Method for producing an electrochemical cell by means of additive manufacturing

Abstract

The invention relates to a method for producing an electrochemical cell (1), in particular for binding carbon dioxide (CO2), comprising a first electrode (2) and a second electrode (3), which are separated by a membrane (4). According to the invention, during the production of the first electrode (2) and / or the second electrode (3), at least one layer of an electrode material is applied to the membrane (4) in an additive manufacturing process, and at least one cavity (5, 6) is formed during the application of the electrode material.

Description

[0001] R.414077

[0002] - 1 -

[0003] Description

[0004] title

[0005] Method for manufacturing an electrochemical cell

[0006] The present invention relates to a method for producing an electrochemical cell with the features of the preamble of claim 1. The electrochemical cell can in particular be a cell for binding carbon dioxide (CO2).

[0007] The preferred application area of ​​the invention is electrochemical systems or plants for carbon dioxide separation.

[0008] State of the art

[0009] Electrochemical cells used for carbon dioxide capture consist of at least two electrodes that are electrically connected and separated by a separator or membrane. At a cathode-side electrode, a gas, such as carbon dioxide, is bound from a gas or gas mixture through chemical processes. An anode-side electrode, on the other hand, acts as an electron donor and provides the electrons necessary for the capture reaction. The separator or membrane is permeable to ions, which ensure charge balance in the electrochemical cell. Gas capture can be achieved in a single process step by changing the temperature and / or pressure. In this process, the carbon dioxide is dissolved in a liquid, particularly an aqueous electrolyte or an ionic liquid, by a partial pressure gradient from gas to liquid.Gas separation can also be carried out in two process steps. In this case, the first process step is identical to the process described above. In a second process step, R.414077.

[0010] - 2 - a chemical reaction then takes place with the liquid. Alternatively or additionally, an electrical voltage can be applied to the electrode so that dissolved and / or chemically reacted carbon dioxide, which has reached the liquid-electrode interface from the gas-liquid interface by diffusion processes – possibly supported by active and / or passive convection processes – is bound to the surface of the electrode, at least temporarily, by charge displacement or charge transfer. The process is reversible, i.e., a change in temperature or pressure back to the initial state or removal of the voltage leads to a controlled release of the previously bound gas.

[0011] Electrodes for such electrochemical cells typically have a core of electrically conductive substrate material, which is completely coated with a functional material or material mixture. The functional material or mixture determines the functionality of the respective electrode, i.e., whether it serves to provide electrons or to bind a gas. The substrate material essentially only provides support. Examples of commonly used substrate materials include carbon fiber fleeces, carbon nanotubes (CNTs), carbon fiber mats, or mesoporous carbons. The functional material or mixture is typically polymers in the form of a polymer suspension, which, in addition to the polymer, usually contains at least one additive and a solvent. The polymer suspension is typically applied using an immersion process.

[0012] Based on the aforementioned prior art, the present invention aims to increase the efficiency of an electrochemical cell, in particular an electrochemical cell for binding carbon dioxide. Furthermore, the electrochemical cell should be as simple and cost-effective to manufacture as possible.

[0013] To solve the problem, the method for manufacturing the electrochemical cell with the features of claim 1 is proposed. Advantageous embodiments of the invention are described in the dependent claims.

[0014] Disclosure of invention R.414077

[0015] - 3 -

[0016] A method for manufacturing an electrochemical cell, particularly for binding carbon dioxide (CO2), is proposed, comprising a first electrode and a second electrode separated by a membrane. According to the invention, in the manufacture of the first electrode and / or the second electrode, an electrode material is applied to the membrane in at least one layer using an additive manufacturing process, and at least one cavity is created during the application of the electrode material.

[0017] By using an additive manufacturing process, an electrode for an electrochemical cell can be produced in a single process step. This reduces the complexity of the manufacturing process and thus the costs compared to conventional manufacturing methods. Furthermore, the additive manufacturing process allows for the simple integration of at least one cavity. This cavity can extend from a surface into the electrode material or be formed as a hollow space within the electrode. In particular, a cavity located on the surface enables further functionalization, which increases the efficiency of the electrode. In the case of an electrode for binding a gas, the at least one cavity can shorten the diffusion path.

[0018] The additive manufacturing process can, in particular, be a laser printing process.

[0019] Preferably, when applying the electrode material to the membrane, the membrane itself is used as the support material. This eliminates the need for a separate support material, particularly one located in the core. Integrating the support material function into the membrane reduces costs, as two functions are realized by a single component. Furthermore, eliminating a core support material in the electrode increases the usable cross-section available for gas phase binding, i.e., the functional density of the electrode. Increased functional density, in turn, leads to a significantly improved efficiency of the electrochemical process.

[0020] - 4 -

[0021] Cell. According to a preferred embodiment of the invention, it is therefore proposed that when applying the electrode material to the membrane, the membrane is used as the sole support material.

[0022] Furthermore, preferably, after the electrode material has been applied to the membrane, it is subjected to a thermal treatment. This thermal treatment promotes the hardening of the electrode material and increases the mechanical stability of the electrode.

[0023] In a further development of the invention, it is proposed that the use of a solvent-containing electrode material be omitted in the production of the first electrode and / or the second electrode. Solvents pose a safety risk to humans due to their flammability and toxicity. By deliberately avoiding solvents, the safety of the process can be increased. Furthermore, costs can be saved, as no safety measures, such as the installation of a fume hood and / or solvent detector, are required.

[0024] Preferably, at least one electrode material made of a gas-absorbing polymer, preferably a polymer from the quinone group, is used in the production of the first electrode. Gas-absorbing polymers, especially quinones, have a particularly high affinity for carbon dioxide and are able to bind large quantities of carbon dioxide.

[0025] Furthermore, it is preferable that at least one electrode material made of an electron-releasing polymer, preferably a polymer from the ferrocene group, is used in the production of the second electrode. The electrode material of the second electrode facilitates the release of electrons to the first electrode, with a polymer from the ferrocene group being particularly advantageous in this respect. Releasing larger quantities of electrons increases the efficiency of the electrochemical cell.

[0026] Advantageously, during the fabrication of the first electrode and / or the second electrode, the electrode material is applied to the membrane in several steps. This stepwise application allows for thinner layers, as described in R.414077.

[0027] - 5 - that a higher dimensional accuracy of the layer can be achieved. This is particularly advantageous if at least one cavity is to be formed in the layer. Furthermore, before the application of another layer, the electrode material can be at least partially cured or hardened, so that the dimensional accuracy is further increased, as uniform curing of the individual layers can be ensured. Curing can occur passively and / or actively, or be controlled. Passive curing can occur through interaction of the electrode material with the environment, especially with oxygen and / or light. To actively promote curing, the layer-by-layer applied electrode material can be subjected to thermal treatment, for example, using a laser.

[0028] Therefore, it is preferred that the applied electrode material is subjected to thermal treatment after each step or after several steps in the production of the first electrode and / or the second electrode. Whether thermal treatment after each step or only after several steps is advantageous depends in particular on the applied layer thicknesses of the electrode material.

[0029] In a further development of the invention, it is proposed that, during the manufacture of the first electrode and / or the second electrode, at least one cavity is formed in the form of a point depression and / or a linear groove. The shape of the at least one cavity influences its function. If the at least one cavity is formed as a linear groove, it can function as a flow channel and accelerate the supply and removal of the gas or gas mixture. This increases the efficiency of the electrochemical cell. A cavity formed as a point depression can, in particular, serve to store an ionic liquid, which supports the charge exchange of the membrane and thus also improves the efficiency of the system.

[0030] Preferably, in the production of the first electrode and / or the second electrode, the electrode material is applied in a total layer thickness of 50 pm to 5000 pm, preferably 100 pm to 500 pm. An increase in the total layer thickness increases the amount of polymer available for bonding. R.414077

[0031] - 6 - the gas phase is available. Higher total layer thicknesses thus lead to a higher storage capacity of the electrochemical cell.

[0032] Furthermore, preferably, in the manufacture of the first electrode and / or the second electrode, at least one cavity with a depth of 10 pm to 2000 pm, preferably 50 pm to 300 pm, is formed in the electrode material. The greater the depth of the at least one cavity, the more gas or gas mixture can be transported, or the more ionic liquid can be absorbed.

[0033] Further measures improving the invention are described in more detail below with reference to the figures, which represent preferred embodiments. The figures show:

[0034] Fig. 1 shows a schematic cross-section through two stacked electrochemical cells produced according to a first preferred embodiment of a method according to the invention, and

[0035] Fig. 2 shows a schematic top view of an electrochemical cell that has been produced according to a second preferred embodiment of a method according to the invention.

[0036] Detailed description of the drawings

[0037] Figure 1 shows several electrochemical cells 1 in a stacked arrangement. Each cell 1 has a first electrode 2, a second electrode 3, and an intermediate membrane 4. According to the invention, the electrodes 2 and 3 were manufactured on the membrane 4 using an additive manufacturing process. During operation of the cells 1, the first electrode 2 is in contact with a gas or gas mixture via a surface. This gas or gas mixture is supplied and discharged via gas channels 9 that run perpendicular to the plane of the cells 1. The first electrode 2 has at least one cavity 5 in the form of a linear groove, which serves as a flow channel for the gas or gas mixture. The second electrode 3 also has at least one cavity 6 in the form of a point depression. An ionic liquid can be stored in this cavity, as described in R.414077.

[0038] - 7 - which supports the charge exchange of the membrane 4 required for the electrochemical reaction in cell 1. The individual electrochemical cells 1 are separated from each other by bipolar plates 8, which are electrically conductive. Frame parts 7 are arranged between the bipolar plates 8, which serve to stabilize and reinforce the respective cell 1.

[0039] The second electrode 3 acts as an electron donor, providing electrons for the reactions at the first electrode 2 by converting ions. These electrons flow across the adjacent bipolar plates 8 to the first electrode 2, where they are converted into one of the gases from the gas phase. The ion transport across the membrane 4 and the transport of electrons across the bipolar plates 8 thus ensure charge balance in the electrochemical cell 1.

[0040] In the production of the first electrode 2, at least one electrode material made of a gas-absorbing polymer, preferably a polymer from the quinone group, is used. The electrode material is applied to the membrane 4, which serves as the support material, preferably as the sole support material, by an additive manufacturing process. The electrode material is applied by forming the described cavities 5. After application, the electrode material is preferably subjected to a thermal treatment to accelerate curing.

[0041] The production of the second electrode 3 proceeds analogously. However, instead of a gas-absorbing polymer, an electron-releasing polymer, preferably a polymer from the ferrocene group, is used as the electrode material. Furthermore, instead of groove-shaped cavities 5, cavities 6 in the form of point depressions are formed.

[0042] Figure 2 shows a top view of an electrochemical cell 1 with a first electrode 2 produced according to a method according to the invention, that is, the first electrode 2 has been produced in an additive manufacturing process on a membrane 4, which thereby acts as a support material. The additive manufacturing process facilitates the formation of cavities 5. This R.414077

[0043] - 8 -

[0044] Cavities 5 are arranged essentially linearly and form a continuous network of flow channels in the electrode 2. These flow channels accelerate the transport of a gas or gas mixture to and from the cell 1 via gas channels 9.

Claims

R.414077 - 9 - Claims 1. Method for producing an electrochemical cell (1), in particular for binding carbon dioxide (CO2), comprising a first electrode (2) and a second electrode (3) separated by a membrane (4), characterized in that, in the production of the first electrode (2) and / or the second electrode (3), an electrode material is applied to the membrane (4) in at least one layer using an additive manufacturing process and at least one cavity (5, 6) is formed during the application of the electrode material.

2. Method according to claim 1, characterized in that when applying the electrode material to the membrane, the membrane (4) is used as a carrier material, preferably as the only carrier material.

3. Method according to claim 1 or 2, characterized in that after the electrode material is applied to the membrane (4) the electrode material is subjected to a thermal treatment.

4. Method according to one of the preceding claims, characterized in that the use of a solvent-containing electrode material is dispensed with in the manufacture of the first electrode (2) and / or the second electrode (3).

5. Method according to one of the preceding claims, characterized in that in the manufacture of the first electrode (2) at least one electrode material made of a gas-absorbing polymer, preferably a polymer from the group of quinones, is used. R.414077 - 10 - 6. Method according to one of the preceding claims, characterized in that in the manufacture of the second electrode (3) at least one electrode material made of an electron-releasing polymer, preferably a polymer from the group of ferrocenes, is used.

7. Method according to one of the preceding claims, characterized in that in the manufacture of the first electrode (2) and / or the second electrode (3) the electrode material is applied to the membrane (4) in several steps, wherein preferably after each step or after several steps the applied electrode material is subjected to a thermal treatment.

8. Method according to one of the preceding claims, characterized in that in the manufacture of the first electrode (2) and / or the second electrode (3) at least one cavity (5.6) is formed in the form of a point depression and / or a linearly extending groove.

9. Method according to one of the preceding claims, characterized in that in the manufacture of the first electrode (2) and / or the second electrode (3) the electrode material is applied in a total layer thickness of 50 pm to 5000 pm, preferably 100 pm to 500 pm.

10. Method according to one of the preceding claims, characterized in that in the manufacture of the first electrode (2) and / or the second electrode (3) at least one cavity (5, 6) with a depth of 10 pm to 2000 pm, preferably 50 pm to 300 pm, is formed in the electrode material.

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