DE102020128060A1 - Redox flow cell and process for its manufacture - Google Patents

Abstract

A redox flow cell (1) is produced by 3D printing a plastic frame (2), electrodes (3, 4) and a membrane (5). In addition, metallic conductors (6, 7), which are connected to the electrodes (3, 4) and run through the plastic frame (2), are produced in 3D printing. The electrodes (3, 4) have a toothed structure when viewed in cross section.

Description

The invention relates to a method for producing a redox flow cell which has a plastic frame as a flow frame, electrodes and a membrane separating two half cells from one another being arranged in the flow frame. The invention also relates to a redox flow cell which comprises components designed as 3D printed parts.

Redox flow cells are the building blocks of redox flow batteries, which are also known as redox flow batteries. Energy-storing electrolytes circulate in two separate circuits in a redox flow battery. The plastic frames mentioned form sections of these circuits. An ion exchange takes place through the membrane, which is arranged in the plastic frame.

A generic method for producing a redox flow cell is from the DE 10 2016 007 973 A1 known. Various polymers are used in the known manufacturing process. In this case, an electrically conductive polymer, from which an electrode is produced, is materially bonded to another polymer, from which the flow frame is built, by means of a fusion bond. In addition to the electrodes and the flow frame, the membrane of the well-known redox flow cell can also be produced with the help of 3D printers. Current conductors, which can be in the form of plates or rod-shaped conductors, are provided as electrical connection elements of the known redox flow cell. Production of the current arrester is carried out in the DE 10 2016 007 973 A1 not received.

Further designs of redox flow batteries are for example in the documents EP 3 534 448 A1 and WO 2019/046724 A1 described. In the latter case, the redox flow battery is made up of plate-shaped components.

The invention is based on the object of further developing a redox flow cell compared to the prior art mentioned, in particular under manufacturing aspects, whereby a particularly high process reliability should also be provided under the conditions of series production.

This object is achieved according to the invention by a method for producing a redox flow cell according to claim 1. The object is also achieved by a redox flow cell with the features of claim 8. In the following in connection with the device, that is to say the Redox flow cell, explained configurations and advantages of the invention also apply mutatis mutandis to the manufacturing process and vice versa.

The redox flow cell is produced in that both a plastic frame, which acts as a flow frame, as well as electrodes, a membrane and metallic conductors, which are used for the electrical connection of the redox flow cell, are produced in a 3D printing process. As part of the manufacturing process, a switch is made between the additive manufacturing of non-metallic components, that is to say at least the plastic frame and the membrane, and the likewise additive manufacturing of metallic components. The two electrodes are preferably also made from a non-metallic material, namely an electrically conductive polymer.

Overall, material connections between metallic and non-metallic components are thus produced in a rational, reliable manner. At the same time, the tightness of the redox flow cell, that is to say the tight enclosure of the electrolytes in the sections of the respective fluid circuits formed by the flow frame, is ensured in a simple manner.

The connections of the electrical conductors, which are provided as connecting lines of the redox flow cell, with the electrodes, which are preferably made of polymer materials, represent electrically conductive, material connections.

At the same time, the metallic conductors are firmly bonded to the plastic frame, with no electrically conductive contacts being formed at the corresponding points due to the electrically insulating properties of the plastic frame. In a corresponding manner, the connection of the membrane to the plastic frame is made cohesive and liquid-tight without representing an electrical connection. In a manner known per se, the membrane is a semipermeable component, in particular a component that is permeable to protons.

For the electrical connection of the metallic conductors to the electrodes, which are also electrically conductive but made of a different material, each metallic conductor in a preferred embodiment has a connection section that is directly connected to the associated electrode and is wider than the rest of the conductor. The metallic conductors are designed, for example, as printed conductor tracks. In principle, the metallic conductors produced in 3D printing can have any cross-section, including a circular cross-section.

In all cases, the metallic conductors that connect an electrical Allow consumers to the redox flow cell, in a preferred embodiment, not non-destructively removable from the plastic frame in which they are embedded. In particular in the longitudinal direction of the conductors, these are embedded in a liquid-tight manner in the plastic frame, the tightness being provided without additional components, such as sealing rings.

According to one possible configuration, the electrodes of the redox flow cell have a toothed structure in cross section. The teeth present here provide for a regular or irregular shape of the electrodes with teeth, prongs or prongs. A tooth, prong or prong is considered here to be any raised geometric structure which, viewed macroscopically, protrudes beyond the plane of the membrane. This provides a large electrode surface, with the electrolyte remaining free to flow through the redox flow cell. The thickness, that is to say the minimum thickness, of each electrode is in particular less than half the tooth height and is preferably in the range from 0.2 to 2 mm. The height of the teeth measured orthogonally to the membrane (= measured from the electrode surface to the maximum height of a tooth arranged on the respective electrode surface) is in particular in the range from 1.5 to 3 mm. A tooth gap is formed between two teeth of the set of teeth, which gap is delimited on one side between the teeth by the electrode surface, a width of the tooth gap preferably being more than the height of each half-cell.

Regardless of the cross-sectional design of the electrodes and the entire redox flow cell, a redox flow battery can be built up by them, which is also generally referred to as a bipolar stack.

• In einer ersten Fertigungsphase wird Kunststoffmaterial durch 3D-Druck verarbeitet, wobei ein unvollständiger Aufbau des Kunststoffrahmens und/oder der Elektroden erfolgt.

The additive manufacturing of the redox flow cell comprises, in an advantageous process management, three different manufacturing phases:

• In a first production phase, plastic material is processed by 3D printing, with an incomplete construction of the plastic frame and / or the electrodes.

In a second production phase, the conductors are generated additively from a metallic material, forming integral connections on the plastic material that was partially built up in the previous phase.

Finally, in a third production phase, plastic material is processed again by 3D printing, with material connections being made both to the plastic material that has already been built up and to the metallic conductors.

The membrane can be manufactured, for example, within the first manufacturing phase or within the third manufacturing phase or in a separate phase. The workpiece, i.e. the redox flow cell that is being set up using 3D printing, can remain in an unchanged position in a production system during all production phases.

• 1 ein Ausführungsbeispiel einer Redox-Flow-Zelle in einer vereinfachten Schnittdarstellung,
• 2 ein nicht beanspruchtes Vergleichsbeispiel in einer Darstellung analog 1.

An exemplary embodiment of the invention and a comparative example are explained in more detail below with reference to a drawing. Show here:

• 1 an embodiment of a redox flow cell in a simplified sectional view,
• 2 a comparative example not claimed in an analog representation 1 .

The reference symbols used in the two figures are the same as long as the parts concerned are shaped identically or have a comparable function.

A designed according to the invention, in 1 The redox flow cell sketched and designated as a whole by 1 has a plastic frame 2 as a flow frame, two electrodes 3 , 4th , a membrane 5 as well as metallic conductors 6th , 7th on. One to the ladder 6th , 7th connected consumer 8th is not part of the redox flow cell 1 .

Only in the comparative example according to 2 is the plastic frame 2 from individual frame parts 9 , 10 , 11 composed. How out 2 As can be clearly seen, this results in numerous contact points between the electrodes that have to be sealed against one another 3 , 4th and the plastic frame 2 as well as between the membrane 5 and the plastic frame 2 . In addition - in 2 not shown - the problem of sealing also exists between electrical connection components and other components.

• Die Höhe der Redox-Flow-Zelle 1 ist mit H bezeichnet. St bezeichnet die quer zur Höhe H zu messende Stegbreite des Kunststoffrahmens 2. In dem Kunststoffrahmen 2 sind durch die Membran 5 zwei Halbzellen 12, 13 voneinander getrennt. Die Höhe einer Halbzelle 12, 13 ist mit H₁₂ bzw. H₁₃ bezeichnet. In die Halbzellen 12, 13 ragen Zähne 14, 15 der Elektroden 3, 4. Die orthogonal zur Membran 5 gemessene Höhe der Zähne 14, 15 ist mit H_Z bezeichnet. Zwischen zwei Zähnen 14 ist eine Zahnlücke 16 mit einer Breite Bz gebildet. Die Zahnlücke 16 begrenzt eine weitere, nicht dargestellte Halbzelle. Die Breite Bz der Zahnlücke 16 beträgt mehr als die Höhe H₁₂ , H₁₃ einer jeden Halbzelle 12, 13. Die Stärke, das heißt minimale Dicke, einer jeden Elektrode 3, 4 ist mit S_E bezeichnet und beträgt weniger als die Hälfte der Zahnhöhe Hz.

Also for different dimensions of the redox flow cell 1 are in the comparative example according to 2 and in the exemplary embodiment according to 1 the same designations are used:

• The height of the redox flow cell 1 is with H designated. St denotes the transverse to the height H web width to be measured of the plastic frame 2 . In the plastic frame 2 are through the membrane 5 two half-cells 12th , 13th separated from each other. The height of a half cell 12th , 13th is with H ₁₂ or. H ₁₃ designated. In the half-cells 12th , 13th protrude teeth 14th , 15th of the electrodes 3 , 4th . The orthogonal to the membrane 5 measured height of the teeth 14th , 15th is with H _Z designated. Between two teeth 14th is a tooth gap 16 formed with a width Bz. The tooth gap 16 limited one further, not shown half-cell. The width Bz of the tooth gap 16 is more than the height H ₁₂ , H ₁₃ of each half-cell 12th , 13th . The strength, i.e. minimum thickness, of each electrode 3 , 4th is with S _E and is less than half the tooth height Hz.

In the embodiment according to 1 are both the non-metallic components, i.e. the plastic frame 2 who have favourited electrodes 3 , 4th , and the membrane 5 , as well as the metallic conductors 6th , 7th produced using the 3D printing process, i.e. through additive manufacturing. This also applies to connection sections 17th , which the metallic ladders 6th , 7th are attributable and completely within the plastic frame 2 lie. Compared to the rest of the leader 6th , 7th widened connection sections 17th close directly to the electrodes 3 , 4th at, being different from those in the half-cells 12th , 13th located electrolytes are spaced.

Within the entire process of manufacturing the redox flow cell 1 to 1 represents the additive manufacturing of the ladder 6th , 7th including the connection sections 17th represents an intermediate step, the steps for additive manufacturing of the non-metallic components 2 , 3 , 4th , 5 are upstream and downstream.

List of reference symbols

1

Redox flow cell

2

Plastic frame

3

electrode

4th

electrode

5

membrane

6th

ladder

7th

ladder

8th

consumer

9

Frame part

10

Frame part

11

Frame part

12th

Half cell

13th

Half cell

14th

tooth

15th

tooth

16

Tooth gap

17th

Connection section

BZ

Width of the tooth gap

H

Redox flow cell height

H12

Half cell height 12

H13

Half cell height 13th

HZ

Height of the tooth

SE

Strength of an electrode

St.

Web width

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was 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.

Patent literature cited

• DE 102016007973 A1 [0003]
• EP 3534448 A1 [0004]
• WO 2019/046724 A1 [0004]

Claims (10)

Method for producing a redox flow cell (1), a plastic frame (2), electrodes (3, 4) and at least one membrane (5) being produced in 3D printing, with additional metallic conductors (6, 7) , which are connected to the electrodes (3, 4) and pull through the plastic frame (2), are generated in 3D printing, and the electrodes (3, 4) are each designed to have a toothed structure when viewed in cross section. Procedure according to Claim 1 wherein each electrode (3, 4) is formed to have a plurality of teeth (14, 15) at least on its surface facing a membrane (5). Procedure according to Claim 1 or 2 , whereby liquid-tight connections of the electrodes (3, 4) and the membrane (5) to the plastic frame (2) are produced by the 3D printing. Procedure according to Claim 3 , wherein the metallic conductor (6, 7) has a connection section (17) directly adjoining the electrode (3, 4) and widened in comparison to the rest of the conductor (6, 7). Method according to claim one of the Claims 1 to 4th wherein the conductors (6, 7) are embedded in the plastic frame (2) so that they cannot be removed without being destroyed. Method according to claim one of the Claims 1 to 5 , wherein the electrodes (3, 4) are made from a conductive polymer by 3D printing. Method according to claim one of the Claims 1 to 6th , wherein in a first manufacturing phase plastic material is processed by 3D printing, in a second manufacturing phase the conductors (6, 7) are additively built up from a metallic material to form material connections on the plastic material that has already been partially built up in the previous phase, and in a In the third manufacturing phase, plastic material is again processed by 3D printing, with material connections being made both to the plastic material that has already been built up and to the metallic conductors (6, 7). Procedure according to Claim 7 , whereby the workpiece, i.e. the redox flow cell (1) under construction by 3D printing, is held in an unchanged position during the three manufacturing phases. Redox flow cell (1) with components made of polymer materials, namely a plastic frame (2), electrodes (3, 4) and at least one membrane (5), and with metallic components, namely on the electrodes (3, 4 ) connected conductors (6, 7), whereby both the metallic components (6, 7) and non-metallic components (2, 3, 4, 5) are designed as 3D-printed components and the conductors (6, 7) cohesively with the plastic frame (2) and the electrodes (3, 4) are connected, and the electrodes (3, 4) each describing a toothed structure when viewed in cross section. Redox flow cell (1) Claim 9 wherein each electrode (3, 4) has regular or irregular teeth at least on its surface facing a membrane (5).

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