Redox flow batteries having electrolyte distributors with integrated channels and method of manufacture thereof

Abstract

The present invention discloses a battery formed by at least one cell or cell stack incorporating flow distributors (1) that house the electrodes (3), polymer membranes (5), bipolar plates (4) and current collector plates (7) that are embedded in a resin block (10) that ensures sealing tightness. The present invention further discloses a method for manufacturing said battery.

Description

[0001] REDOX FLOW BATTERIES WITH ELECTROLYTE DISTRIBUTORS WITH INTEGRATED CHANNEL AND MANUFACTURING METHOD THEREOF

[0002] DESCRIPTION

[0003] OBJECT OF THE INVENTION

[0004] The present invention relates to the technical field of redox flow batteries and describes a battery formed by at least one cell or a stack of cells that incorporate flow distributors that house the electrodes, polymeric membranes, bipolar plates and collector plates that are embedded within a resin block that guarantees its tightness, as well as describes a manufacturing method of said battery.

[0005] BACKGROUND OF THE INVENTION

[0006] A redox flow battery (RFB) is a type of rechargeable battery that uses chemical species with different oxidation states to store energy. These chemical species, which are electroactive, are dissolved in a solution known as the electrolyte. Like any electrochemical device, RFBs are composed of cells, each consisting of two electrodes and two bipolar plates, separated by a polymeric membrane forming the two half-cells (positive and negative). Electrolytes containing the electroactive species (different in each half-cell) circulate through the electrodes of each half-cell, which exchange electrons on the surface of the felts during the charging and discharging processes.

[0007] For the device to be energetically functional, the individual cells are stacked in series to form a battery. Depending on its power, a BFR consists of a specific number of cells. A key aspect in the design of these cells is ensuring the proper circulation of the positive and negative electrolytes through the respective half-cells of each cell. To achieve this, the most common approach is to assemble the bipolar plates and membranes in flow frames that can be made of PVC, polypropylene, or other similar plastic material, where the channels through which the electrolyte flows are machined. The electrode is compressed between these frames, and to prevent leaks, various sealing techniques are used, such as flat gaskets, silicone beads, heat sealing, laser, or ultrasound, among others, which are placed between them to eliminate, or at least reduce, the common leaks that occur in this type of technology.However, current technology still lacks a simpler, more effective method than the previous ones. Therefore, an alternative method is needed to prevent leaks in BFRs in an easy and safe manner.

[0008] DESCRIPTION OF THE INVENTION

[0009] The present invention describes a redox flow battery formed by at least one cell or a stack of cells that incorporate flow distributors with integrated channels that house the electrodes, and the rest of the battery components embedded in a resin block that is distributed around the battery components, sealing it, and the manufacturing method of this battery is described.

[0010] Flow distributors can be manufactured by 3D printing, machining, molding, or other suitable method and incorporate channels through which the electrolyte flows to the electrode of each half cell, which is housed in the center of each flow distributor.

[0011] The integrated flow distributor comprises a frame and two conduits that, when joined with other conduits in other flow distributors, form the distribution conduits through which the electrolyte enters and exits the battery and is distributed to each half-cell. The frame includes a central opening that houses the electrode.

[0012] The hollow conduits extend from the top and bottom sides of the frame, respectively, and are connected to the central opening, which houses channels that distribute the electrolyte to the electrodes. Their dimensions (flow cross-section) are adjusted to the required electrolyte flow rate according to a maximum flow factor. The design of these elements also allows for the precise insertion of the electrodes through which the positive or negative electrolytes circulate, depending on the half-cell.

[0013] Once an electrode is added to the flow distributor with integrated channels, a half-cell is formed by placing a polymeric membrane on one side of the electrode and a bipolar plate on the other. To complete a cell, another flow distributor (with opposite flow direction) must be mounted with the electrode on the polymeric membrane and another bipolar plate placed on its free side. Depending on the power required from a battery, the required current will define the area of ​​the electrodes and, therefore, the size of the flow distributors with integrated channels. The voltage will be determined by the number of cells. As is common in these electrochemical devices, the last two bipolar plates (ends) will be in contact with current collector plates that constitute the battery terminals, which can be made of brass, steel, copper, or another electrically conductive material.

[0014] The present invention also relates to a method of manufacturing the battery which proposes the consecutive assembly of the cells as described in the previous paragraph and then the subsequent sealing by filling the four sides of the battery with a resin, such that all the external edges of the battery elements, for example, flow distributors, polymeric membranes, bipolar plates and collector plates, are completely covered.

[0015] The terminal plates are designed to have slots or recesses that allow the placement of sheets of Teflon, methacrylate, or other material, forming a formwork around the battery that allows the resin to be confined around all the components. This creates a volume into which the resin is introduced. Once solidified, it forms a block adapted to the irregularities of each of the battery components. Thus, the resin covers all gaps and slots except the flow conduits, preventing both electrolyte leakage to the outside and electrolyte crossing between the cells through external paths, achieving simple and effective sealing of the battery. Furthermore, this system eliminates the need to use internal elements such as flat gaskets, gaskets, silicone cords, etc. to ensure a seal.

[0016] Thus, the resin will surround the bipolar plates, the polymer membranes, the flow distributors, and the two current collector plates, sealing the assembly without allowing electrolyte leakage, regardless of the level of precision of the different components, for example, their thickness and dimensions.

[0017] DESCRIPTION OF THE DRAWINGS

[0018] To complement the description being made and in order to help better understand the characteristics of the invention, in accordance with a preferred example of practical embodiment thereof, a set of drawings is attached as an integral part of said description in which, for illustrative and non-limiting purposes, the following has been represented: Figure 1 - Shows a perspective view of the flow distributor with integrated channels with the inserted electrode (a) and of the flow distributor in which the circulation of the electrolyte can be observed (b)

[0019] Figure 2 - Shows a perspective view of a redox flow battery half-cell.

[0020] Figure 3 - Shows a perspective view of a redox flow battery cell.

[0021] Figure 4 - Shows a perspective view of the redox flow battery consisting of three uncompressed cells.

[0022] Figure 5 - Shows a perspective view of the redox flow battery consisting of three compressed cells.

[0023] Figure 6 - Shows a perspective view of the redox flow battery encapsulated with the resin.

[0024] Figure 7 - Shows another perspective view of the three-cell redox flow battery encapsulated with the resin.

[0025] Figure 8 - Shows a graph representing a constant current charge and discharge cycle of the redox flow battery.

[0026] PREFERRED EMBODIMENT OF THE INVENTION

[0027] In view of the figures, a preferred embodiment of the redox flow battery object of the present invention is described below, which comprises one or several cells arranged consecutively, in which each cell comprises the following elements in contact with each other and placed one after the other: a bipolar plate (4), an electrode (3), a polymeric membrane (5), another electrode (3) and another bipolar plate (4) as shown in Figures 2 and 3. Each cell additionally comprises a flow distributor (1) for each electrode comprising a frame that incorporates a central opening that constitutes the housing that houses the electrode and internal channels through which the electrolyte that is distributed towards the electrode circulates.As can be seen from Figure 1 , the flow distributor (1 ) comprises two conduits (2) through which the electrolytes circulate perpendicular to the frame, which extend respectively from the upper side and from the lower side of the frame and which are connected to the central opening by means of internal channels, in which the conduits (2) of one flow distributor (1 ) are located at opposite ends to the conduits (2) of the other adjacent flow distributor (1 ). Said battery also comprises a resin block located between the terminal plates (6) that encapsulates the entire perimeter of the cell / ies in which the described elements that make up the cell have been previously compressed.

[0028] As can be seen in Figure 6, the end plates (6) may comprise lateral, upper and lower grooves (9) intended to facilitate the temporary fitting of sheets (8) that form a receptacle like formwork intended to receive the resin (10). In any case, the sheets (8) may also be glued to the end plates (6) without the need for grooves (9). The resin (10) used may be epoxy resin or another type of resin. The sheets (8) may be made of a non-adherent material, for example, Teflon.

[0029] On the lower terminal plate (6), which may be blind or not depending on whether the electrolyte flow in each circuit is in a “U” shape (input and output connectors on the same terminal plate) or in a “Z” shape (input and output connectors on different terminal plates (6)), the current collector plate (7) is arranged, which incorporates one of the terminals (12) for the electrical connection of the battery.

[0030] In another embodiment of the present invention, a method for manufacturing a redox flow battery formed by one or more consecutively arranged cells, each cell comprising two bipolar plates (4), a polymeric membrane (5) and two electrodes (3), comprises the steps of: placing an end plate (6) and then placing a current collector plate (7) on the end plate (6); forming a cell by placing in this order a bipolar plate (4) on top of the current collector plate (7), a first flow distributor (1) with two integrated conduits (2) and inserting an electrode (3) into said flow distributor (1). Next, a polymeric membrane (5), another flow distributor (1) with another electrode (3) inserted, where the orientation of the conduits (2) of the first flow distributor (1) is opposite to that of the second flow distributor.If the battery is made up of more cells, another bipolar plate (4) is added, another flow distributor (1) with the electrode (3) inserted, another membrane (5) and, finally, the corresponding flow distributor (1) with the electrode (3) inserted. Finally, the battery is closed by adding another terminal plate (6) with another current collector plate (7) and compressing all the elements added in the previous steps using a fixing device or a press system; sheets (8) are added between the terminal plates (6), defining a receptacle that encompasses the entire perimeter of the battery, the receptacle is filled with a resin (10).

[0031] The resin (10) is deposited until it reaches a level at the top that leaves the final ends of the terminals (12) of the current collector plates (7) free. In this way, the resin (10) fills the entire periphery of the battery giving the appropriate consistency and tightness and preventing the electrolyte from touching and damaging the metal of the current collector plate (7). Then the curing time indicated by the manufacturer of the resin (10) is awaited to ensure that it solidifies completely, which, for the one used in the test, can be between 12 and 24 hours. From that moment on, the sheets (8) can be removed, or not, from the formwork.

[0032] Example 1.

[0033] To validate a redox flow battery manufactured according to the method of the present invention, a charge and discharge test is performed, showing optimal performance at all times and without any type of leaks in the redox flow battery.

[0034] The test uses a 5-cell redox flow battery, with a total volume of 60 cm2 (including resin). The graph in Figure 8 shows the results of the test, which lasted 2 hours and 40 minutes. It corresponds to a charge cycle at a constant current intensity of 3 A (current density of 50 mA / cm2) until the battery reaches a voltage of 8.25 V (1.65 V / cell), from which it proceeds to discharge demanding a constant current intensity of 3 A. The average charging power supplied is 21 W (350 mW / cm2), with a maximum value of 24.6 W, while in discharge the average power obtained is 14.1 W (235 mW / cm2) reaching a maximum of 21 W. The energy efficiency is 67%, understood as the quotient between the energy produced in the discharge process and the energy consumed during charging.

Claims

CLAIMS 1. Redox flow battery comprising two terminal plates (6) at both ends, in contact with the corresponding current collector plates (7) and one or more cells arranged consecutively, wherein each cell comprises the following elements in contact with each other and placed one after the other: a bipolar plate (4), an electrode (3), a polymeric membrane (5), another electrode (3) and another bipolar plate (4), where: the cell additionally comprises a flow distributor (1) for each electrode, where the flow distributor (1) in turn comprises: a frame that incorporates a central opening that constitutes the housing that houses the electrode and internal channels (11), through which the electrolytes that are distributed towards the electrode circulate, and two conduits (2) through which the electrolyte circulates perpendicular to the frame,which extend respectively from the upper side and from the lower side of the frame and which are connected to the central opening by means of internal channels (11), in which the ducts (2) of a flow distributor (1) are located at opposite ends to the ducts (2) of an adjacent flow distributor (1), the bipolar plates (4) and the polymeric membranes (5) are free peripherally, the battery being characterized in that: it comprises a resin block located between the terminal plates (6) that encapsulates the entire perimeter of each cell in which the described elements that make up the cell have been previously compressed., 2. The battery of claim 1, wherein, in the case of incorporating two or more cells, the conduits (2) of a flow distributor (1) are connected to the conduits (2) of another flow distributor (1) located after the adjacent flow distributor (1).

3. The battery of claim 1, wherein the terminal plates (6) comprise lateral, upper and lower slots (9) intended to facilitate the temporary fitting of sheets (8) that form a formwork-like receptacle intended to limit the volume of the resin (10).

4. Method for manufacturing a redox flow battery comprising one or several cells arranged consecutively, in which each cell comprises two bipolar plates (4), one polymeric membrane (5) and two electrodes (3), characterized in that it comprises the stages of: - place an end plate (6), - place a current collector plate (7) on the terminal plate (6), - forming a cell by placing, in this order, a bipolar plate (4) on top of the current collector plate (7), a first flow distributor (1) with two conduits (2) and with an electrode (3) inserted in the flow distributor (1), a polymer membrane (5), another flow distributor (1) with another electrode (3) inserted, where the orientation of the conduits (2) of the flow distributor (1) is opposite to that of the other flow distributor, - if the battery is made up of more cells, continue by placing another bipolar plate (4), another flow distributor (1) with the electrode (3) inserted, another membrane (5) and, finally, the corresponding flow distributor (1) with the electrode (3) inserted, and continue in the same order until reaching the desired number of cells, - close the battery by placing another terminal plate (6) with another current collector plate (7) and compressing all the elements placed in the previous steps by means of a fixing element or a device or a press system, - place sheets (8) between the terminal plates (6), defining a receptacle that encompasses the entire perimeter of the battery, - fill the receptacle with a resin (10), - wait for the resin curing time (10) and remove or leave the sheets (8).

5. The method of claim 4, wherein the sheets (8) comprise side sheets (8) and a lower sheet (8) leaving the upper face free where the terminals (12) of the current collector plates (7) are located.

6. The method of claim 4, wherein the sheets (8) comprise side sheets (8), a bottom sheet (8) and an upper sheet (8) provided with a filling hole.

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