Electrochemical cell for carbon dioxide conversion and cell stack comprising such cell

Abstract

The present invention provides an electrochemical cell for carbon dioxide conversion characterized by an electrode-solid electrolyte assembly having a solid electrolyte layer made of a cation-exchanged solid electrolyte. A negative electrode and a positive electrode are integrated on opposing surfaces of the electrolyte layer and each include a catalyst and a cation exchange binder. The cell comprises a porous transport layer for two electrodes and an interface layer with an anion exchange polymer between the positive electrode and its transport layer. Water is supplied to the negative electrode for oxidation, and carbon dioxide is supplied to the positive electrode for reduction to produce formic acid, ethylene, propylene, and alcohols. The cell further comprises an enhancement layer and an anti-oxidation layer in the solid electrolyte layer, and a protection structure on the edge of the enhancement layer and the anti-oxidation layer. Bipolar plates and gaskets ensure effective fluid distribution. The design has a stacked structure for a plurality of cells, supporting scalability, making it suitable for large scale applications.

Description

Technical Field

[0001] The present invention relates to an electrochemical cell, and more particularly to the field of electrochemically converting carbon dioxide into useful chemical products. The present invention relates to the design and manufacture of electrode assemblies, solid electrolytes, and related components for reducing carbon dioxide, applied to sustainable energy systems, chemical manufacturing, and environmental remediation. The present invention relates to the integration of catalysts, porous transport layers, and bipolar plates to improve the efficiency and scalability of the carbon dioxide reduction process. Background Art

[0002] The increase in greenhouse gas, i.e., carbon dioxide (CO2) emissions, has accelerated global warming, leading to climate change around the world in the past few decades. Solving this problem has become an important issue.

[0003] Consequently, recently there has been a significant increase in interest in methods for converting carbon dioxide captured from the flue gas discharged from industrial manufacturing plants or directly captured from the atmosphere into high-value-added compounds. Such methods include CO2 conversion reactions that convert carbon dioxide into other compounds through electrochemical reduction reactions, i.e., CO2 reduction reactions (CO2RR), etc.

[0004] The advantage of this method is that carbon dioxide is removed by consuming it as a reactant in an electrochemical reaction, while storing the electricity based on renewable energy such as wind energy, solar energy, and hydroelectric power in the form of high-value-added compounds, which are overproduced and discarded before use.

[0005] The carbon dioxide conversion reaction or carbon dioxide reduction reaction produces a variety of products depending on the cell structure of the conversion device, the type of electrolyte / electrode-catalyst, the characteristics of the components or materials constituting the cell, and the operating conditions. Gaseous products include carbon monoxide (CO) containing one carbon, ethylene (C2H4) and propylene (C3H6) containing multiple carbons (C 2+ ) etc. In addition, liquid products include formic acid (HCOOH) / formate containing one carbon and alcohols such as methanol (CH3OH), ethanol (C2H5OH), and propanol (C3H7OH).

[0006] The carbon dioxide reduction reaction is greatly affected by the cell structure. Conventional methods include a liquid batch cell called an "H-type cell" as Figure 1 shown.

[0007] The liquid batch cell includes an anode as the counter electrode (CE), a cathode as the working electrode (WE), and a reference electrode (RE). The anolyte of the electrolyte in the anode chamber, which is the site of the electrochemical oxidation reaction, and the catholyte of the electrolyte in the cathode chamber, which is the site of the electrochemical reduction reaction, typically both use a liquid, namely an aqueous solution. The anolyte and the catholyte are separated by a solid electrolyte located in the middle of the cell. This solid electrolyte is typically an ionomer-based, pure, or non-reinforced ion-exchange solid electrolyte (IESE).

[0008] At the anode of the liquid batch cell, a reaction (OER: oxygen evolution reaction) in which oxygen is generated occurs through water electrolysis. At the cathode, a reaction (CO2RR) in which the carbon dioxide gas dissolved in the catholyte is reduced occurs.

[0009] Due to its simple structure, the liquid batch cell can quickly and economically evaluate catalytic activity and has been widely used in catalyst analysis research. However, since the solubility of carbon dioxide in the liquid electrolyte is very low, being 34 mM at a room temperature of about 25 °C, unfortunately, the mass transfer resistance or loss is very large, and it can only operate at a very low current density, i.e., less than 100 mA / cm 2 2, thus reducing the productivity. Ultimately, the production speed of the product is greatly reduced, making large-scale production very difficult. In addition, due to the unstable cell structure and operation, the liquid electrolyte has the disadvantages of a batch cell, namely low durability and can only be used for dozens of hours.

[0010] To solve the problems of the liquid batch cell, a liquid flowcell as shown in Figure 2 has been developed.

[0011] The flow cell has the following structure: The negative electrolyte (anolyte) is located between the solid electrolyte and the negative electrode, and the positive electrolyte (catholyte) is located between the solid electrolyte and the positive electrode. The negative electrolyte and the positive electrolyte are typically liquids and are separated from each other by the solid electrolyte located in the middle of the cell. The solid electrolyte is typically an ionomer-based, pure, or non-reinforced ion-exchange solid electrolyte. In addition, the flow cell has an electrode-integrated porous transport layer (EIPTL) structure, where the negative electrode and the positive electrode are respectively attached to the negative porous transport layer (PTL) and the positive porous transport layer. In this case, different from the conventional liquid intermittent cell, carbon dioxide gas is directly supplied to the catalyst in the positive electrode through the positive porous transport layer. As a result, the rate of the carbon dioxide reduction reaction can be increased, and thus the cell current density can be increased to be greater than 100 mA / cm 2 , resulting in an increase in the product yield rate.

[0012] However, the flow cell has the following problems: Due to the presence of the negative electrolyte and the positive electrolyte, the ohmic resistance between the solid electrolyte and the electrodes increases, and flooding occurs where the pores inside the electrode-integrated porous transport layer are blocked by the liquid. The flooding of the flow cell makes it impossible to sufficiently supply the reactants required for the electrochemical reaction to the catalyst inside the electrodes, resulting in an increase in the mass transfer resistance or loss. In addition, carbon dioxide reacts with hydroxide ions (OH - ) at the positive electrode to form salts as by-products, resulting in unnecessary loss of carbon dioxide. In addition, the salts can accumulate inside the cell. As a result, disadvantageously, the reaction rate and the current density of the cell may decrease, and the performance and operability of the cell may decline.

[0013] To solve the problems of the flow cell, the following has been developed as Figure 3A solid electrolyte-based flow cell having an electrode integrated porous transport layer (EIPTL) as shown. The solid electrolyte-based flow cell with EIPTL has neither a negative electrolyte nor a positive electrolyte in its internal structure. In other words, there is no liquid electrolyte between the solid electrolyte and the electrode, and the solid electrolyte is in direct contact with the electrode, thus forming a zero-gap cell structure. As a result, the ohmic resistance of the cell is reduced and the cell performance is improved. The solid electrolyte-based flow cell with EIPTL solves many problems of conventional flow cells, but due to its adoption of the EIPTL structure, with the increase of the cell current density, there is still an overflow problem of the EIPTL caused by liquid products or water. That is, when the EIPTL is formed by directly coating an electrode paste or a catalyst paste (ink), which is a mixture of a catalyst, a catalyst carrier, a binder, and a solvent, onto the porous transport layer, the electrode paste not only penetrates to the surface of the porous transport layer but also penetrates through the pores into the interior of the porous transport layer, resulting in excessive use of the electrode paste compared to the required amount. In addition, excessive coating of the electrode paste will block the pores of the porous transport layer, thus reducing the mass transfer ability of the porous transport layer.

[0014] In addition, the EIPTL structure has a configuration in which the electrode is attached to the porous transport layer, thus making it impossible for the solid electrolyte and the electrode to be in close contact, which leads to an increase in contact resistance and a reduction in cell performance and durability.

[0015] In addition, the solid electrolyte-based flow cell with EIPTL has a configuration in which the solid electrolyte separates the negative electrode and the positive electrode from each other, and the solid electrolyte is usually an ionomer-based non-reinforced ion exchange solid electrolyte. Therefore, due to the degradation of the solid electrolyte during long-term operation, the durability of the solid electrolyte is insufficient, which may disadvantageously make the solid electrolyte thinner, resulting in an increase in the formation of pinholes. As a result, the long-term durability and stability of the solid electrolyte deteriorate. Therefore, compared with conventional liquid bulk cells and flow cells, the solid electrolyte-based flow cell with EIPTL has the beneficial effects of reducing the internal resistance of the cell and partially increasing the current density, but due to problems such as low cell performance, low long-term durability and stability, internal overflow in the cell, and difficulty in operating at high current densities, it is still not suitable for large-scale manufacturing.

[0016] The above information disclosed in this background art section is provided only to enhance the understanding of the background of the present invention. Therefore, it may include information that does not constitute the prior art known to those of ordinary skill in the art in this country. Summary of the Invention

[0017] The present invention is dedicated to solving the above problems related to the prior art.

[0018] One object of the present invention is to provide an electrochemical cell for carbon dioxide conversion suitable for large-scale production.

[0019] Another object of the present invention is to provide an electrochemical cell for carbon dioxide conversion that exhibits maximized performance due to low cell resistance.

[0020] Another object of the present invention is to provide an electrochemical cell for carbon dioxide conversion that minimizes the overflow problem.

[0021] Another object of the present invention is to provide an electrochemical cell for carbon dioxide conversion having a high operating current density.

[0022] Another object of the present invention is to provide an electrochemical cell for carbon dioxide conversion that is highly durable, thus having a long lifespan and high stability.

[0023] The objects of the present invention are not limited to the above objects. The objects of the present invention will be clearly understood from the following description and can be achieved by the means defined in the claims and their combinations.

[0024] In one aspect, the present invention provides an electrochemical cell for carbon dioxide conversion, which includes an electrode-solid electrolyte assembly. The electrode-solid electrolyte assembly includes a solid electrolyte layer containing a cation exchange solid electrolyte (CESE), a negative electrode coated on one surface of the solid electrolyte layer and integrated with the solid electrolyte layer, and a positive electrode coated on the other surface of the solid electrolyte layer and integrated with the solid electrolyte layer. The negative electrode contains a negative electrode catalyst and a first cation exchange binder, and the positive electrode contains a positive electrode catalyst and a second cation exchange binder; a negative electrode porous transport layer provided on the negative electrode and having porosity; a positive electrode porous transport layer provided on the positive electrode and having porosity; and an interfacial layer containing an anion exchange polymer between the positive electrode and the positive electrode porous transport layer. Water is supplied to the negative electrode through the negative electrode porous transport layer, and an oxidation reaction of water occurs at the negative electrode; carbon dioxide is supplied to the positive electrode through the positive electrode porous transport layer, and a reduction reaction of carbon dioxide occurs at the positive electrode.

[0025] As described above, the method and system suitably include the use of a controller or a processor. Other aspects and preferred embodiments of the present invention will be discussed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments shown in the accompanying drawings, which are given by way of example only and thus do not limit the present invention, wherein:

[0027] Figure 1 Shows a liquid batch cell according to the prior art;

[0028] Figure 2 Shows a flow cell according to the prior art;

[0029] Figure 3 Shows a solid electrolyte-based flow cell having an electrode-integrated porous transport layer (EIPTL);

[0030] Figure 4 Shows a cell for carbon dioxide conversion according to the present invention;

[0031] Figure 5 Shows a first embodiment of an electrode-solid electrolyte assembly according to the present invention;

[0032] Figure 6 Is a cross-sectional view taken along the Figure 5 Line A-A' of;

[0033] Figure 7 Shows a second embodiment of an electrode-solid electrolyte assembly according to the present invention;

[0034] Figure 8 Is along Figure 7 Line B-B' of the cross-sectional view taken;

[0035] Figure 9 Shows a first embodiment of a solid electrolyte layer according to the present invention;

[0036] Figure 10 Shows a second embodiment of a solid electrolyte layer according to the present invention;

[0037] Figure 11A Shows an embodiment of a negative electrode porous transport layer according to the present invention;

[0038] Figures 11B to 11D Shows Figure 11A A modified embodiment of the negative electrode porous transport layer of;

[0039] Figure 11E Shows another embodiment of a negative electrode porous transport layer according to the present invention;

[0040] Figures 11F to 11H Shows Figure 11E A modified embodiment of the negative electrode porous transport layer of;

[0041] Figure 12Shows the positive electrode porous transport layer according to the present invention;

[0042] Figure 13 Reference diagram showing the positive electrode porous transport layer according to the present invention;

[0043] Figure 14 Shows the negative electrode bipolar plate according to the present invention;

[0044] Figure 15 Shows a cross-sectional view of the negative electrode bipolar plate according to the present invention;

[0045] Figure 16 Shows the negative electrode gasket according to the present invention;

[0046] Figure 17 Shows the combination of the negative electrode gasket and the negative electrode bipolar plate according to the present invention;

[0047] Figure 18 Shows the positive electrode bipolar plate according to the present invention;

[0048] Figure 19 Shows a cross-sectional view of the positive electrode bipolar plate according to the present invention;

[0049] Figure 20 Shows the positive electrode gasket according to the present invention;

[0050] Figure 21 Shows the combination of the positive electrode gasket and the positive electrode bipolar plate according to the present invention;

[0051] Figure 22 Shows the battery stack according to the present invention;

[0052] Figure 23 Shows the end plate according to the present invention;

[0053] Figure 24 Shows along Figure 23 The cross-sectional view taken along the C-C' line. Detailed Description

[0054] Through the following preferred embodiments given with reference to the accompanying drawings, the above objects and other objects, features and advantages will be clearly understood. However, the present invention is not limited to these embodiments and can be implemented in different forms. These embodiments are presented only for a thorough and complete understanding of the disclosed content and to fully convey the technical concept of the present invention to those skilled in the art.

[0055] Throughout the description of the drawings, like reference numerals represent like elements. In the drawings, the dimensions of the structures are exaggerated for clarity. It should be understood that although terms such as "first", "second", etc. may be used herein to describe various elements, these elements should not be understood to be limited by these terms. These terms are only used to distinguish one element from another. For example, within the scope defined by the present invention, the first element may be referred to as the second element, and similarly, the second element may be referred to as the first element. The singular form may also include the plural form unless the context clearly indicates otherwise.

[0056] It should also be understood that when terms such as "comprise", "has", etc. are used in this specification, the presence of the stated features, numbers, steps, operations, elements, components or combinations thereof is indicated, but the presence or addition of one or more other features, numbers, steps, operations, elements, components or combinations thereof is not excluded. In addition, it should be understood that when an element such as a layer, film, region or substrate is referred to as being "on" another element, the element can be directly on the other element or there can also be intervening elements. It should also be understood that when an element such as a layer, film, region or substrate is referred to as being "under" another element, the element can be directly under the other element or there can also be intervening elements.

[0057] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the present invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. These terms are only intended to distinguish one component from another and do not limit the characteristics, order or sequence of the components that make up the component. As used herein, the term "and / or" includes any combination and all combinations of more than one of the associated listed items. In addition, the terms "unit", "-er", "-or" and "module" described in this specification refer to a unit for processing at least one function and operation, which can be implemented by hardware components or software components and combinations thereof.

[0058] Although the exemplary embodiments are described as using multiple units for the exemplary processes, it should be understood that the exemplary processes can also be performed by more than one module. In addition, it should be understood that the term controller / control unit refers to a hardware device that includes a memory and a processor and is specifically programmed to perform the processes described herein. The memory is configured to store modules, and the processor is specifically configured to execute the modules to perform one or more of the processes described further below.

[0059] In addition, the control logic of the present invention can be embodied as a non-transitory computer-readable medium on a computer-readable medium, which contains executable program instructions executed by a processor, a controller, etc. Examples of computer-readable media include, but are not limited to, ROM, RAM, compact disc (CD)-ROM, magnetic tape, floppy disk, flash drive, smart card, and optical data storage device. The computer-readable medium can also be distributed in computer systems connected by a network, so that the computer-readable medium is stored and executed in a distributed fashion, for example, through a telematics server or a Controller Area Network (CAN).

[0060] Unless otherwise specified or obvious from the context, the term "about" as used herein should be understood to be within the normal tolerances in the art, for example, within 2 standard deviations of the average value. "About" can be understood to be within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the specified value. Unless the context clearly dictates otherwise, all numerical values provided herein are modified by the term "about".

[0061] Unless the context clearly dictates otherwise, all numbers, values (figures), and / or expressions representing the amounts of components, reaction conditions, polymer compositions, and mixtures used in this specification are approximate values, which reflect the various measurement uncertainties inherently present when obtaining these values. Therefore, it should be understood that in all cases, the term "about" should be understood to modify all numbers, values, and / or expressions. In addition, when a numerical range is disclosed in this specification, unless otherwise defined, the range is continuous and includes all numbers (including the maximum value) from the minimum value to the maximum value of the range. In addition, when the range relates to integers, unless otherwise defined, it includes all integers from the minimum value to the maximum value of the range (including the maximum value).

[0062] In Figure 1 and Figure 2 In the conventional liquid electrolyte-based battery cells shown in, an alkaline solution such as potassium hydroxide (KOH), a neutral solution, or an acidic solution such as sulfuric acid (H2SO4) can be used as the negative electrode electrolyte and the positive electrode electrolyte.

[0063] When using an alkaline solution, carbon dioxide as the positive electrode reactant, before participating in the carbon dioxide reduction reaction, due to hydroxide ions (OH -) It is consumed and forms salts as by-products, resulting in a decrease in the efficiency and stability of the battery cell. In addition, as the costs of alkaline and neutral solutions and equipment maintenance increase, the overall cost of the battery cell increases, and the operating devices within the system become complex. Using acidic solutions can minimize the problem of salt formation, but there are still additional costs for acidic solutions and equipment maintenance, as well as the problem of complex operating equipment within the system.

[0064] Therefore, to solve the above problems, the present invention provides a method in which a solid electrolyte is used instead of a liquid electrolyte in the internal structure of the battery cell, while using deionized water as the negative electrode reactant and humidified CO2 gas as the positive electrode reactant.

[0065] Figure 4 Fig. 10 shows a battery cell 10 for carbon dioxide conversion. The battery cell 10 for carbon dioxide conversion may include: an electrode-solid electrolyte assembly 100 including a solid electrolyte layer 110, a negative electrode 120, and a positive electrode 130; a negative electrode porous transport layer (PTL) 200 provided on one surface of the electrode-solid electrolyte assembly 100; a positive electrode porous transport layer (PTL) 300 provided on the other surface of the electrode-solid electrolyte assembly 100; an interface layer 800 interposed between the positive electrode 130 and the positive electrode porous transport layer 300; a negative electrode bipolar plate 400 provided on the negative electrode porous transport layer 200; a negative electrode gasket 500 mounted on the negative electrode bipolar plate 400 outside the negative electrode porous transport layer 200; a positive electrode bipolar plate 600 provided on the positive electrode porous transport layer 300; and a positive electrode gasket 700 mounted on the positive electrode bipolar plate 600 outside the positive electrode porous transport layer 300.

[0066] The electrochemical reaction proceeds as follows in the electrochemical battery cell 10. Water is supplied to the negative electrode 120 through the negative electrode flow channel 430 and the negative electrode porous transport layer 200, and an oxidation reaction of water occurs at the negative electrode 120. Humidified carbon dioxide is supplied to the positive electrode 130 through the positive electrode flow channel 630 and the positive electrode porous transport layer 300, and a reduction reaction of carbon dioxide occurs at the positive electrode 130.

[0067] As a result of the carbon dioxide reduction reaction, at least one product selected from the group consisting of formic acid, ethylene, propylene, alcohols, and combinations thereof can be obtained. This will be described later.

[0068] The electrode-solid electrolyte assembly 100 may include a solid electrolyte layer 110, a negative electrode 120 coated on one surface of the solid electrolyte layer 110 and integrated with the solid electrolyte layer 110, and a positive electrode 130 coated on the other surface of the solid electrolyte layer 110 and integrated with the solid electrolyte layer 110.

[0069] As used herein, the term "integration" refers to a state in which elements are firmly bonded by directly coating raw materials of the negative electrode 120 and / or the positive electrode 130 onto the solid electrolyte layer 110, transferring the negative electrode 120 and / or the positive electrode 130 onto the solid electrolyte layer 110, or attaching the negative electrode 120 and / or the positive electrode 130 to the solid electrolyte layer 110, and then pressing the resulting product under high pressure. The bonding force or peel strength between the elements of the electrode-solid electrolyte assembly 100 can be stronger than the bonding force or peel strength between the electrode-solid electrolyte assembly 100 and the negative electrode porous transport layer 200 and / or the positive electrode porous transport layer 300. The above Figure 3 The solid electrolyte-based flow cell having the EIPTL includes a five-layer laminate based on the EIPTL structure, in which the electrode and the porous transport layer are directly integrated, rather than the electrode and the solid electrolyte that play important roles in the electrochemical reaction, thus causing problems such as deterioration of the electrochemical reactivity and durability of the cell, and overflow of liquid products and / or water as the current density of the cell increases. The present invention is characterized by using a three-layer assembly, in which the negative electrode 120 and the positive electrode 130 are integrated into the solid electrolyte layer 110 rather than the porous transport layer. By directly assembling the negative electrode 120 and the positive electrode 130 on the solid electrolyte layer 110, the contact resistance between them can be greatly reduced, and the electrochemical reaction rate can be increased. In addition, during the operation of the cell, the durability and stability against the repetitive contraction-expansion degradation mode of the solid electrolyte layer 110 caused by temperature / relative humidity (RH) changes and the freeze / thaw degradation mode caused by seasonal changes can be improved. At the same time, different from the conventional solid electrolyte-based EIPTL type flow cell structure, the electrode paste is directly coated on the solid electrolyte layer 110, so the problem that the electrode paste clogs the pores of the porous transport layer, thus reducing the mass transfer performance, can be solved.

[0070] Figure 5 Shows a first embodiment of the electrode-solid electrolyte assembly 100 according to the present invention. Figure 6 is along Figure 5A cross-sectional view taken along line A-A'. The solid electrolyte layer 110 may include a central portion in contact with the negative electrode 120 and the positive electrode 130, and an edge portion other than the central portion. The electrode-solid electrolyte assembly 100 may include a protective member 140 located at the edge portion. Specifically, the negative electrode protective member 141 may be installed in a region defined by one surface of the edge portion and the side surface of the negative electrode 120. The positive electrode protective member 142 may be installed in a region defined by the other surface of the edge portion and the side surface of the positive electrode 130.

[0071] The protective member 140 can improve the durability of the solid electrolyte layer 110 by delaying the deterioration of the solid electrolyte layer 110 during the operation of the battery cell, and can improve the durability of the battery cell by delaying the deterioration of the negative electrode 120 and the positive electrode 130 caused by the deterioration of the solid electrolyte layer 110. In addition, the conventional structure without the protective member 140 has the following problems: when handling components during the manufacturing of the battery cell and the battery cell stack, it directly contacts the solid electrolyte layer with low rigidity and flexibility, so it is contaminated, resulting in the problem of deteriorated handling performance. On the other hand, when using the protective member 140 as in the present invention, when handling the solid electrolyte layer 110, etc., contamination can be fundamentally prevented, and due to its high rigidity, the handling performance can be improved.

[0072] The protective member 140 may include a material having excellent heat resistance and chemical resistance. Specifically, under the measurement conditions of ISO 178 (measurement speed: 2 mm / min) established by the ISO (International Standardization Organization), the flexural modulus of the protective member 140 is 1 GPa or more, preferably 1.5 GPa or more. Under the measurement conditions of ISO 75 (measurement pressure: 1.8 MPa), the protective member 140 may have a heat deflection (or distortion) temperature of 60 °C or more, preferably 80 °C or more. The protective member 140 satisfying these characteristics may include at least one selected from polyimide (PI), polyetherimide (PEI), polyphenylene oxide (PPO), poly(phenyleneether) (PPE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), poly(trimethylene terephthalate) (PTT), polyethylene naphthalate (PEN), poly(ether ether ketone) (PEEK), and combinations thereof. The protective member 140 should have a uniform surface to ensure the airtightness of the battery cell. Therefore, if possible, the protective member 140 is preferably made of only a polymer, rather than a mixture of a polymer and an inorganic substance such as a filler.

[0073] The electrode-solid electrolyte assembly 100 may include an adhesive member 150 interposed between the protective member 140 and the solid electrolyte layer 110 to connect the protective member 140 to the solid electrolyte layer 110.

[0074] The adhesive member 150 can be prepared by applying an adhesive to the surface of the protective member 140 and then drying. The adhesive member 150 can include polar adhesives such as silicone, epoxy, or acryl; non-polar adhesives such as polyethylene (PE), polypropylene (PP), poly(ethylene-co-propylene), or ethylene-propylene rubber (EPR); modified adhesives in which polar groups are introduced into non-polar adhesives, such as poly(ethylene-graft-maleic anhydride), poly(propylene-graft-maleic anhydride), chlorinated polyethylene, or chlorinated polypropylene, or combinations thereof.

[0075] The protective member 140 provided with the adhesive member 150 is mounted on the edge of the solid electrolyte layer 110, and then it is attached to the solid electrolyte layer 110 by compression-molding at a predetermined pressure and a temperature of about 70 °C to 240 °C or 100 °C to 200 °C. When the temperature is lower than 70 °C, the protective member 140 may not be well bonded, and when the temperature exceeds 240 °C, the materials contained in the solid electrolyte layer 110, the negative electrode 120, the positive electrode 130, etc. may deteriorate.

[0076] Figure 7 Shows a second embodiment of the electrode-solid electrolyte assembly 100' according to the present invention. Figure 8 Shows along Figure 7 A cross-sectional view taken along the line B-B'. In the second embodiment, the protective member 140' is located in the region defined by one surface of the solid electrolyte layer 110 and the side surface of the negative electrode 120 and the region defined by the other surface of the solid electrolyte layer 110 and the side surface of the positive electrode 130, and the protective member 140' covers the side surface of the solid electrolyte layer 110.

[0077] The protective member 140' may include at least one selected from the group consisting of polyimide (PI), polyetherimide (PEI), polyphenylene oxide (PPO), polyphenylene ether (PPE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), polyetheretherketone (PEEK), polyethylene (PE), polypropylene (PP), poly(ethylene-co-propylene), ethylene-propylene rubber (EPR), poly(ethylene-grafted-maleic anhydride), poly(propylene-grafted-maleic anhydride), chlorinated polyethylene, chlorinated polypropylene, and combinations thereof. Meanwhile, the protective member 140' may further include fillers such as glass fiber and carbon fiber to enhance physical properties. The content of the filler is not particularly limited and may be 5 wt% to 50 wt% or 10 wt% to 35 wt% based on the total weight of the protective member 140'. When the content of the filler is less than 5 wt%, the effect of enhancing physical properties may be insufficient, while when its content exceeds 50 wt%, the properties of the polymer may deteriorate and the melt processability may decline.

[0078] The protective member 140' can be prepared by injection molding on the outer portion of the assembly of the solid electrolyte layer 110, the negative electrode 120, and the positive electrode 130. In addition, the adhesive member 150' can be coated on the surface of the protective member 140'. The adhesive member 150' can be used to bond the electrode-solid electrolyte assembly 100 to the negative electrode porous transport layer 200 and the positive electrode porous transport layer 300. The type of the adhesive member 150' is the same as described above.

[0079] The solid electrolyte layer 110 may contain a cation-exchange solid electrolyte (CESE). Examples of solid electrolytes commonly used in electrochemical cells may include an anion-exchange solid electrolyte (AESE), a cation-exchange solid electrolyte, a bipolar solid electrolyte (BPSE), etc.

[0080] The anion-exchange solid electrolyte can exchange anions such as hydroxide ions (OH - ) etc. The backbone of the anion-exchange solid electrolyte usually contains hydrocarbons rather than fluorinated materials. Representative anion-exchange solid electrolytes may include: Sustainion based on polystyrene tetramethylimidazolium chloride containing polystyrene (PS) as the main chain and containing an imidazolium group TM, benzimidazolium-based solid electrolytes represented by Formula 1 below, poly(aryl piperidinium)-based solid electrolytes represented by Formula 2 below, etc. Alternatively, the anion exchange solid electrolyte may include commercially available Sustainion TM , Aemion TM , PiperION TM , etc.

[0081] [Formula 1]

[0082]

[0083] where n can be from 10 to 1000.

[0084] [Formula 2]

[0085]

[0086] where x can be from 10 to 1000 and y can be from 10 to 1000.

[0087] Anion exchange solid electrolytes are widely used because they are suitable for carrying out the carbon dioxide reduction reaction on the positive electrode of a conventional electrochemical cell to convert carbon dioxide. However, carbon dioxide as the positive electrode reactant reacts with hydroxide ions and is consumed, which disadvantageously leads to the formation and precipitation of salts as by-products at the positive electrode, and causes deterioration of the cell performance and durability. The by-products permeate from the positive electrode to the negative electrode through the anion exchange solid electrolyte, resulting in the problem of reduced carbon dioxide (CO2) utilization rate. In addition, due to the low durability during the oxygen evolution reaction (OER) at the negative electrode, the anion exchange solid electrolyte has the problem of oxidative degradation. Due to these conventional problems, most anion exchange solid electrolytes have the disadvantages of low durability and being extremely unsuitable for large-scale manufacturing. For example, Sustainion TM has poor handling performance because it should be stored in a state of being immersed in potassium hydroxide (KOH) before use, and due to the complex sample processing process, the large-scale production efficiency is low.

[0088] To solve these problems, recently, the interest in cation exchange solid electrolytes has increased significantly. Cation exchange solid electrolytes have a history of use in industries such as chlor-alkali electrolysis for several decades, and their large-scale production and durability have been proven.

[0089] Generally speaking, cation-exchange solid electrolytes have great advantages in increasing the conversion rate of carbon dioxide because they have high durability and stability under various electrochemical operating conditions, and can inhibit the permeation (crossover) of reactants or products from the positive electrode to the negative electrode. In addition, by using the solid electrolyte layer 110 containing a cation-exchange solid electrolyte according to the present invention and using deionized water as the negative electrode reactant at the same time, the advantages of suppressing the accumulation of unwanted impurities or by-products at the positive electrode and increasing the single pass conversion (SPC) efficiency can be obtained.

[0090] The cation-exchange solid electrolyte may include a fluorinated solid electrolyte and / or a hydrocarbon solid electrolyte.

[0091] The fluorinated solid electrolyte may contain a per-fluorinated sulfonic acid (PFSA) compound. The PFSA compound has the advantages of high proton conductivity, excellent mechanical properties, chemical resistance, durability and processability, and can be mass-produced. PFSA-based compounds are roughly classified into Nafion with long side chains according to their side chain structures TM , Dynyon with medium side chains TM and Aquivion with short side chains TM . In addition, the PFSA-based compound may include sulfonic acid, carboxylic acid, etc. as functional groups at the ends of the side chains.

[0092] The equivalent weight (EW) of the functional group of the PFSA compound may be about 600 g / mol to 1000 g / mol or about 700 g / mol to 950 g / mol. When the equivalent weight of the functional group is less than 600 g / mol, the solid electrolyte layer 110 may swell excessively in water, and the mechanical properties may decrease due to the excessive content of the functional group. When the equivalent weight of the functional group is higher than 1000 g / mol, the ion exchange capacity of the solid electrolyte layer 110 may deteriorate due to the too low content of the functional group.

[0093] Compared with fluorinated solid electrolytes, hydrocarbon solid electrolytes can be based on compounds that are easier to polymerize or copolymerize various molecular structures. Hydrocarbon solid electrolytes include sulfonated polyethylene, sulfonated polypropylene, sulfonated polystyrene, sulfonated polysulfone, sulfonated polybenzimidazole, sulfonated poly(phenylene oxide), sulfonated poly(phenylene ether), sulfonated poly(arylene ether ketone), sulfonated polyether ether ketone, sulfonated polyether ketone, sulfonated polyimide, sulfonated polyetherimide, sulfonated poly(styrene-b-ethylene-r-butadiene-b-styrene)tri-block copolymer, etc., which contain sulfonic acid groups.

[0094] Figure 9 Shows a first embodiment of the solid electrolyte layer 110 according to the present invention. Figure 10 Shows a second embodiment of the solid electrolyte layer according to the present invention. Refer to Figure 9 and Figure 10 , the solid electrolyte layer 110 includes at least one reinforcing layer 111 containing pores filled with a first cation-exchange solid electrolyte and an ion-exchange layer 112 disposed on at least one surface of the reinforcing layer 111 and containing a second cation-exchange solid electrolyte. The first cation-exchange solid electrolyte and the second cation-exchange solid electrolyte can be the same as or different from each other.

[0095] The present invention is characterized in that the physical durability is improved by introducing the reinforcing layer 111 into the solid electrolyte layer 110.

[0096] The reinforcing layer 111 can include one to four layers or one or two layers. Without the reinforcing layer 111, the effect of strengthening the solid electrolyte cannot be obtained. When the reinforcing layer 111 includes more than four layers, the process of manufacturing the solid electrolyte layer 110 will become complicated.

[0097] When the first cation-exchange solid electrolyte is a fluorinated solid electrolyte, the reinforcing layer 111 can include porous expanded poly(tetrafluoroethylene) (porous e-PTFE).

[0098] When the first cation-exchange solid electrolyte is a hydrocarbon solid electrolyte, the reinforcing layer 111 may include a porous membrane made of polyimide (PI), polyetherimide (PEI), polyetheretherketone (PEEK), polyethylene naphthalate (PEN), or polyethersulfone (PES), or a combination thereof.

[0099] The porosity of the reinforcing layer 111 may be about 20% to 90% or about 40% to 80%. When the porosity is less than 20%, it is difficult to sufficiently impregnate the reinforcing layer 111 with the first cation-exchange solid electrolyte and bind them to each other; when the porosity exceeds 80%, the mechanical properties of the reinforcing layer 111 will be greatly reduced, and the effect of introducing the reinforcing layer cannot be obtained.

[0100] For example, the solid electrolyte layer 110 can be achieved by adding fillers such as polymer fibers or glass fibers to the cation-exchange solid electrolyte, without the reinforcing layer 111, but not limited thereto.

[0101] The thickness of the solid electrolyte layer 110 may be about 5 μm to 100 μm or about 8 μm to 70 μm. When the thickness is less than 5 μm, there are problems of greatly reduced mechanical properties and greatly increased crossover of cell reactants / products. On the other hand, when the thickness exceeds 100 μm, the ohmic resistance of the solid electrolyte layer 110 may increase, and with the increase of overpotential, the cell performance may decline.

[0102] Based on the total volume of the solid electrolyte layer 110, the volume of the reinforcing layer 111 may be about 10 vol% to 70 vol% or about 20 vol% to 50 vol%. When the volume of the reinforcing layer 111 is less than 10 vol%, the effect of strengthening the solid electrolyte layer 110 may be insufficient; when its volume exceeds 70 vol%, the content of the cation-exchange solid electrolyte in the solid electrolyte layer 110 may decrease, and the ion-exchange capacity of the solid electrolyte layer 110 may be greatly reduced.

[0103] Hydrogen peroxide (HOOH) can be generated according to the structure and operating conditions of the electrochemical cell 10. Generally, hydrogen peroxide generates highly reactive oxygen-containing radicals such as hydroxyl radicals (·OH) and hydroperoxyl radicals (·OOH). These radicals attack the cation-exchange solid electrolyte in the solid electrolyte layer 110, the first cation-exchange binder in the negative electrode 120, and the second cation-exchange binder in the positive electrode 130, resulting in chemical degradation of the electrode-solid electrolyte assembly 100 and deterioration of the long-term durability of the electrochemical cell 10 for carbon dioxide conversion.

[0104] The present invention is characterized in that an antioxidant is added to the solid electrolyte layer 110 to alleviate or inhibit chemical degradation. Specifically, the antioxidant can be dispersed in the ion exchange layer 112.

[0105] The antioxidant can include a primary antioxidant as a free radical scavenger or quencher and a secondary antioxidant as a hydrogen peroxide decomposer.

[0106] When using a fluorinated solid electrolyte as the cation exchange solid electrolyte, a cerium antioxidant can be used as the primary antioxidant. The cerium antioxidant can include cerium oxide (or ceria: CeO x ), modified cerium oxide, cerium(III) nitrate hexahydrate (Ce(NO3)3·6H2O), etc. The modified cerium oxide can include cerium-zirconium oxide (CeZrO x ), cerium-manganese oxide (CeMnO x ), gadolinium (Gd)- or samarium (Sm)-doped cerium oxide, etc.

[0107] Cerium antioxidants can be introduced in the form of particles or powders (nanoparticles or nanopowders) with a grain size of a few nanometers or dozens of nanometers. However, cerium oxide and modified cerium oxide should be pre-dispersed before being added to the fluorinated solid electrolyte because they are usually stored in an agglomerated state after production. To improve the degree of dispersion and / or distribution, a surfactant can be introduced together with the cerium antioxidant, which may reduce the activity of the cerium antioxidant. Therefore, to improve the dispersibility and activity of the cerium antioxidant, the cerium antioxidant can be introduced in the form of being loaded on a carrier. The carrier can include titanium dioxide (TiO2), silica (SiO2), carbon powder, carbon nanotubes (CNT), etc. Based on the total weight of the carrier and the cerium antioxidant, the content of the cerium antioxidant loaded on the carrier can be about 2 wt% to 70 wt% or about 10 wt% to 50 wt%. When the content of the cerium antioxidant is less than 2 wt%, its antioxidant performance may deteriorate due to the excessive content of the carrier compared with the cerium antioxidant. When the content exceeds 70 wt%, the cerium antioxidant is distributed too densely on the carrier, making it difficult to effectively load and use the cerium antioxidant.

[0108] Based on the total weight of the cation-exchange solid electrolyte and the antioxidant in the solid electrolyte layer 110, the content of the cerium antioxidant can be about 200 ppm to 50,000 ppm or about 1,000 ppm to 10,000 ppm. When the content of the cerium antioxidant is less than 200 ppm, the antioxidant performance will be greatly reduced, while when the content exceeds 50,000 ppm, it is difficult for the cerium antioxidant to be uniformly dispersed in the solid electrolyte layer 110, and the physical properties such as the ionic conductivity of the solid electrolyte layer 110 will decrease and the cost will also increase.

[0109] In the cerium antioxidant, cerium oxide and modified cerium oxide can have a grain size of about 2 nm to 100 nm or about 10 nm to 50 nm measured by X-ray. When the grain size is less than 2 nm, the cerium antioxidant particles may agglomerate during the operation of the battery cell, the activity of the cerium antioxidant may decrease over time, and the long-term durability of the cerium antioxidant may decrease. On the other hand, when the grain size exceeds 100 nm, the initial activity of the cerium antioxidant may be too low.

[0110] When using a fluorinated solid electrolyte as the cation-exchange solid electrolyte, the secondary antioxidant can be, for example, a manganese antioxidant such as manganese oxide, a non-manganese transition metal antioxidant such as platinum (Pt), gold (Au), or palladium (Pd), or a combination thereof.

[0111] To increase the dispersibility and activity of the secondary antioxidant, the secondary antioxidant can be loaded on a carrier. The carrier is as described above. Here, the content of the secondary antioxidant loaded on the carrier and the content of the secondary antioxidant based on the total weight of the cation-exchange solid electrolyte and the antioxidant in the solid electrolyte layer 110 are as described for the cerium antioxidant.

[0112] When using a hydrocarbon solid electrolyte as the cation-exchange solid electrolyte, a sterically-hindered phenolic antioxidant can be used as the primary antioxidant. Specifically, the sterically-hindered phenolic antioxidant can include Irganox 1010 containing pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) TM 、Irganox 1076 containing octadecyl-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) TM 、Irganox 245 containing ethylene bis(oxyethylene)bis-(3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate) TM and so on.

[0113] Based on the total weight of the cation-exchange solid electrolyte and the antioxidant in the solid electrolyte layer 110, the content of the sterically-hindered phenolic antioxidant can be about 200 ppm to 50000 ppm or about 1000 ppm to 10000 ppm. When the content of the sterically-hindered phenolic antioxidant is less than 200 ppm, the antioxidant performance will be greatly reduced, while when the content of the sterically-hindered phenolic antioxidant exceeds 50000 ppm, it is difficult for the phenolic antioxidant to be evenly dispersed, the ionic conductivity and the overall physical properties of the solid electrolyte layer 110 will decrease and the cost will also increase.

[0114] When using a hydrocarbon solid electrolyte as the cation-exchange solid electrolyte, a phosphite antioxidant can be used as the secondary antioxidant. The phosphite antioxidant can include Irgafos 168 containing tris(2,4-di-tert-butylphenyl) phosphite TMHere, based on the total weight of the cation-exchange solid electrolyte and the antioxidant in the solid electrolyte layer 110, the content of the phosphite antioxidant is as described for the phenolic antioxidant.

[0115] As shown in Reaction Scheme 1 below, the negative electrode 120 can use water (H2O) as a reactant and cause an oxidation reaction of water, thereby generating oxygen (O2).

[0116] [Reaction Formula 1]

[0117] H2O → 1 / 2O2 + 2H + + 2e -

[0118] The water supplied to the negative electrode 120 can be deionized water with a specific resistance of 18 MΩ·cm or more. When the specific resistance of the deionized water falls within the above range, the purity of the deionized water can be maintained.

[0119] The negative electrode 120 can include a negative electrode catalyst, a first cation-exchange binder, a negative electrode antioxidant, and the like.

[0120] The negative electrode catalyst can increase the rate of the oxygen evolution reaction (OER). The negative electrode catalyst can include at least one selected from the group consisting of iridium oxide (IrOx), ruthenium oxide (RuOx), and combinations thereof.

[0121] The loading amount of the platinum group metal (PGM) in the negative electrode catalyst can be about 2.0 mg-PGM / cm 2 or less or about 0.5 mg-PGM / cm 2 or less. When the loading amount exceeds 2.0 mg-PGM / cm 2 , the cost increases significantly, the process of producing a uniform negative electrode from the anode catalyst ink is difficult, and the uniform dispersion of the negative electrode catalyst in the negative electrode is also difficult.

[0122] To increase the dispersion of the negative electrode catalyst, the negative electrode catalyst can be supported on a carrier. The carrier is preferably a non-carbon material that can be used under high potential conditions of 2 V or more, and examples thereof include tin(IV) oxide (SnO2), titanium (Ti)-doped tin oxide (Ti-doped SnO2), antimony (Sb)-doped tin oxide (Sb-doped SnO2), nanostructured thin film (NSTF), titanium dioxide (TiO2), silica (SiO2), etc. Based on the total content of the negative electrode catalyst and the carrier, the loading ratio of the negative electrode catalyst can be about 10% by weight to 70% by weight or about 20% by weight to 50% by weight. When the loading ratio is less than 10% by weight, the loading effect may be insufficient, while when the loading ratio exceeds 70% by weight, the negative electrode catalyst may be too densely distributed on the carrier, which may reduce the efficiency of the oxygen evolution reaction of the negative electrode.

[0123] The first cation exchange binder can include a fluorinated solid electrolyte and / or a hydrocarbon solid electrolyte.

[0124] The fluorinated solid electrolyte can contain a perfluorosulfonic acid (PFSA) compound. The PFSA compound has advantages such as high proton conductivity, excellent mechanical properties, chemical resistance, durability, and processability, and can be mass-produced. PFSA-based compounds are roughly classified into Nafion with a long side chain according to their side chain structure TM , Dynyon with a medium side chain TM and Aquivion with a short side chain TM . In addition, the PFSA-based compound can include sulfonic acid, carboxylic acid, etc. as functional groups at the end of the side chain.

[0125] The equivalent weight (EW) of the functional group of the PFSA compound can be about 600 g / mol to 1100 g / mol or about 700 g / mol to 950 g / mol. When the equivalent weight of the functional group is less than 600 g / mol, due to the excessive content of the functional group, the negative electrode 120 may swell excessively in water and the mechanical properties may deteriorate. On the other hand, when the equivalent weight of the functional group is higher than 1100 g / mol, due to the low content of the functional group, the ion exchange capacity of the negative electrode 120 may deteriorate.

[0126] Compared with fluorinated solid electrolytes, hydrocarbon solid electrolytes can be based on compounds that are more easily polymerized or copolymerized into various molecular structures. Hydrocarbon solid electrolytes include sulfonated polyethylene, sulfonated polypropylene, sulfonated polystyrene, sulfonated polysulfone, sulfonated polybenzimidazole, sulfonated polyphenylene ether, sulfonated polyarylene ether ketone, sulfonated polyether ether ketone, sulfonated polyether ketone, sulfonated polyimide, sulfonated polyetherimide, sulfonated poly(styrene-b-ethylene-r-butadiene-b-styrene) triblock copolymer, etc., which contain sulfonic acid groups.

[0127] The first cation exchange binder can be the same as or different from the cation exchange solid electrolyte contained in the solid electrolyte layer 110, and preferably it is the same as the cation exchange solid electrolyte.

[0128] A negative electrode antioxidant is included in the first cation exchange binder to mitigate or inhibit the chemical degradation of the negative electrode 120. The negative electrode antioxidant can include a primary antioxidant and / or a secondary antioxidant.

[0129] When a fluorinated solid electrolyte is used as the first cation exchange binder, the negative electrode antioxidant can be a cerium antioxidant as the primary antioxidant. The cerium antioxidant can include cerium oxide (or ceria: CeO x ), modified cerium oxide, or cerium(III) nitrate hexahydrate (Ce(NO3)3·6H2O), etc. The modified cerium oxide can include cerium-zirconium oxide (CeZrO x ), cerium-manganese oxide (CeMnO x ), gadolinium (Gd)- or samarium (Sm)-doped cerium oxide, etc.

[0130] Cerium antioxidants can be introduced in the form of particles or powders (nanoparticles or nanopowders) with a grain size of several nanometers or dozens of nanometers. However, cerium oxide and modified cerium oxide should be pre-dispersed before being added to the fluorinated solid electrolyte because they are usually stored in an agglomerated state after production. To improve the degree of dispersion and / or distribution, surfactants can be introduced together with the cerium antioxidants, which may reduce the activity of the cerium antioxidants. Therefore, to improve the dispersibility and activity of the cerium antioxidants, the cerium antioxidants can be introduced in the form of being supported on a carrier. The carrier can include titanium dioxide (TiO2), silica (SiO2), carbon powder, carbon nanotubes (CNT), etc. Based on the total weight of the carrier and the cerium antioxidants, the content of the cerium antioxidants supported on the carrier can be about 2 wt% to 70 wt% or about 10 wt% to 50 wt%. When the content of the cerium antioxidants is less than 2 wt%, the antioxidant performance may deteriorate due to the excessive content of the carrier compared with the cerium antioxidants. On the other hand, when the content exceeds 70 wt%, the cerium antioxidants are distributed too densely on the carrier, making it difficult to effectively load and use the cerium antioxidants.

[0131] Based on the total weight of the first cation-exchange binder and the antioxidant in the negative electrode 120, the content of the cerium antioxidant can be about 200 ppm to 50,000 ppm or about 1,000 ppm to 10,000 ppm. When the content of the cerium antioxidant is less than 200 ppm, the antioxidant performance will be greatly reduced; while when the content exceeds 50,000 ppm, it is difficult for the cerium antioxidant to be uniformly dispersed in the negative electrode 120, and the ionic conductivity and other physical properties of the negative electrode 120 will decline and the cost will also increase.

[0132] In the cerium antioxidants, cerium oxide and modified cerium oxide can have a grain size of about 2 nm to 100 nm or about 10 nm to 50 nm measured by X-ray. When the grain size is less than 2 nm, the cerium antioxidant particles may agglomerate during the operation of the battery cell, the activity of the cerium antioxidants may decrease over time, and the long-term durability of the cerium antioxidants may decrease. On the other hand, when the grain size exceeds 100 nm, the initial activity of the cerium antioxidants may be too low.

[0133] When using a fluorinated solid electrolyte as the first cation-exchange binder, the negative electrode antioxidant can be a manganese antioxidant such as manganese oxide, a non-manganese transition metal antioxidant such as platinum (Pt), gold (Au), or palladium (Pd), or a combination thereof as a secondary antioxidant.

[0134] To increase the dispersibility and activity of the secondary antioxidant, the secondary antioxidant can be loaded on a carrier. The carrier is as described above. Here, the content of the secondary antioxidant loaded on the carrier and the content of the secondary antioxidant based on the total weight of the first cation exchange binder and the antioxidant in the negative electrode 120 are as described for the cerium antioxidant.

[0135] When a hydrocarbon solid electrolyte is used as the first cation exchange binder, the negative electrode antioxidant can be a sterically hindered phenolic antioxidant as the main antioxidant. Specifically, the sterically hindered phenolic antioxidant can include Irganox 1010 containing pentaerythritol tetra(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) TM and Irganox 1076 containing octadecyl-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) TM and Irganox 245 containing ethylene bis(oxyethylene) bis-(3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate). TM etc.

[0136] Based on the total weight of the first cation exchange binder and the antioxidant in the negative electrode 120, the content of the sterically hindered phenolic antioxidant can be about 200 ppm to 50,000 ppm or about 1,000 ppm to 10,000 ppm. When the content of the sterically hindered phenolic antioxidant is less than 200 ppm, the antioxidant performance will be greatly reduced; while when the content of the sterically hindered phenolic antioxidant exceeds 50,000 ppm, it is difficult for the phenolic antioxidant to be evenly dispersed, and the ionic conductivity and overall physical properties of the negative electrode 120 will decrease and the cost will also increase.

[0137] When a hydrocarbon solid electrolyte is used as the first cation exchange binder, the negative electrode antioxidant can be a phosphite antioxidant as the secondary antioxidant. The phosphite antioxidant can include Irgafos 168 containing tris(2,4-di-tert-butylphenyl) phosphite. TM Here, based on the total weight of the first cation exchange binder and the antioxidant in the negative electrode 120, the content of the phosphite antioxidant is the same as the content of the phenolic antioxidant.

[0138] Based on the total weight of the negative electrode 120, the content of the first cation exchange binder can be about 10 wt% to 70 wt% or about 20 wt% to 50 wt%. When the content of the first cation exchange binder is less than 10 wt%, the binding of the negative electrode catalyst is insufficient, the negative electrode 120 is delaminated, and the performance of effectively transporting the cations generated in the negative electrode 120 to the solid electrolyte layer 110 may deteriorate. On the other hand, when the content exceeds 70 wt%, the resistance within the negative electrode 120 increases, and the pores become too small, resulting in an increase in the mass transport resistance within the negative electrode 120.

[0139] The thickness of the negative electrode 120 can be about 1 μm to 30 μm or about 2 μm to 20 μm. When the thickness of the negative electrode 120 is less than 1 μm, it may be difficult to uniformly coat the negative electrode 120 on the solid electrolyte layer 110 due to its too small thickness; while when the thickness of the negative electrode 120 exceeds 30 μm, the cell resistance may increase and the performance may decline due to its too large thickness.

[0140] As shown in the following Reaction Schemes 2 to 7, the positive electrode 130 can use carbon dioxide as a reactant and cause at least one reduction reaction of carbon dioxide to produce a product.

[0141] [Reaction Scheme 2]

[0142] CO2 + 2H + + 2e - → CO (gas) + H2O

[0143] [Reaction Scheme 3]

[0144] CO2 + 2H + + 2e - → HCOOH (liquid)

[0145] [Reaction Scheme 4]

[0146] CO2 + 6H + + 6e - → CH3OH (liquid) + H2O

[0147] [Reaction Scheme 5]

[0148] 2CO2 + 12H + + 12e - → C2H4 (gas) + 4H2O

[0149] [Reaction Scheme 6]

[0150] 2CO2 + 12H + + 12e -→ C2H5OH (liquid) + 3H2O

[0151] [Reaction Scheme 7]

[0152] 3CO2 + 18H + + 18e - → C3H7OH (liquid) + 5H2O

[0153] However, the reduction reaction of carbon dioxide is not limited to the above Reaction Schemes 2 to 7, and other reactions may occur depending on the type of the positive electrode catalyst, operating conditions, etc.

[0154] The carbon dioxide can be humidified carbon dioxide with a relative humidity of about 10% to 90% or about 30% to 70%. When the relative humidity of the carbon dioxide is less than 10%, dehydration of the electrode-solid electrolyte assembly 100 may be severe, resulting in an increase in ohmic resistance and a decrease in cell performance. On the other hand, when the relative humidity of the carbon dioxide exceeds 90%, water vapor is likely to condense into liquid water due to easy supersaturation, so the water clogs the pores of the positive electrode 130 and the pores of the positive electrode porous transport layer 300, thus causing water overflow.

[0155] The positive electrode 130 can include a positive electrode catalyst, a second cation exchange binder, a positive electrode antioxidant, etc.

[0156] The positive electrode catalyst can include at least one selected from the group consisting of copper (Cu), cadmium (Cd), indium (In), tin (Sn), mercury (Hg), thallium (Tl), lead (Pb), bismuth (Bi), metal organic framework (MOF), and combinations thereof.

[0157] The type of the positive electrode catalyst can vary according to the type of the product obtained through the reduction reaction of carbon dioxide.

[0158] When the desired product is carbon monoxide, the positive electrode catalyst can include a gold (Au)-based, silver (Ag)-based, or zinc (Zn)-based catalyst.

[0159] When the desired product is a multi-carbon (C 2+ ) gas ethylene (C2H4), the positive electrode catalyst can include a copper (Cu)-based catalyst.

[0160] When the desired product is formic acid (HCOOH) or formate, the positive electrode catalyst can include a cadmium (Cd)-based, indium (In)-based, tin (Sn)-based, mercury (Hg)-based, thallium (Tl)-based, lead (Pb)-based, bismuth (Bi)-based, or metal organic framework (MOF)-based catalyst.

[0161] The indium-based catalyst may include indium oxide. The tin-based catalyst may be tin (Sn), tin oxide (SnOx), a tin alloy, a mixture thereof, or an alloy thereof. The bismuth-based catalyst may be a bismuth nanoflake, a bismuth nanowire, a bismuth nanosheet, bismuth nanoparticles immobilized in nitrogen-doped porous carbon, a mixture thereof, or an alloy thereof.

[0162] When the desired product is an alcohol such as methanol (CH3OH), ethanol (C2H5OH), or propanol (C3H7OH), the positive electrode catalyst may include a copper (Cu)-based catalyst.

[0163] The loading amount of the positive electrode catalyst may be about 5.0 mg / cm 2 or about 2.0 mg / cm 2 or less. When the loading amount of the positive electrode catalyst exceeds 5.0 mg / cm 2 the cost increases significantly, the process of producing a uniform positive electrode from the positive electrode catalyst slurry is difficult, and the uniform dispersion of the positive electrode catalyst within the positive electrode is also difficult.

[0164] To increase the dispersibility of the positive electrode catalyst, the positive electrode catalyst may be loaded on a support. Based on the total content of the positive electrode catalyst and the support, the support ratio of the positive electrode catalyst may be about 10 wt% to 70 wt% or about 20 wt% to 50 wt%. When the support ratio is less than 10 wt%, the loading effect may be insufficient, while when the support ratio exceeds 70 wt%, the positive electrode catalyst may be too densely distributed on the support, which may reduce the efficiency of the carbon dioxide reduction reaction.

[0165] The second cation exchange binder may include a fluorinated solid electrolyte and / or a hydrocarbon solid electrolyte.

[0166] The fluorinated solid electrolyte may contain a perfluorosulfonic acid (PFSA) compound. PFSA compounds have advantages such as high proton conductivity, excellent mechanical properties, chemical resistance, durability, and processability, and can be mass-produced. PFSA-based compounds are roughly classified into Nafion with long side chains TM Dynyon with medium side chains TM and Aquivion with short side chains TM . In addition, PFSA-based compounds may include sulfonic acid, carboxylic acid, etc. as functional groups at the ends of the side chains.

[0167] The equivalent weight (EW) of the functional groups of the PFSA compound can be about 600 g / mol to 1100 g / mol or about 700 g / mol to 950 g / mol. When the equivalent weight of the functional groups is less than 600 g / mol, due to the excessive content of the functional groups, the positive electrode 130 may swell excessively in water and the mechanical properties may deteriorate. On the other hand, when the equivalent weight of the functional groups is higher than 1100 g / mol, due to the low content of the functional groups, the ion exchange capacity of the positive electrode 130 may deteriorate.

[0168] Compared with fluorinated solid electrolytes, hydrocarbon solid electrolytes can be based on compounds with various molecular structures that are more easily polymerized or copolymerized. Hydrocarbon solid electrolytes include sulfonated polyethylene, sulfonated polypropylene, sulfonated polystyrene, sulfonated polysulfone, sulfonated polybenzimidazole, sulfonated polyphenylene ether, sulfonated polyarylene ether ketone, sulfonated polyether ether ketone, sulfonated polyether ketone, sulfonated polyimide, sulfonated polyetherimide, sulfonated poly(styrene-b-ethylene-r-butadiene-b-styrene) triblock copolymer, etc. that contain sulfonic acid groups.

[0169] The second cation exchange binder can be the same as or different from the cation exchange solid electrolyte contained in the solid electrolyte layer 110 and the first cation exchange binder contained in the negative electrode 120, and preferably it is the same as the cation exchange solid electrolyte and the first cation exchange binder.

[0170] The positive electrode 130 may also contain an anion exchange binder. The main products of the carbon dioxide reduction reaction occurring at the positive electrode 130 are carbon monoxide (CO), ethylene (C2H4), propylene (C3H6), formic acid (HCOOH) / formate, methanol (CH3OH), ethanol (C2H5OH), propanol (C3H7OH), etc., and most of the by-products are hydrogen (H2). Hydrogen can be used as a high-value raw material in the conventional petroleum refining industry, fertilizer industry, metal production industry, and food industry. Therefore, its utilization value may be high only when it can be effectively separated and stored after the carbon dioxide reduction reaction, depending on market conditions. To effectively store hydrogen, a high-pressure hydrogen storage system that can withstand a pressure of about 1 MPa to 7 MPa (or 10 bar to 70 bar) should be provided outside the electrochemical cell 10.

[0171] Anion exchange binders include: polystyrene tetramethylimidazolium chloride that contains polystyrene (PS) as the main chain and contains an imidazolium group, a benzimidazolium group binder represented by the following formula 3, a poly(arylpiperidinium) group binder represented by the following formula 4, etc. Alternatively, the anion exchange binder may include commercially available Sustainion TM , Aemion TM , PiperION TM , etc.

[0172] [Formula 3]

[0173]

[0174] Among them, n can be from 10 to 1000.

[0175] [Formula 4]

[0176]

[0177] Among them, x can be from 10 to 1000, and y can be from 10 to 1000.

[0178] Meanwhile, the operating conditions of the electrochemical cell 10 for carbon dioxide conversion may greatly affect the selectivity of the products. An acidic atmosphere with a low pH value can promote the production of formic acid and hydrogen, while an alkaline atmosphere with a high pH value can promote the production of formate and inhibit the production of hydrogen. Therefore, when an acidic atmosphere is required, the second cation exchange binder can be used alone or the content of the second cation exchange binder in the blend of the second cation exchange binder and the anion exchange binder can be increased. On the other hand, when an alkaline atmosphere is required, the content of the anion exchange binder in the blend of the second cation exchange binder and the anion exchange binder can be increased. There is no particular limitation on the mixing ratio of the second cation exchange binder and the anion exchange binder, and the second cation exchange binder and the anion exchange binder can be mixed in a ratio of, for example, about 95:5 to 50:50 or about 90:10 to 75:25. Based on the total weight of the second cation exchange binder and the anion exchange binder, when the content of the anion exchange binder is less than 5 wt%, the mixing effect is insufficient and the mixing of the two substances is meaningless; while when the content of the anion exchange binder exceeds 50 wt%, the phase separation between the two substances becomes serious and it is difficult to obtain a homogeneous mixture.

[0179] The positive electrode antioxidant is included in the second cation exchange binder to mitigate or inhibit the chemical degradation of the positive electrode 130, and the positive electrode antioxidant can include a primary antioxidant and / or a secondary antioxidant.

[0180] When using a fluorinated solid electrolyte as the second cation exchange binder, the positive electrode antioxidant can be a cerium antioxidant as the primary antioxidant. The cerium antioxidant can include cerium oxide (or ceria: CeO x ), modified cerium oxide, cerium(III) nitrate hexahydrate: Ce(NO3)3·6H2O, etc. The modified cerium oxide can include cerium-zirconium oxide (CeZrO x) Cerium-manganese oxide (CeMnO x ), gadolinium (Gd)- or samarium (Sm)-doped cerium oxide, etc.

[0181] Cerium antioxidants can be introduced in the form of particles or powders (nanoparticles or nanopowders) with a grain size of several nanometers or dozens of nanometers. However, cerium oxide and modified cerium oxide should be pre-dispersed before being added to the fluorinated solid electrolyte because they are usually stored in an agglomerated state after production. To improve the degree of dispersion and / or distribution, surfactants can be introduced together with the cerium antioxidants, which may reduce the activity of the cerium antioxidants. Therefore, to improve the dispersibility and activity of the cerium antioxidants, the cerium antioxidants can be introduced in the form of being loaded on a carrier. The carrier can include titanium dioxide (TiO2), silica (SiO2), carbon powder, carbon nanotubes (CNT), etc. Based on the total weight of the carrier and the cerium antioxidants, the content of the cerium antioxidants loaded on the carrier can be about 2 wt% to 70 wt% or about 10 wt% to 50 wt%. When the content of the cerium antioxidants is less than 2 wt%, the antioxidant performance may deteriorate due to the excessive content of the carrier compared with the cerium antioxidants. On the other hand, when the content exceeds 70 wt%, the cerium antioxidants are too densely distributed on the carrier, so it is difficult to effectively load and use the cerium antioxidants.

[0182] Based on the total weight of the second cation exchange binder and the antioxidant in the positive electrode 130, the content of the cerium antioxidant can be about 200 ppm to 50000 ppm or about 1000 ppm to 10000 ppm. When the content of the cerium antioxidant is less than 200 ppm, the antioxidant performance will be greatly reduced; while when the content exceeds 50000 ppm, it is difficult for the cerium antioxidant to be uniformly dispersed in the positive electrode 130, and the ionic conductivity and other physical properties of the positive electrode 130 will decrease and the cost will also increase.

[0183] In the cerium antioxidants, cerium oxide and modified cerium oxide can have a grain size of about 2 nm to 100 nm or about 10 nm to 50 nm measured by X-ray. When the grain size is less than 2 nm, the cerium antioxidant particles may agglomerate during the operation of the battery cell, the activity of the cerium antioxidants may decrease over time, and the long-term durability of the cerium antioxidants may decrease. On the other hand, when the grain size exceeds 100 nm, the initial activity of the cerium antioxidants may be too low.

[0184] When a fluorinated solid electrolyte is used as the second cation-exchange binder, the positive electrode antioxidant can be a manganese antioxidant such as manganese oxide as a secondary antioxidant, a non-manganese transition metal antioxidant such as platinum (Pt), gold (Au), or palladium (Pd), or a combination thereof.

[0185] To increase the dispersibility and activity of the secondary antioxidant, the secondary antioxidant can be loaded on a carrier. The carrier is as described above. Here, the content of the secondary antioxidant loaded on the carrier and the content of the secondary antioxidant based on the total weight of the second cation-exchange binder and the antioxidant in the positive electrode 130 are as described for the cerium antioxidant.

[0186] When a hydrocarbon solid electrolyte is used as the second cation-exchange binder, the positive electrode antioxidant can be a sterically hindered phenolic antioxidant as a primary antioxidant. Specifically, the sterically hindered phenolic antioxidant can include Irganox 1010 containing pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) TM 、Irganox 1076 containing octadecyl-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) TM 、Irganox 245 containing ethylene bis(oxyethylene) bis-(3-(5-tert-butyl-4-hydroxy-m-tolyl)propionate) TM and so on.

[0187] Based on the total weight of the second cation-exchange binder and the antioxidant in the positive electrode 130, the content of the sterically hindered phenolic antioxidant can be about 200 ppm to 50,000 ppm or about 1000 ppm to 10,000 ppm. When the content of the sterically hindered phenolic antioxidant is less than 200 ppm, the antioxidant performance will be greatly reduced; while when the content of the sterically hindered phenolic antioxidant exceeds 50,000 ppm, it is difficult for the phenolic antioxidant to be uniformly dispersed, the ionic conductivity and overall physical properties of the positive electrode 130 will decline and the cost will also increase.

[0188] When a hydrocarbon solid electrolyte is used as the second cation-exchange binder, the positive electrode antioxidant can be a phosphite antioxidant as a secondary antioxidant. The phosphite antioxidant can include Irgafos 168 containing tris(2,4-di-tert-butylphenyl) phosphite TM . Here, based on the total weight of the second cation-exchange binder and the antioxidant in the positive electrode 130, the content of the phosphite antioxidant is as described for the phenolic antioxidant.

[0189] Based on the total weight of the positive electrode 130, the content of the second cation exchange binder can be about 10 wt% to 70 wt% or about 20 wt% to 50 wt%. When the content of the second cation exchange binder is less than 10 wt%, the binding of the positive electrode catalyst is insufficient, and the positive electrode 130 will be delaminated, and the performance of effectively transporting the cations received from the solid electrolyte layer 110 to the positive electrode catalyst may deteriorate. On the other hand, when the content exceeds 70 wt%, the resistance within the positive electrode 130 will increase, and the pores will become too small, resulting in an increase in the mass transfer resistance within the positive electrode 130.

[0190] The thickness of the positive electrode 130 can be about 2 μm to 50 μm or about 3 μm to 30 μm. When the thickness of the positive electrode 130 is less than 2 μm, it may be difficult to uniformly coat the positive electrode 130 on the solid electrolyte layer 110 due to its too small thickness; while when the thickness of the positive electrode 130 exceeds 50 μm, the cell resistance may increase and the performance may decline due to its too large thickness.

[0191] The method for manufacturing the electrode-solid electrolyte assembly 100 is not particularly limited. For example, the decal transfer method, the direct coating method, the spraying method, etc. can be used to produce the electrode-solid electrolyte assembly 100. From the perspective of mass production and quality stability, it is preferable to use the decal transfer method to manufacture the electrode-solid electrolyte assembly 100.

[0192] The decal transfer method is briefly described below. An electrode slurry or a catalyst slurry containing a catalyst, a catalyst carrier, a binder, a mixed solvent such as water and / or alcohol, etc. is applied on a decal transfer film and dried at a temperature below about 90 °C. High-temperature annealing is carried out at about 90 °C to 240 °C or about 100 °C to 130 °C to stabilize the structure of the dried electrode on the decal transfer film and increase the hydrophobicity. When the heat treatment temperature is lower than 90 °C, the effect of the heat treatment may be insufficient; while when the heat treatment temperature exceeds 240 °C, the binder in the electrode may undergo thermal degradation. After completing the high-temperature heat treatment, the electrode is pressed onto the solid electrolyte layer 110 at about 110 °C to 240 °C or about 130 °C to 180 °C using the hot-pressing method to transfer the negative electrode 120 and / or the positive electrode 130 onto the solid electrolyte layer 110. When the high-temperature pressing is carried out at a temperature lower than 110 °C, the decal transfer may be insufficient; while when the high-temperature pressing is carried out at a temperature higher than 240 °C, the binder in the solid electrolyte layer 110 and the electrode may undergo thermal degradation.

[0193] The electrochemical cell 10 for carbon dioxide conversion according to the present invention may include a negative electrode porous transport layer 200 and a positive electrode porous transport layer 300 as independent elements.

[0194] As Figure 4 shown, the negative electrode porous transport layer 200 and the positive electrode porous transport layer 300 are physically in contact with the outer surfaces of the negative electrode 120 and the positive electrode 130, respectively. The negative electrode porous transport layer 200 supplies deionized water as a negative electrode reactant to the negative electrode 120, and transports and discharges both the unreacted deionized water and the by-product oxygen at the negative electrode 120 to the outside of the cell. The positive electrode porous transport layer 300 supplies humidified carbon dioxide as a positive electrode reactant to the positive electrode 130, and transports and discharges both the unreacted carbon dioxide and the product of the positive electrode 130 to the outside of the cell.

[0195] The negative electrode porous transport layer 200 and the positive electrode porous transport layer 300 have different required structures and characteristics according to the operating conditions of their respective electrodes. Due to the high potential operating conditions of the negative electrode 120, the negative electrode porous transport layer 200 is made of an incompressible metal material; while due to the relatively low potential operating conditions of the positive electrode 130, the positive electrode porous transport layer 300 is made of a compressible carbon material.

[0196] Figure 11A An embodiment of the negative electrode porous transport layer 200 according to the present invention is shown. Here, deionized water can be used as the negative electrode reactant, and the negative electrode porous transport layer 200 made of titanium (Ti) or the like with excellent corrosion resistance can be used because it can operate at a high potential above 2V.

[0197] The negative electrode porous transport layer 200 may include a negative electrode macroporous substrate 210 having pores with a diameter of about 1 μm to 300 μm. The mercury intrusion porosimetry method can be used to measure the diameter. When the pore diameter of the negative electrode macroporous substrate 210 is less than 1 μm, it may be difficult to obtain the performance of macropores; while when the pore diameter exceeds 300 μm, it may be difficult for the negative electrode macroporous substrate 210 to be used as a support.

[0198] The negative electrode macroporous substrate 210 may include at least one selected from a titanium fiber felt, a titanium fiber paper, a titanium fiber cloth, a titanium mesh, a titanium foil, and combinations thereof.

[0199] To impart higher corrosion resistance to the negative electrode macroporous substrate 210, as Figures 11B to 11DAs shown, a corrosion-resistant coating 230 can be formed on at least one surface of the negative macroporous substrate 210. The corrosion-resistant coating 230 can be formed by coating at least one of titanium (Ti), iridium (Ir), platinum (Pt), and gold (Au) on the negative macroporous substrate 210 using methods such as sputtering.

[0200] Figure 11E Another embodiment of the negative electrode porous transport layer 200 according to the present invention is shown. In order to reduce the contact resistance between the negative electrode porous transport layer 200 and the negative electrode 120 and to promote the mass transfer of deionized water and oxygen, a negative electrode microporous layer 220 is introduced on the negative macroporous substrate 210. The negative electrode porous transport layer 200 can be laminated on the negative electrode 120 such that the negative electrode microporous layer 220 faces the negative electrode 120.

[0201] The negative electrode microporous layer 220 can include pores with a diameter of less than about 0.2 μm. The diameter can be measured using the mercury intrusion porosimetry method. When the pore diameter of the negative electrode microporous layer 220 is 0.2 μm or more, it may be difficult to uniformly transport deionized water to the negative electrode 120.

[0202] The negative electrode microporous layer 220 can include at least one selected from titanium (Ti), iridium (Ir), platinum (Pt), gold (Au), and combinations thereof.

[0203] The thickness of the negative electrode microporous layer 220 can be about 5 μm to 200 μm or about 10 μm to 50 μm. When the thickness is less than 5 μm, the mass transfer performance may decrease, and the effect of reducing the contact resistance may be insufficient. On the other hand, when the thickness exceeds 200 μm, the mass transfer path may become too long.

[0204] Meanwhile, as Figures 11F to 11H shown, a corrosion-resistant coating 230 can be formed on at least one surface of the negative electrode porous transport layer 200.

[0205] The thickness of the negative electrode porous transport layer 200 can be about 50 μm to 1000 μm or about 100 μm to 600 μm. When the thickness is less than 50 μm, the mechanical stiffness may decrease, and the negative electrode porous transport layer 200 may be damaged during long-term operation of the battery cell. On the other hand, when the thickness exceeds 1000 μm, the mass transfer path may become too long.

[0206] The thickness of the corrosion-resistant coating 230 can be about 10 nm to 400 nm or about 30 nm to 200 nm. When the thickness is less than 10 nm, the corrosion-resistant effect may be insufficient; while when the thickness exceeds 400 nm, the ohmic resistance of the battery cell may increase, and the manufacturing cost may increase.

[0207] The porosity of the negative electrode porous transport layer 200 can be about 20% to 90% or about 40% to 70%. When the porosity is below 20%, the mass transport performance of the negative electrode porous transport layer 200 may be greatly reduced; while when the porosity exceeds 90%, the mechanical stiffness of the negative electrode porous transport layer 200 may be too low, and the negative electrode porous transport layer 200 may be damaged during long-term operation of the battery cell.

[0208] Figure 12 The positive electrode porous transport layer 300 according to the present invention is shown.

[0209] Considering that the reduction reaction of the positive electrode 130 occurs at a low operating voltage below 0.4V, and the conductivity, cost, and material supply and demand characteristics of the positive electrode porous transport layer 300, different from the negative electrode porous transport layer 200, the positive electrode porous transport layer 300 is preferably a compressible carbon material rather than a metal material.

[0210] Since the positive electrode porous transport layer 300 greatly affects the mass transport performance of the positive electrode 130, it greatly affects the high current density operation related to the battery cell productivity and the selectivity of the carbon dioxide reduction reaction product type. In addition, since the positive electrode porous transport layer 300 greatly affects the occurrence of problems such as salt precipitation depending on the mass transport performance, it may greatly affect the performance, durability, and operating stability of the electrochemical battery cell 10. Compared with conventional saline electrolysis cells, chlor-alkali battery cells, fuel cells, and water electrolysis cells, the electrochemical battery cell 10 according to the present invention has significantly different reaction conditions and operating conditions, and the positive electrode 130 has multiple differences including the presence of humidified carbon dioxide. Therefore, the present invention is characterized by optimizing and designing the structure of the positive electrode porous transport layer 300 to adapt to its unique characteristics.

[0211] The positive electrode porous transport layer 300 can include a positive electrode macroporous substrate 310 and a microporous layer 320. The positive electrode macroporous substrate 310 includes pores with a diameter of about 1μm to 300μm, and the microporous layer 320 is disposed on the positive electrode macroporous substrate 310 and includes pores with a diameter less than about 0.2μm. The positive electrode porous transport layer 300 can be laminated on the positive electrode 130 such that the positive electrode microporous layer 320 faces the positive electrode 130. By interposing the positive electrode microporous layer 320 between the positive electrode macroporous substrate 310 and the positive electrode 130, the problem that the carbon fibers of the positive electrode macroporous substrate 310 puncture the positive electrode 130 and the solid electrolyte layer 110 can be solved, and humidified carbon dioxide and products can be transported more effectively.

[0212] When the pore size of the positive macroporous substrate 310 is less than 1 μm, it may be difficult to obtain the performance of macropores; while when the pore size of the positive macroporous substrate 310 exceeds 300 μm, it may be difficult for the positive macroporous substrate 310 to be used as a support. When the pore size of the positive microporous layer 320 is 0.2 μm or more, humidified carbon dioxide may not be evenly delivered to the positive electrode 130. The pore size can be measured using the mercury intrusion porosimetry method.

[0213] The positive macroporous substrate 310 may include at least one selected from carbon fiber felt, carbon fiber paper, carbon fiber cloth, and combinations thereof. In addition, the positive macroporous substrate 310 may also contain a hydrophobic agent.

[0214] The positive microporous layer 320 may include at least one selected from carbon blacks such as acetylene black, black pearl carbon, Ketjen black carbon, Vulcan XC-72 carbon, graphene nanoplatelets, carbon nanotubes, carbon nanofibers, and combinations thereof. In addition, the positive microporous layer 320 may also contain a hydrophobic agent.

[0215] The hydrophobic agent can function to impart hydrophobicity or water repellency.

[0216] The hydrophobic agent may be a fluorinated homopolymer such as polytetrafluoroethylene (PTFE), a fluorinated copolymer such as FKM / FFKM, fluorinated ethylene-propylene copolymer (FEP), or a combination thereof.

[0217] The content of the hydrophobic agent in the positive macroporous substrate 310 may be about 2 wt% to 50 wt% or about 5 wt% to 30 wt%. When the content of the hydrophobic agent in the positive macroporous substrate 310 is less than 2 wt%, the hydrophobicity may be insufficient; while when the content exceeds 50 wt%, the resistance may increase significantly, the porosity may decrease, and thus the cell performance may deteriorate. In addition, to further increase the hydrophobicity of the positive macroporous substrate 310, the positive macroporous substrate 310 can be plasma-modified to increase the surface roughness.

[0218] The content of the hydrophobic agent in the positive microporous layer 320 may be 10 wt% to 60 wt% or 15 wt% to 40 wt%. When the content of the hydrophobic agent in the positive microporous layer 320 is less than 10 wt%, the hydrophobicity may be insufficient; while when the content exceeds 60 wt%, the resistance may increase significantly, the porosity may decrease, and thus the cell performance may decline. In addition, to further increase the hydrophobicity of the positive microporous layer 320, the positive microporous layer 320 can be plasma-modified to increase the surface roughness.

[0219] Considering the efficient discharge of water from the electrochemical cell 10, the content of the water repellent in the cathode microporous layer 320 facing the cathode 130 is higher than that in the cathode macroporous substrate 310, and more preferably at least twice that of the water repellent in the cathode macroporous substrate 310.

[0220] The total thickness of the cathode porous transport layer 300 can be about 50 μm to 1000 μm or about 100 μm to 600 μm. When the thickness is less than 50 μm, the mechanical stiffness may be too low; when the thickness exceeds 1000 μm, the mass transfer path may be too long.

[0221] The porosity of the cathode porous transport layer 300 can be about 50% to 95% or about 60% to 85%. When the porosity is below 50%, the mass transfer performance of the cathode porous transport layer 300 will be greatly reduced; when the porosity exceeds 95%, due to the too low mechanical stiffness of the cathode porous transport layer 300, the cathode porous transport layer 300 may be damaged when the cell including it operates for a long time.

[0222] When pressure is applied to it, the cathode porous transport layer 300 is compressible, and the degree of compressibility is calculated as follows:

[0223] Degree of compressibility = [(t1 - t2) / t1]×100 [%]

[0224] Wherein, t1 is the thickness of the cathode porous transport layer 300 measured when a compressive pressure of 50 kPa is applied to it, and t2 is the thickness of the cathode porous transport layer 300 measured when a compressive pressure of 1 MPa is applied to it. The degree of compressibility of the cathode porous transport layer 300 can be about 2% to 50% or about 5% to 35%. When the degree of compressibility is less than 2%, the cathode porous transport layer 300 exhibits basically incompressible behavior and becomes too stiff, so the handling performance will be reduced when assembling the cell by compression; when the degree of compressibility exceeds 50%, the cathode porous transport layer 300 is too flexible (soft), so the following problems are aggravated: the long-term durability of the cathode porous transport layer 300 is reduced when assembling the cell by compression, and the cathode porous transport layer 300 may intrude into the flow channels of the cathode bipolar plate 600.

[0225] When a compressive pressure of 1 MPa is applied to it, the resistance of the cathode porous transport layer 300 can be about 20 mΩ·cm 2 or less or about 10 mΩ·cm 2 or less. This is because when the resistance exceeds 20 mΩ·cm 2 the performance loss of the cell may increase significantly.

[0226] When the product of the positive electrode 130 is a low-pressure gas or liquid of less than 1 MPa (10 bar), it is preferred that the positive electrode porous transport layer 300 be a rolled product that is very suitable for large-scale production and has excellent handling properties. When the product is a high-pressure gas of higher than 1 MPa (10 bar), the positive electrode porous transport layer 300 can be a rolled product or a sheet product.

[0227] When the bending stiffness of the positive electrode porous transport layer 300 is insufficient, the positive electrode porous transport layer 300 may be damaged during the long-term operation of the battery cell including the positive electrode porous transport layer 300. Therefore, the positive electrode porous transport layer 300 needs to exhibit a sufficiently high bending stiffness.

[0228] The bending stiffness of the positive electrode porous transport layer 300 can be quantified by measuring the Taber bending stiffness (TBS) or the three-point flexural modulus. For example, the Taber bending stiffness of the positive electrode porous transport layer 300 measured using a Taber bending stiffness tester can be about 2 g f ·cm or more, more preferably about 4 g f ·cm or more.

[0229] The positive electrode macroporous substrate 310 can include carbon fibers, so its in-plane mechanical stiffness can be anisotropic depending on its manufacturing method. Specifically, in a rolled product, the mechanical stiffness in the machine direction (MD) as the rolling direction (the positive electrode porous transport layer 300 is wound around a roll in the rolling direction) is generally greater than that in the cross-machine direction or the transverse direction (CMD or TD). The degree of anisotropy of the Taber bending stiffness represents the difference between the bending stiffness of the positive electrode porous transport layer 300 in the high bending stiffness direction (HBSD) and the bending stiffness in the low bending stiffness direction (LBSD), and is calculated as follows:

[0230] Degree of anisotropy of Taber bending stiffness = [(TBS1 - TBS2) / TBS1] × 100 [%]

[0231] where TBS1 is the Taber bending stiffness of the positive electrode porous transport layer 300 in the high bending stiffness direction, and TBS2 is the Taber bending stiffness of the positive electrode porous transport layer 300 in the low bending stiffness direction.

[0232] As Figure 13As shown, when the degree of anisotropy of the bending stiffness of the positive electrode porous transport layer 300 is 30% or more, in order to suppress the problem that the positive electrode porous transport layer 300 intrudes into the positive electrode flow channel 630 of the positive electrode bipolar plate 600, the direction of the positive electrode flow channel (main flow channel) with the longest total length in the positive electrode flow channel 630 is arranged in a non-parallel mode with the high bending stiffness direction of the positive electrode porous transport layer 300. For example, they are perpendicular to each other at 90°. When the degree of anisotropy of the bending stiffness of the positive electrode porous transport layer 300 is less than 30%, the effect of suppressing the intrusion problem by arranging the high bending stiffness direction of the positive electrode porous transport layer 300 and the main flow channel direction of the positive electrode flow channel 630 in a non-parallel structure may be insufficient. In Figure 13 it, another positive electrode flow channel direction with a total length shorter than the direction of the positive electrode flow channel (main flow channel) with the longest total length in the positive electrode flow channel 630 is shown as the secondary flow channel direction.

[0233] The positive electrode porous transport layer 300 has high water resistance or hydrophobicity, and thus has high mass transport performance. The positive electrode porous transport layer 300 has a large water droplet contact angle (CA), a small sliding angle (SA), and a small contact angle hysteresis (CAH) on its surface measured by a sessile droplet test. The contact angle hysteresis is calculated as follows.

[0234] Contact angle hysteresis = Advancing Contact Angle (ACA) - Receding Contact Angle (RCA)

[0235] The contact angle of the positive electrode macroporous substrate 310 is about 120° or more, more preferably about 130° or more, the sliding angle is about 60° or less, more preferably about 30° or less, and the contact angle hysteresis is about 30° or less, more preferably about 20° or less.

[0236] The thickness of the positive electrode microporous layer 320 can be about 5 μm to 250 μm, or about 10 μm to 70 μm. When the thickness is less than 5 μm, the effects of increasing mass transport and reducing contact resistance are insufficient, while when the thickness exceeds 250 μm, the mass transport path may become longer.

[0237] The contact angle of the positive electrode microporous layer 320 is about 130° or more, more preferably about 140° or more, the sliding angle is about 50° or less, more preferably about 25° or less, and the contact angle hysteresis is about 25° or less, more preferably about 15° or less.

[0238] In order to increase the waterproof performance based on an increase in capillary force, the positive electrode microporous layer 320 may have a pore size gradient such that the portion of the positive electrode microporous layer 320 in contact with the positive electrode has the smallest pore size, and the pore size gradually increases toward the portion of the positive electrode microporous layer 320 in contact with the macroporous substrate.

[0239] Depending on the operating conditions of the battery cell and the water content in the battery cell, cracks present on one surface of the positive electrode microporous layer 320 (which is on the positive electrode 130) may affect the battery cell performance and durability. When the solid electrolyte layer 110 becomes wet due to using deionized water as the negative electrode reactant and humidified carbon dioxide gas as the positive electrode reactant, as the reduction reaction of carbon dioxide proceeds for a long time at the positive electrode 130, the residual moisture in the positive electrode 130 increases, resulting in an overflow problem. When macro-cracks larger than a predetermined size are present on one surface of the positive electrode microporous layer 320, the delay or interruption of carbon dioxide supply caused by water overflow can be minimized. Based on a surface area of 5 mm × 5 mm, the length of the macro-cracks present on one surface of the positive electrode microporous layer 320 can be about 100 μm or more or about 300 μm or more. When the length of the macro-cracks is less than 100 μm, the drainage effect may be insufficient. In addition, based on a surface area of 5 mm × 5 mm and the length defined above, there may be at least 10 macro-cracks. When the number of macro-cracks is less than 10, the drainage effect may be insufficient.

[0240] The present invention is characterized in that an interfacial layer 800 containing an anion exchange polymer is integrated with the surface of the positive electrode porous transport layer 300 to inhibit the evolution of hydrogen, a by-product of the side reaction, at the positive electrode 130.

[0241] Since the interfacial layer 800 contains an anion exchange polymer, the positive electrode catalyst in the positive electrode 130 provided on the positive electrode porous transport layer 300 can be kept alkaline, thereby inhibiting the hydrogen evolution reaction from occurring at the positive electrode 130.

[0242] The anion exchange polymer includes polystyrene tetramethyl imidazolium chloride containing polystyrene (PS) as the main chain and containing an imidazolium group, a benzimidazolium-based polymer represented by the following formula 5, a poly(aryl piperidinium)-based polymer represented by the following formula 6, etc. Alternatively, the anion exchange polymer may include commercially available Sustainion TM 、AemionTM , PiperION TM and so on.

[0243] [Formula 5]

[0244]

[0245] Among them, n can be from 10 to 1000.

[0246] [Formula 6]

[0247]

[0248] Among them, x can be from 10 to 1000, and y can be from 10 to 1000.

[0249] The interface layer 800 can be integrated with the positive electrode porous transport layer 300. There is no particular limitation on the integration method of the interface layer 800. For example, the interface layer 800 can be integrated into the positive electrode porous transport layer 300 by directly coating, spray-coating, or spin-coating the positive electrode porous transport layer 300 with a dispersion prepared by dissolving an anion exchange polymer in a solvent.

[0250] The thickness of the interface layer 800 can be about 20 nm to 3 μm or about 100 nm to 1 μm. When the thickness of the interface layer 800 is less than 20 nm, it may be difficult to impart alkalinity to the positive electrode catalyst in contact with the interface layer 800. On the other hand, when the thickness of the interface layer 800 exceeds 3 μm, the resistance of the positive electrode porous transport layer 300 increases, the pores of the positive electrode microporous layer 320 may be clogged, and the mass transfer performance may deteriorate.

[0251] In a preferred example of the electrochemical cell 10 according to the present invention, the positive electrode 130 contains a second cation exchange binder and an anion exchange binder, and the interface layer 800 containing an anion exchange polymer integrated with the positive electrode porous transport layer 300 can contact the positive electrode 130. The electrochemical cell 10 can effectively inhibit the hydrogen evolution reaction occurring at the positive electrode 130.

[0252] Figure 14 The negative electrode bipolar plate 400 according to the present invention is shown. The negative electrode bipolar plate 400 can include a first negative electrode manifold 410 penetrating the negative electrode bipolar plate 400 at a predetermined position, a second negative electrode manifold 420 penetrating the negative electrode bipolar plate 400 at a position separated from the first negative electrode manifold 410 by a predetermined distance, and a negative electrode flow channel 430 recessed from one surface of the negative electrode porous transport layer 200 into the negative electrode bipolar plate 400 to connect the first negative electrode manifold 410 to the second negative electrode manifold 420.

[0253] Such as Figure 14As shown, when dozens to hundreds of battery cells are assembled into a battery cell stack, a manifold is required to effectively supply, recycle, and discharge various reactants and products. Each negative bipolar plate 400 requires a pair of reactant manifolds and a pair of product manifolds, and whether there is a pair of coolant manifolds can be determined according to the target performance of the battery cell and the system configuration. For example, when sufficient cooling is required for a multi-cell stack with a large active area for electrochemical reaction of more than 200 cm 2 and a high power of more than 50 kW, a coolant manifold can be used to supply and recycle the coolant. Figure 14 An example is shown in which each bipolar plate has a pair of reactant manifolds, a pair of product manifolds, and a pair of coolant manifolds.

[0254] The negative flow channel 430 can have a serpentine structure, a parallel structure, an interdigitated structure, a mesh structure, or a foam structure. Figure 14 The serpentine structure of the negative flow channel 430 is shown. The negative flow channel 430 can include a main flow channel 431 with the longest total length and a secondary flow channel 432 with a smaller total length.

[0255] Figure 15 is a cross-sectional view showing the negative bipolar plate 400 according to the present invention. Since deionized water is used as the negative reactant and the battery cell operates at a high voltage of more than 2 V, the negative bipolar plate 400 can have a double-layer structure, which includes a negative bipolar plate base 440 made of a metal with excellent corrosion resistance such as titanium (Ti) or stainless steel (SS), and a negative bipolar plate coating 450 provided on its surface to increase corrosion resistance and reduce contact resistance.

[0256] The stainless steel constituting the negative bipolar plate base 440 exhibits excellent corrosion resistance due to its high chromium (Cr) content, and it can include 446 as ferritic SS (stainless steel), 304, 316, or 316L as austenitic SS, or 410 or 440A as martensitic SS. The Cr content of the ferritic SS can be about 20 wt% to 40 wt%. When the Cr content is less than 20 wt%, the corrosion resistance deteriorates; while when the Cr content exceeds 40 wt%, it may be difficult to maintain the balance between all physical properties.

[0257] The negative bipolar plate coating 450 can be formed as a single layer or a double layer. As Figure 15As shown, a single negative bipolar plate coating 450 can be formed by coating with titanium (Ti), iridium (Ir), platinum (Pt), gold (Au), niobium (Nb), tantalum (Ta), or a combination thereof. Methods such as magnetron sputtering and physical vapor deposition can be used to form the single negative bipolar plate coating 450. Under the high-potential operating conditions of the negative electrode 120, the thickness of the single negative bipolar plate coating 450 can be about 0.1 μm to 20 μm or about 0.5 μm to 5 μm. This is because when the thickness is less than 0.1 μm, the effects of increasing corrosion resistance and reducing contact resistance may be insufficient; while when the thickness exceeds 20 μm, the cost of manufacturing the coating will increase significantly.

[0258] Meanwhile, when the negative bipolar plate coating 450 is formed as a double-layer structure, one surface of the negative bipolar plate substrate 440 is first coated with titanium (Ti) to form a first coating, and then coated with Ti, Ir, Pt, Au, Nb, Ta, or a combination thereof to form a second coating to further increase corrosion resistance and reduce contact resistance. At this time, a Ti coating as the first coating can be formed by thermal spraying, and another coating containing Ti, Ir, Pt, Au, Nb, Ta, etc. as the second coating can be formed by magnetron sputtering, physical vapor deposition, etc. The thickness of the double-layer negative bipolar plate coating 450 can be about 0.1 μm to 20 μm or about 0.5 μm to 5 μm. When the thickness is less than 0.1 μm, the effects of increasing corrosion resistance and reducing contact resistance may be insufficient; while when the thickness exceeds 20 μm, the cost of manufacturing the coating will increase significantly.

[0259] Figure 16 A negative electrode gasket 500 according to the present invention is shown. Figure 17 A combination of the negative electrode gasket 500 and the negative bipolar plate 400 according to the present invention is shown. The negative electrode gasket 500 will be described later.

[0260] Figure 18 A positive bipolar plate 600 according to the present invention is shown. The positive bipolar plate 600 can include a first positive manifold 610 that penetrates the positive bipolar plate 600 at a predetermined position, a second positive manifold 620 that penetrates the positive bipolar plate 600 at a position spaced a predetermined distance from the first positive manifold 610, and a positive flow channel 630 that recesses from one surface of the positive porous transport layer 300 into the positive bipolar plate 600 to connect the first positive manifold 610 to the second positive manifold 620.

[0261] As Figure 18As shown, when dozens to hundreds of battery cells are assembled into a battery cell stack, a manifold is required to effectively supply, recycle, and discharge various reactants and products. Each positive bipolar plate 600 requires a pair of reactant manifolds and a pair of product manifolds, and whether there is a pair of coolant manifolds can be determined according to the target performance of the battery cells and the system configuration. For example, when sufficient cooling is required for a multi-cell stack with a large active area for electrochemical reaction of more than 200 cm 2 and a high power of more than 50 kW, coolant manifolds can be used to supply and recycle the coolant. As Figure 18 shown, an example is presented where each bipolar plate has a pair of reactant manifolds, a pair of product manifolds, and a pair of coolant manifolds.

[0262] The positive electrode flow channel 630 can have a serpentine structure, a parallel structure, an interdigitated structure, a mesh structure, or a foam structure. Figure 18 The serpentine structure of the positive electrode flow channel 630 is shown. The positive electrode flow channel 630 can include a main flow channel 631 with the longest total length and secondary flow channels 632 with a smaller total length.

[0263] Figure 19 A cross-sectional view of the positive bipolar plate 600 according to the present invention is shown.

[0264] The positive bipolar plate 600 can have a double-layer structure including a positive bipolar plate substrate 640 and a positive bipolar plate coating 650.

[0265] The positive bipolar plate substrate 640 can contain metal materials such as titanium or stainless steel. Compared with conventional carbon materials, the above materials have more excellent electrical conductivity, material supply and demand, excellent corrosion resistance and formability, and a lower price to eliminate the risk of damage to the positive bipolar plate 600 due to external pressure during mass forming and stack assembly. Stainless steel exhibits excellent corrosion resistance due to its high chromium (Cr) content, and it can include 446 as ferritic SS, 304, 316, or 316L as austenitic SS, or 410 or 440A as martensitic SS. The Cr content of ferritic SS can be 20 wt% to 40 wt%. When the Cr content is less than 20 wt%, the corrosion resistance deteriorates; while when the Cr content exceeds 40 wt%, it may be difficult to maintain the balance between all physical properties.

[0266] The positive bipolar plate coating 650 can be disposed on the surface of the positive bipolar plate substrate 640 to further increase corrosion resistance and reduce contact resistance. The positive bipolar plate coating 650 can be formed by coating titanium (Ti), iridium (Ir), platinum (Pt), gold (Au), niobium (Nb), tantalum (Ta), or a combination thereof. Additionally, the positive bipolar plate coating 650 can be formed by coating carbon or a ceramic material or a combination thereof.

[0267] Under the low-potential operating conditions of the positive electrode 130, the thickness of the positive bipolar plate coating 650 can be about 10 nm to 700 nm or about 50 nm to 200 nm. When the thickness is less than 10 nm, the effects of increasing corrosion resistance and reducing contact resistance may be insufficient; while when the thickness exceeds 700 nm, the manufacturing cost of the positive bipolar plate coating 650 will increase significantly.

[0268] Figure 20 The positive electrode gasket 700 according to the present invention is shown. Figure 21 The combination of the positive electrode gasket 700 and the positive bipolar plate 600 according to the present invention is shown.

[0269] In order to maintain the sealing of reactants and products in an electrochemical cell and / or cell stack for carbon dioxide conversion, generally each cell needs to have a gasket with appropriate compressibility and high elasticity. When the size of the gasket is smaller than the size of the porous transport layer, the surface of the gasket is disposed on the surface of the porous transport layer, and the sealing of the cell cannot be maintained. Therefore, the size of the gasket should be larger than the size of the porous transport layer.

[0270] The negative electrode gasket 500 and the positive electrode gasket 700 are made of a polymer elastomer as a base material, which is prepared by adding additives such as a crosslinking agent, a co-crosslinking agent or a crosslinking promoter, and a filler to the polymer elastomer, and then heating and crosslinking the compound.

[0271] In the related art, a stand-alone structure (free-standing structure) in which the gasket is separately manufactured and further combined with the bipolar plate or an integrated structure in which the gasket is combined with the solid electrolyte is used. In particular, for the efficient large-scale production of a cell stack with a high power of more than 50 kW based on a large active area cell with an active area of more than 200 cm 2 above, the components of each cell and the cell stack must be quickly assembled and stacked. However, in terms of the handling performance of the cell components required for manufacturing such a cell stack, the conventional stand-alone structure is not suitable. Additionally, in terms of the thermal resistance required during the high-temperature crosslinking of the gasket, the integrated structure in which the gasket is bonded to the solid electrolyte is also not suitable.

[0272] Therefore, to solve these conventional problems, the present invention provides an integrated structure, as Figure 17 and Figure 21 shown, in which the negative electrode gasket 500 and the positive electrode gasket 700 are respectively over-molded on the negative bipolar plate 400 and the positive bipolar plate 600 with excellent heat resistance performance by injection molding.

[0273] The performance and long-term durability of the negative electrode gasket 500 and the positive electrode gasket 700 are closely related to various physical properties such as compression degree, hardness, and compression set. In addition, in order to efficiently injection mold the negative electrode gasket 500 and the positive electrode gasket 700, the compound needs to have high processability or fluidity.

[0274] In the present invention, the compound is injection molded on the negative bipolar plate 400 and the positive bipolar plate 600 in an injection molding machine, and then crosslinked once to form an integrated structure, and then the integrated structure is taken out of the mold in the injection molding machine. Then, the structure is sufficiently post-crosslinked or post-cured (post-curing) in a dedicated crosslinking chamber. In particular, when the crosslinking speed is too high during the first crosslinking, pre-curing or scorch problems may occur, resulting in the inability to form the negative electrode gasket 500 and the positive electrode gasket 700. On the other hand, when the crosslinking speed is too low, it is disadvantageous that the gasket production cycle increases and the productivity decreases. Therefore, it is very important to precisely control the composition, injection molding time, and temperature of the compound to ensure an appropriate crosslinking speed.

[0275] When an external pressure is applied thereto, the negative electrode gasket 500 and the positive electrode gasket 700 are compressible within an appropriate range, and the compression degree is calculated as follows:

[0276] Compression degree = [(t1 - t2) / t1] × 100 [%]

[0277] wherein, t1 is the thickness of the negative electrode gasket 500 or the positive electrode gasket 700 measured when a compression pressure of 50 kPa is applied thereto, and t2 is the thickness of the negative electrode gasket 500 or the positive electrode gasket 700 measured when a compression pressure of 1 MPa is applied thereto. The compression degree of the negative electrode gasket 500 or the positive electrode gasket 700 can be about 2% to 40% or about 5% to 25%. When the compression degree is less than 2%, the negative electrode gasket 500 or the positive electrode gasket 700 will become too rigid, so it becomes difficult to obtain close contact and sealing of the battery cells in the battery cell stack when dozens to hundreds of battery cells are assembled into the battery cell stack; while when the compression degree exceeds 40%, the negative electrode gasket 500 or the positive electrode gasket 700 is too flexible (soft), so when the battery cell is compressed, due to the excessive compression of the negative electrode gasket 500 or the positive electrode gasket 700, the long-term sealing performance and durability deteriorate.

[0278] The hardness of the negative electrode gasket 500 and the positive electrode gasket 700 should be maintained within an appropriate range because they are closely related to compressibility, elasticity, mechanical properties, crosslink density, and chemical resistance. The negative electrode gasket 500 and the positive electrode gasket 700 may have a Shore A hardness of about 30 to 90 or about 50 to 85 measured according to ASTM (American Society for Testing and Materials) D2240. When the Shore A hardness is less than 30, the negative electrode gasket 500 and the positive electrode gasket 700 may be over-compressed when the battery cell is pressurized, which may reduce the long-term sealing performance and durability; while when the Shore A hardness exceeds 90, it may be difficult to obtain tight contact and sealing of the battery cells in the battery cell stack.

[0279] The compression set of the negative electrode gasket 500 and the positive electrode gasket 700 is closely related to elasticity and crosslink density. As the compression set decreases, the elasticity of the negative electrode gasket 500 and the positive electrode gasket 700 increases. When measured under the conditions of ASTM D395 (Method B, 25% deflection, 100 °C / 72 hours), the compression set of the negative electrode gasket 500 and the positive electrode gasket 700 can be about 15% or less or about 10% or less.

[0280] The Mooney Viscosity of the compound is an indicator of the moldability and fluidity of the negative electrode gasket 500 and the positive electrode gasket 700, which is inversely proportional to the injection moldability and is preferably maintained within a predetermined range. When measured under the conditions of ISO289-1 (2005) (ML(1+4) / 125 °C), the Mooney Viscosity of the compound can be about 5 to 40 or about 10 to 30. When the Mooney Viscosity is less than 5, the overall physical properties of the negative electrode gasket 500 and the positive electrode gasket 700, such as elasticity, mechanical properties, and handling properties, may be greatly reduced; while when the Mooney Viscosity exceeds 40, the injection moldability may decrease and the productivity may be reduced.

[0281] It is very important to select the materials for the negative electrode gasket 500 and the positive electrode gasket 700 because the negative electrode gasket 500 and the positive electrode gasket 700 require various physical properties and requirements, such as compressibility, elasticity, mechanical properties, chemical resistance, long-term durability, moldability, and cost.

[0282] For the negative electrode gasket 500 and the positive electrode gasket 700, fluorine-containing elastomers, hydrocarbon elastomers, or silicone elastomers can be used alone or in combination.

[0283] Fluorine-containing elastomers have excellent elasticity, chemical resistance, heat resistance, etc. Due to the low polarizability and strong electronegativity of fluorine atoms, fluorine-containing elastomers exhibit unique properties. Fluorine-containing elastomers with a high fluorine content have excellent thermal stability, chemical stability, anti-aging, weather resistance, and chemical resistance. In addition, fluorine-containing elastomers exhibit characteristics such as low dielectric constant, low flammability, low surface energy, and hygroscopicity. The C-F bond in fluorine-containing elastomers contributes greatly to their high antioxidant and hydrolysis resistance. According to ASTM standards, fluorine-containing elastomers can be roughly classified into FKM, FFKM, etc. Fluorine-containing elastomers include fluorine-containing elastomers synthesized by copolymerization of monomers or combinations thereof, such as vinylidene fluoride (VDF), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and perfluoroalkyl vinyl ether (PAVE).

[0284] Hydrocarbon elastomers have the advantages of low cost, excellent low-temperature flexibility, and high chemical resistance. Hydrocarbon elastomers can include copolymerized hydrocarbon elastomers, such as EPDM (ethylene-propylene-diene monomer) or EPR (ethylene-propylene rubber), or combinations thereof. As a terpolymer monomer, in addition to ethylene and propylene, EPDM also includes ethylidene norbornene (ENB), dicyclopentadiene (DCPD), and 1,4-hexadiene (HD), preferably including ethylidene norbornene.

[0285] Silicone elastomers have low acid resistance but have high-precision injection moldability suitable for gaskets and excellent physical properties. Silicone elastomers can include general silicone elastomers such as polydimethylsiloxane (PDMS), modified silicone elastomers such as acid-resistant enhanced fluorosilicone, or combinations thereof. Solid silicone elastomers can be used, but for precision injection molding, liquid silicone is preferably used.

[0286] Figure 22 Fig. 1000 shows a cell stack 1000 according to the present invention. The cell stack 1000 may include a stack in which a plurality of electrochemical cells 10 are stacked and end plates 20 provided on two surfaces of the stack.

[0287] Figure 23 Fig. 20 shows an end plate 20 according to the present invention. Figure 24 Fig. shows along Figure 23 The cross-sectional view taken along the C-C' line.

[0288] The end plate 20 can be of the penetrating type or the non-penetrating type. The penetrating end plate has a structure for forming manifolds for reactants, products, and coolants on the non-penetrating end plate, and mass transfer of reactants, products, and coolants is carried out through the manifold 21.

[0289] The end plate 20 supports the various components within the cell stack 1000, and while fixing the cell stack 1000, maintains a uniform compression pressure to suppress an increase in contact resistance within the cell stack 1000. For this purpose, the end plate 20 should have various functions such as high mechanical strength, chemical resistance, hydrolysis resistance, lightness, insulation, flame retardancy, and mass producibility. Although the end plate is very important, in the art, machined heavy metal materials lacking physical properties such as corrosion resistance are usually used, or special polymer plastic materials with very low mechanical properties compared to metal materials are used. Therefore, the present invention provides a novel multi-functional end plate to solve these problems existing in the prior art.

[0290] Conventional end plates are usually made only of machined metal materials such as stainless steel. In this case, the end plate may be corroded by reactants, products, and coolants used in the electrochemical reaction. In addition, metal corrosion products such as various metal cations are generated and eluted, resulting in poisoning and contamination of internal components such as the solid electrolyte of the cell and the binder in the electrode. In addition, the metal material may cause problems such as an increase in the weight of the end plate, a reduction in production speed due to machining, and an increase in manufacturing cost.

[0291] Alternatively, conventional end plates are formed only of polymer materials. The end plate made of polymer materials is light in weight and has excellent insulation properties, and is suitable for mass production using injection molding. However, compared with an end plate having the same structure and made of metal materials, the end plate made of polymer materials has disadvantages such as extremely low mechanical strength, a high strain rate, and non-uniform compression pressure applied to the cells in the cell stack.

[0292] The end plate 20 according to the present invention may include a core 23 containing metal and a shell 24 surrounding the core 23 and containing a composite material of polymer and glass fiber. By covering the outer surface of the core 23 with the shell 24 through injection molding, deformation can be minimized by the excellent mechanical strength of the core 23, while maintaining the excellent insulation, chemical resistance, hydrolysis resistance, lightness, and mass producibility of the shell 23.

[0293] The core 23 may include at least one selected from stainless steel, aluminum (Al), and aluminum alloy.

[0294] The housing 24 contains about 50 wt% to 90 wt% of a thermoplastic polymer and about 10 wt% to 50 wt% of glass fibers, or about 60 wt% to 80 wt% of a thermoplastic polymer and about 20 wt% to 40 wt% of glass fibers. When the content of the glass fibers is less than 10 wt%, the effect of enhancing the physical properties by adding the glass fibers is insufficient; while when the content of the glass fibers exceeds 50 wt%, the content of the glass fibers becomes too large, reducing the injection moldability of the housing 24.

[0295] The thermoplastic polymer may include at least one selected from the following polymers suitable for injection molding: polyamide (PA), polyphenylene sulfide (PPS), polyimide (PI), polyetherimide (PEI), polycarbonate (PC), polyphenylene oxide (PPO), polyphenylene ether (PPE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyether ketone (PEK), polyether ether ketone (PEEK), polyether ether ketone ketone (PEEKK), polyethylene (PE), and polypropylene (PP). The thermoplastic polymer may include homopolymers or random, graft, block, or alternating copolymers, or mixtures of polymers with another thermoplastic polymer, thermosetting polymer, rubber, etc. In addition, organic additives and / or inorganic additives may be mixed with the thermoplastic polymer.

[0296] The polyamide may include at least one of aliphatic polyamide, aromatic polyamide, and semi-aromatic polyamide, preferably including semi-aromatic polyamide having excellent heat resistance and injection moldability.

[0297] The end plate 20 can be manufactured by injection molding the housing 24 on the outer surface of the core 23. For example, when the core 23 containing austenitic SS 304 in stainless steel is covered with a composite material of semi-aromatic polyamide and glass fibers, injection molding can be carried out in an injection molding machine at a processing temperature of 310 °C to 370 °C and at a temperature of 60 °C to 170 °C in the injection mold for 1 minute to 60 minutes.

[0298] The housing 24 may also contain a flame retardant. The housing 24 can be produced by adding an appropriate flame retardant together with the thermoplastic polymer, glass fibers, etc. The flame retardant may be in the form of powder or masterbatch pellet. Preferably, the flame retardant is a masterbatch pellet so as to uniformly mix the flame retardant with the thermoplastic polymer and / or glass fibers.

[0299] The flame retardant may include an environmentally friendly non-halogen (halogen-free) flame retardant. Halogenated flame retardants have problems such as releasing toxic gases harmful to humans in the event of a fire.

[0300] The halogen-free flame retardant includes aluminum hydroxide, magnesium hydroxide, calcium hydroxide, ammonium phosphate, ammonium phenyl phosphate, diammonium phosphate, ammonium dimethylphosphate, ammonium ethyl phosphate, melamine phosphate, melamine diphenyl phosphate, melamine pyrophosphate, urea phosphate, expanded graphite, nano clay, or a mixture thereof.

[0301] Based on the total weight of the shell 24, the content of the flame retardant can be about 1 wt% to 40 wt% or about 5 wt% to 30 wt%. When the content of the flame retardant is less than 1 wt%, the flame retardant effect is insufficient; while when the content of the flame retardant exceeds 40 wt%, due to the excessive content of the flame retardant, the dispersibility of the flame retardant will decrease and the inherent physical properties of the shell 24 will also decrease.

[0302] It can be clearly seen from the above that an electrochemical cell for carbon dioxide conversion suitable for large-scale production can be obtained according to the present invention.

[0303] According to the present invention, an electrochemical cell for carbon dioxide conversion can be obtained, which exhibits maximized performance due to its low cell resistance.

[0304] According to the present invention, an electrochemical cell for carbon dioxide conversion can be obtained, which minimizes the overflow problem.

[0305] According to the present invention, an electrochemical cell for carbon dioxide conversion can be obtained, which has a high operating current density.

[0306] According to the present invention, an electrochemical cell for carbon dioxide conversion can be obtained, which is highly durable, thus having a long lifespan and high stability.

[0307] The effects of the present invention are not limited to the above. It should be understood that the effects of the present invention include all effects that can be inferred from the foregoing description of the present invention.

[0308] The present invention has been described in detail with reference to the preferred embodiments of the present invention. However, those skilled in the art should understand that changes can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An electrochemical cell for carbon dioxide conversion, comprising: An electrode-solid electrolyte assembly, said electrode-solid electrolyte assembly comprising: A solid electrolyte layer including a cation-exchange solid electrolyte, A negative electrode coated on one surface of said solid electrolyte layer and integrated with said solid electrolyte layer, wherein said negative electrode includes a negative electrode catalyst and a first cation-exchange binder, and A positive electrode coated on the other surface of said solid electrolyte layer and integrated with said solid electrolyte layer, wherein said positive electrode includes a positive electrode catalyst and a second cation-exchange binder; A negative electrode porous transport layer provided on said negative electrode; A positive electrode porous transport layer provided on said positive electrode; and An interface layer located between said positive electrode and said positive electrode porous transport layer and containing an anion-exchange polymer, Wherein water is supplied to said negative electrode through said negative electrode porous transport layer, wherein an oxidation reaction of water occurs at said negative electrode, and Wherein carbon dioxide is supplied to said positive electrode through said positive electrode porous transport layer, wherein a reduction reaction of carbon dioxide occurs at said positive electrode.

2. The electrochemical cell according to claim 1, wherein at least one product selected from the group consisting of formic acid, ethylene, propylene, alcohols, and combinations thereof is obtained at said positive electrode through the reduction reaction of carbon dioxide.

3. The electrochemical cell according to claim 1, wherein said solid electrolyte layer includes: A central portion in contact with said negative electrode and said positive electrode; And An edge portion other than said central portion, The electrochemical cell further includes a protection member provided on said edge portion, and Said protection member is installed in a region defined by one surface of said edge portion and one side surface of said negative electrode and a region defined by the other surface of said edge portion and one side surface of said positive electrode.

4. The electrochemical cell according to claim 1, wherein said solid electrolyte layer includes: At least one reinforcing layer having a plurality of pores filled with a first cation-exchange solid electrolyte; And An ion-exchange layer provided on at least one surface of said reinforcing layer and including a second cation-exchange solid electrolyte.

5. The electrochemical cell according to claim 1, wherein at least one of said solid electrolyte layer, said negative electrode, and said positive electrode further contains an antioxidant, and Wherein said antioxidant includes at least one selected from the group consisting of cerium antioxidants, manganese antioxidants, non-manganese transition metal antioxidants, phenolic antioxidants, phosphite antioxidants, and combinations thereof.

6. The electrochemical cell according to claim 1, wherein the water supplied to said negative electrode includes deionized water having a specific resistance of about 18 MΩ·cm or more, and Wherein the carbon dioxide supplied to said positive electrode includes humidified carbon dioxide having a relative humidity of about 10% to 90%.

7. The electrochemical cell according to claim 1, wherein said positive electrode further includes an anion-exchange binder.

8. The electrochemical cell according to claim 1, wherein said negative electrode porous transport layer includes a negative electrode macroporous substrate containing pores having a diameter of 1 μm to 300 μm, and The negative macroporous substrate includes at least one selected from the group consisting of titanium fiber felt, titanium fiber paper, titanium fiber cloth, titanium mesh, titanium foil, and combinations thereof.

9. The electrochemical cell according to claim 8, wherein the negative porous transport layer further includes a negative microporous layer disposed on the negative macroporous substrate and including pores having a diameter of less than about 0.2 μm. The negative microporous layer includes at least one selected from the group consisting of titanium (Ti), iridium (Ir), platinum (Pt), gold (Au), and combinations thereof, and the negative porous transport layer is laminated on the negative electrode such that the negative microporous layer faces the negative electrode.

10. The electrochemical cell according to claim 1, wherein the negative porous transport layer includes a corrosion-resistant coating disposed on at least one surface of the negative porous transport layer and including at least one selected from the group consisting of titanium (Ti), iridium (Ir), platinum (Pt), gold (Au), and combinations thereof.

11. The electrochemical cell according to claim 1, wherein the positive porous transport layer includes a positive macroporous substrate having pores with a diameter of about 1 μm to 300 μm, and the positive macroporous substrate includes at least one selected from the group consisting of carbon fiber felt, carbon fiber paper, carbon fiber cloth, and combinations thereof.

12. The electrochemical cell according to claim 11, wherein the positive porous transport layer further includes a positive microporous layer disposed on the positive macroporous substrate and including pores having a diameter of less than about 0.2 μm. The positive microporous layer includes at least one selected from the group consisting of carbon black, graphene nanosheets, carbon nanotubes, carbon nanofibers, and combinations thereof; and the positive porous transport layer is laminated on the positive electrode such that the positive microporous layer faces the positive electrode.

13. The electrochemical cell according to claim 1, wherein the interface layer is integrated with the positive porous transport layer.

14. The electrochemical cell according to claim 1, wherein the thickness of the interface layer is 20 nm to 3 μm.

15. The electrochemical cell according to claim 1, further comprising: a negative bipolar plate disposed on the negative porous transport layer; a negative gasket disposed between the electrode-solid electrolyte assembly and the negative bipolar plate; a positive bipolar plate disposed on the positive porous transport layer; and a positive gasket disposed between the electrode-solid electrolyte assembly and the positive bipolar plate, wherein the negative bipolar plate includes: a first negative manifold penetrating the negative bipolar plate at a predetermined position; a second negative manifold penetrating the negative bipolar plate at a position spaced a predetermined distance from the first negative manifold; and a negative flow channel recessed from a surface of the negative porous transport layer into the negative bipolar plate to connect the first negative manifold to the second negative manifold, and wherein water supplied through the first negative manifold flows through the negative flow channel and is supplied to the negative porous transport layer, wherein the positive bipolar plate includes: a first positive manifold penetrating the positive bipolar plate at a predetermined position; A second positive electrode manifold that penetrates the positive electrode bipolar plate at a position separated from the first positive electrode manifold by a predetermined distance; and A positive electrode flow channel that is recessed from one surface of the positive electrode porous transport layer into the positive electrode bipolar plate, thereby connecting the first positive electrode manifold to the second positive electrode manifold, and wherein carbon dioxide supplied through the first positive electrode manifold flows through the positive electrode flow channel and is supplied to the positive electrode porous transport layer.

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