23a, 23b run have a high chemical resistance in order to avoid being attacked by the electrolyte fluids 15a, 15b.Furthermore, strict requirements apply to the tightness of the areas around the electrolyte fluid connections 22a, 22b, 23a, 23b, in particular to prevent electrolyte fluid 15a, 15b from reaching the power connections 11, 12 due to leakage and causing damage there, in particular through corrosion.

[0032] In the known prior art, end plates 100 were preferably manufactured by milling from a material blank. In view of the aforementioned requirements, however, it is easy to see that simply determining a material suitable for milling that meets the aforementioned boundary conditions often represents a difficult task. Such end plates, often metallic, always require additional electrical insulation from the cell stack 10 and / or the current collector 21 and / or a power connection 11, 12, which makes the construction of a cell stack 10 of the redox flow battery 1 more complex and requires additional components.

[0033] In order to meet the above requirements more simply, reliably and cost-effectively, an end plate 100 is proposed within the scope of this invention, which end plate has a press component A for pressing together, preferably with the aid of clamping means 25, half-cells 2a, 2b (i.e., the cell stack 10) arranged in a stack in the cell stack 10 of the redox flow battery 1, and at least one channel component B forming at least one flow channel K for supplying and / or discharging electrolyte liquid 15a, 15b into the redox flow battery 1. To fix the channel component B to the press component A, the press component A touches the channel component B outside the flow channel K.

[0034] According to the invention, the channel component B is made of an acid-resistant channel plastic and the press component A is made of a press plastic different from the channel plastic, wherein the press plastic has a modulus of elasticity of at least 7500MPa.

[0035] In essence, the present invention provides for the use of two different materials for at least two different components of an end plate 100, each of which is used to solve different tasks of the end plate 100. The invention allows for the press component A to be provided with a press-molded plastic that is tailored to ensure high mechanical strength, e.g., a composite material with polypropylene (PP) as the base material and glass fibers as the reinforcing phase or another reinforced plastic. The press-molded plastic should have a minimum elastic modulus of at least 7500 MPa, or at least 8000 MPa, or at least 8300 MPa, in order to ensure the required mechanical strength of the end plate 100. For the channel component B, in contrast, an acid-resistant channel plastic can be used, e.g.,a thermoplastic based on polyethylene (PE), polypropylene (PP) or polyvinyl chloride (PVC). The acid resistance is necessary because the electrolyte liquids 15a, 15b contain acid, such as sulfuric acid. Thermoplastics with a high degree of purity are preferably used for the production of channel component B, i.e. the thermoplastic contains only a small proportion of foreign material in addition to a base material (such as PE, PP, PVC, PVDF, etc.), e.g., in addition to PP, only a maximum of 10% by volume of foreign materials, or a maximum of 5% by volume of foreign materials, or a maximum of 1% by volume of foreign materials. In certain applications, foreign materials can be deliberately added as additives to improve certain properties of the channel plastic, such as processability on an injection molding system.

[0036] In approaches known from the prior art, in which end plates 100 are typically milled from a single material blank, in contrast to the invention, a targeted coordination of selected areas to achieve certain specifications is not possible. In the case of the milling of an end plate 100 from a single material blank, as is known from the prior art, it is important to assign both the required chemical properties and the required mechanical properties to the entire component, i.e. the entire end plate 100. This limits the amount of materials that can be used for obvious reasons, thus typically causing higher costs and ultimately, due to a necessary compromise between chemical and mechanical properties, often also leading to a less satisfactory end plate 100 overall.

[0037] Regarding the chemical resistance of the channel component B, which is in direct contact with an electrolyte liquid 15a, 15b, in the present case, the acid resistance is of particular importance, essentially due to the fact that the electrolyte liquids 15a, 15b used in redox flow batteries 1, e.g. vanadium electrolyte liquid V lv , V v, are typically strongly acidic liquids, usually with pH values ​​in the range of 1. Acid resistance in the present context is to be understood as the property of a material not to form compounds with an acid, nor to be attacked or dissolved by it, even at high temperatures. In a known manner, it is difficult to combine the material properties of acid resistance and mechanical strength in one component. The chemically resistant material, ie the channel plastic, can, however, be limited within the scope of the invention to the absolutely necessary area of ​​the end plate 100, specifically the channel component B, which significantly simplifies the design and construction of an end plate 100. It is advantageous to use the predominant part, ie, for example85% or 90% or 95% of the volume of an end plate 100 as press component A, and only the part of the volume of an end plate 100 required to provide the flow channels K as channel component B in order to achieve the highest possible mechanical strength.

[0038] In the course of the invention, it was recognized in this context that sufficient mechanical strength can be ensured if the elastic modulus of the molded plastic used to manufacture the molded component A is at least 7500 MPa. By using different materials, plastics with significantly lower strength values ​​than those of the molded plastic can be used for the channel component B, e.g., lower by a factor of 2, or by a factor of 5, or by a factor of 10, so that the channel component B, for example, has an elastic modulus of less than 4000 MPa, or less than 3000 MPa, or less than 2500 MPa.

[0039] In the context of this invention, the modulus of elasticity is determined by means of a tensile test in accordance with the ISO 527 standard, in the version valid on October 1, 2023.

[0040] In contrast to common stack concepts, which, among other things, use metal plates as additional components for pressing cell stacks in an end plate 100 and therefore require a further insulation layer, e.g. an insulation plate, to insulate the metal plate from the electrical components of the cell stack 10 of the redox flow battery 1 already mentioned several times, the functions of insulation and pressing can be combined in the present invention, in particular if electrically non-conductive materials are used for the molded plastic and for the channel plastic.Since in principle no further components need to be provided in an end plate 100 according to the invention besides the press component A and the at least one channel component B, in addition to the advantages already explained, a reduction in the component weight is also achieved, which allows simpler and easier handling, especially during the assembly of a cell stack 10.

[0041] According to the invention, the press component A at least partially touches the channel component B outside the flow channel K in order to fix the channel component B to the press component A. As a result of the contact, relative movements between the press component A and the channel component B during operation of a redox flow battery 1 are advantageously at least largely prevented. As will be explained in more detail later, there is flexibility in the implementation in this regard in particular. Specifically, the press component A and the channel component B can be connected to one another by means of the contact in a materially bonded and / or force-fitting and / or form-fitting manner, which can be achieved, for example, by an adhesive connection, a snap connection, a plug-in connection, a welded connection or combinations of these connections, etc.In a particularly advantageous manner, a material-to-material connection between a press-molded component A according to the invention and a channel component B according to the invention can be achieved within the framework of an injection-molding process, wherein the prefabricated channel component B is overmolded with molded plastic during the injection-molding of the press component A. This will be discussed separately later. The contact does not have to cover the entire surface of the channel component B. The channel component B is held to the press component A by means of the contact.

[0042] A first, concrete design option for an end plate 100 according to the invention is shown in Figures 4 and 5. The end plate 100 according to Figure 4 comprises a press component A according to the above explanations, i.e., made of a molded plastic with a modulus of elasticity of at least 7500 MPa to ensure the required mechanical strength. The aforementioned clamping means 25 can be attached to the corners A1, A2, A3, A4 of the end plate 100, or distributed over the circumference of the end plate 100, in order to apply the required contact forces. In principle, however, other locations for attaching the clamping means 25 are also conceivable; the specific choice of corners A1, A2, A3, A4 is therefore by no means to be understood as limiting. In addition to the press component A, the specific end plate 100 has two channel components Ba, Bb facing away from one another, which, according to the above explanations, form two flow channels Ka, Kb.The channel components Ba, Bb of the end plate 100 according to Fig. 4 are designed as simply angled tubes, as can be seen particularly in the sectional view of the individual channel component Bb in Fig. 5. The channel components Ba, Bb are designed to connect storage tanks 13a, 13b for electrolyte supply and removal with the internal fluid distribution of a cell stack 10 of a redox flow battery 1. The channel components Ba, Bb are attached to the side of the end plate 100 that faces away from the cell stack 10 arranged between two end plates when the end plates 100 and cell stack 10 are assembled.In a particularly advantageous manner, the ends of the flow channels K formed by the channel components B facing the storage tanks 13a, 13b can be designed directly as a connection, for example as a hose nozzle or as a plug-in connection, for connecting lines 16a, 16b, 17a, 17b carrying electrolyte liquids 15a, 15b, which no longer requires the separate attachment of such connection means in a separate work step, e.g. by welding or gluing.

[0043] It should be noted that the angled design of the channel components Ba, Bb is in no way to be understood as restrictive. In particular, the channel components Ba, Bb can also be designed not at all, singly, or multiply. The two channel components Ba, Bb do not necessarily have to be designed identically. As will be shown below using a series of alternative designs of an end plate 100 according to the invention (Figs. 6-9), the invention also offers design freedom and flexibility with regard to the other characteristics of the design according to Fig. 4 mentioned, e.g. with regard to the orientation of the channel components Ba, Bb, the connection of the channel components Ba, Bb to the press component A, the design of the press component A, etc. The above and following explanations apply, unless explicitly stated, to all of the implementation variants discussed here.

[0044] When the end plate 100 shown in Fig. 4 is used in a redox flow battery 1, each flow channel Ka, Kb is connected to an electrolyte liquid channel 18a, 18b, 19a, 19b in the cell stack 10. If the end plate 100 according to the invention from Fig. 4 is used in a redox flow battery 1 according to Fig. 2, for example as the upper end plate 100, i.e. in this case arranged closer to the springs 29, the flow channels Ka, Kb correspond to the electrolyte liquid connections 23a, 23b. If the end plate 100 according to the invention from Fig. 4 is used as the lower end plate 100, i.e. in this case further away from the springs 29, the channel channels Ka, Kb correspond to the electrolyte liquid connections 22a, 22b.

[0045] Further embodiments of an end plate 100 according to the invention are shown in Figures 6-9. Figures 6 and 7 show an end plate 100 according to the invention in which the channel components B do not point away from each other as in Figure 4, but are oriented in the same way. The invention offers flexibility with regard to the arrangement of channel components B. Specifically, a significantly larger number of channel components B could also be provided in one end plate, e.g. three or four or five channel components B, e.g. in order to connect a redox flow battery 1 to more than just two storage tanks 13a, 13b if necessary. Another possible alternative embodiment is shown in Figure 8, in which only one channel component B is provided, which is oriented at a right angle to the press component A. Of course, a plurality of channel components B oriented at a right angle to the press component A can also be provided.

[0046] Fig. 9 shows the rear side of an end plate 100, for example the end plate 100 shown in Figs. 6 and 7. When the end plate 100 is used in a redox flow battery 1, the rear side is arranged facing the cell stack 10. Fig. 9 reveals a further important aspect of the present invention, specifically that a current collector recess A-21 for receiving a current collector 21 of a redox flow battery 1 is provided in a particularly advantageous manner in a press component A of an end plate 100 according to the invention. If the press component A and the channel component B are made of electrically non-conductive plastics, there is in particular no further need for additional insulation means.

[0047] As mentioned, compromises between the achievable mechanical and chemical properties are not necessary with an end plate 100 according to the invention, which significantly increases the design flexibility and optimization potential, especially in the design of an end plate 100, but consequently also in the design of a complete cell stack 10 of a redox flow battery 1. Some of the design options resulting from this flexibility are listed below.

[0048] Thus, in an advantageous embodiment of the invention, the material parameters of the molded plastic and the channel plastic can be matched to one another, for example by selecting a molded plastic whose melting point approximately corresponds to the melting point of the channel plastic, or whose melting point deviates from a melting point of the channel plastic by less than 10% or by less than 5% or by less than 1%, and / or by selecting a molded plastic that has a thermal expansion coefficient that deviates from a thermal expansion coefficient of the channel plastic by less than 20% or by less than 10% or by less than 5%, so that deformation or delamination of the end plate 100 due to temperature effects during operation of a redox flow battery 1 is largely prevented.As noted earlier, in order to create a material-to-material connection between the press component A and the channel component B, it is possible, in a particularly advantageous manner, to use an injection molding process in which a prefabricated channel component B is overmolded with molten press plastic during the production of the press component A.

[0049] Specifically, in a first manufacturing step, the channel component B can be prefabricated from the acid-resistant channel plastic, then in a further manufacturing step, the channel component B can be placed in a cavity of the press component mold for the press component A, for example on a mandrel, which cavity is to be at least partially filled with press plastic, and then in a final manufacturing step, the press component A can be manufactured by injection-molding a press plastic different from the channel plastic, which has preferably been heated beforehand in an extrusion screw, into the press component mold, so that the press plastic at least partially encloses the prefabricated channel component B.

[0050] In a particularly advantageous manner, a channel plastic and a molded plastic can be provided that can be bonded together by surface melting. In this way, the (hot) molded plastic can at least partially melt the surface of the channel component B during overmolding, and the molded component A and the channel component B bond together in the melting area to form a melting zone. Specifically, this manufacturing variant results in the channel component B melting, with the molecular chains of the channel component B and the molded component A interlocking. This creates a surface weld of a few tenths of a millimeter across the channel component B.Depending on the local conditions, this creates a local mixing of the molded plastic and the channel plastic, as well as a local transition phase between the molded plastic and the channel plastic. The resulting bond can be strengthened by surface adhesion. Complete melting of the channel component B must, of course, be prevented, which can be achieved through appropriate dimensioning and / or material selection and / or process control and / or cooling in the mandrel during injection molding.

[0051] It should be noted that an end plate 100 according to the invention can be manufactured by injection molding, even without necessarily melting the channel component B. In such a case, in which the melting point of the channel component B is selected to be high enough to avoid melting of the channel component B, a positive connection between the press component A and the channel component B can be formed by overmolding. With the aid of a manufacturing process based on injection molding that corresponds to the above explanations, the manufacturing time and material usage can be significantly reduced in every variant, and yet a durable and dimensionally stable connection between the press component A and the channel component B can be achieved.

Claims

Patent claims 1. End plate (100) for a cell stack (10) of a redox flow battery (1), comprising a press component (A) for pressing together half-cells (2a, 2b) arranged in a stack in the cell stack (10) of the redox flow battery (1), and at least one channel component (B) forming at least one flow channel (K) for supplying or discharging electrolyte liquid (15a, 15b) into the cell stack (10) of the redox flow battery (1), wherein the press component (A) contacts the channel component (B) outside the flow channel (K) for fixing the channel component (B) to the press component (A), characterized in that the channel component (B) is made of an acid-resistant channel plastic and that the press component (A) is made of a press plastic different from the channel plastic, wherein the press plastic has a modulus of elasticity of at least 7500MPa.

2. End plate (100) according to claim 1, characterized in that the press component (A) and the channel component (B) are connected to one another in a materially bonded and / or force-locked and / or form-locked manner.

3. End plate (100) according to one of the preceding claims, characterized in that at least one current collector recess (A-21) for receiving a current collector (21) of a cell stack (10) of a redox flow battery (1) is provided in the press component (A).

4. End plate (100) according to one of the preceding claims, characterized in that one end of the flow channel (K) formed by the channel component (B) is designed as a hose nozzle or as a plug connection for supplying and / or discharging an electrolyte liquid (15a, 15b) into a cell stack (10) of a redox flow battery (1).

5. End plate (100) according to one of the preceding claims, characterized in that the molded plastic is a composite material comprising a thermoplastic material phase, preferably polypropylene (PP) or polyethylene (PE) or polyvinyl chloride (PVC) or polyvinylidene fluoride (PVDF), and a reinforcing material, preferably glass fibers or carbon fibers.

6. End plate (100) according to one of the preceding claims, characterized in that the channel plastic is polypropylene (PP) or polyethylene (PE) or polyvinyl chloride (PVC) or polyvinylidene fluoride (PVDF).

7. End plate (100) according to one of the preceding claims, characterized in that the channel plastic has a modulus of elasticity of less than 4000MPa or less than 3000MPa or less than 2500MPa.

8. End plate (100) according to one of the preceding claims, characterized in that the molded plastic and the channel plastic are electrically non-conductive.

9. End plate (100) according to one of the preceding claims, characterized in that the molded plastic has a melting point which differs from a melting point of the channel plastic by less than 10% or by less than 5% or by less than 1%.

10. End plate (100) according to one of the preceding claims, characterized in that a thermal expansion coefficient of the molded plastic deviates by less than 20% or by less than 10% or by less than 5% from a thermal expansion coefficient of the channel plastic.

11. Redox flow battery (1), comprising a cell stack (10) made of a plurality of half-cells (2a, 2b) stacked in a stack direction (R), wherein the half-cells (2a, 2b) are each framed by a frame (5a, 5b), wherein the cell stack (10) is pressed and held together by means of two end plates (100) according to one of the preceding claims, wherein a contact force is applied to the end plate (100) by at least one clamping means (25).

12. Method for producing an end plate (100) for a cell stack (10) of a redox flow battery (1) with a press component (A) for pressing together half-cells (2a, 2b) arranged in a stack in the cell stack (10) of the redox flow battery (1), and with at least one channel component (B) forming at least one flow channel (K) for supplying or discharging electrolyte fluid (15a, 15b) into the cell stack (10) of the redox flow battery (1), wherein the press component (A) touches the channel component (B) outside the flow channel (K) for fixing the channel component (B) to the press component (A), comprising the steps - Prefabrication of at least one channel component (B) from an acid-resistant sewer plastic, - Place the channel component (B) on a mandrel, - Attaching a press fitting that receives the channel component (B) placed on the mandrel Component mold, wherein the press component mold is at least partially open to the channel component (B), - Injection molding of a press plastic different from the channel plastic with a modulus of elasticity of at least 7500 MPa into the press component mold to produce the press component (A), wherein the press plastic at least partially encloses the prefabricated channel component (B) through the at least section-wise openings of the press component mold.

13. The method according to claim 12, characterized in that the channel component (B) is at least partially melted superficially during the overmolding with the molding plastic, so that the molding component (A) and the channel component (B) bond together in the region of the melting to form a melting zone.

14. The method according to claim 12 or 13, characterized in that the molded plastic is heated in an extrusion screw before injection molding.

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