Electrodes for metal-metal hydride batteries and methods for manufacturing the same

Abstract

An electrode for a metal-hydrogen battery is described. The electrode includes one or more porous layers, each of the porous layers includes a porous substrate and a catalyst layer overlying the porous substrate, the catalyst layer includes a transition metal, and at least one of the at least one porous layer includes a surface having a feature that facilitates hydrogen gas transport. In some embodiments, the anode electrode includes a first porous layer having a first surface and a second porous layer adjacent to the first porous layer having a second surface, the first surface of the first porous layer and the second surface of the second porous layer forming hydrogen gas transport channels.

Description

Technical Field

[0001] <Related Applications> This application claims the priority and benefit of U.S. Patent Application No. 17 / 847,591, filed Jun. 23, 2022, which claims the priority and benefit of U.S. Patent Application No. 63 / 214,514, filed Jun. 24, 2021, and the entire contents of these are incorporated herein by reference.

[0002] The present disclosure generally relates to metal hydride batteries and methods for manufacturing such batteries, and more particularly, to anode electrodes used in metal hydride batteries and methods for manufacturing such anode electrodes.

Background Art

[0003] In order for renewable energy resources such as wind power and sunlight to compete with traditional fossil fuels, large-scale energy storage systems are necessary to mitigate their inherent intermittency. In order to construct large-scale energy storage devices, cost and long-term life are the greatest considerations. Currently, pumped hydroelectric power dominates the grid energy storage market because it is an inexpensive method for storing large amounts of energy over a long period (about 50 years), but it has limitations due to the lack of suitable locations and environmental footprints. Other technologies such as compressed air and flywheel energy storage exhibit several different advantages, but their relatively low efficiency and high cost should be significantly improved for grid storage. Rechargeable batteries offer a great opportunity to target low-cost, high-capacity, and high-reliability systems for large-scale energy storage.

Summary of the Invention

[0004] This specification describes electrodes for metal-hydrogen batteries, as well as methods for fabricating electrodes and batteries. In some embodiments, the electrode for a metal-hydrogen battery comprises one or more porous layers, each porous layer comprising a porous substrate and a catalyst layer covering the porous substrate, the catalyst layer comprising a transition metal, and at least one of the porous layers comprising a surface having features that facilitate hydrogen gas transport. In some embodiments, the anode electrode comprises a first porous layer having a first surface and a second porous layer adjacent to the first porous layer having a second surface, the first surface of the first porous layer and the second surface of the second porous layer forming a transport channel.

[0005] In some embodiments, the anode electrode includes a first porous layer having a first surface and a second porous layer adjacent to the first porous layer having a second surface, wherein the first surface of the first porous layer and the second surface of the second porous layer form transport channels.

[0006] In some embodiments, a battery is presented. The battery comprises a pressure vessel and an electrode stack disposed within the pressure vessel, the electrode stack holding an electrolyte membrane, the electrode stack comprising alternately stacked cathode electrodes and anode electrodes separated by a separator, the anode electrode comprising one or more porous layers, each porous layer comprising a porous substrate and a catalyst layer covering the porous substrate, the catalyst layer comprising a transition metal, and at least one of the porous layers comprising a surface having characteristics that facilitate hydrogen gas transport.

[0007] In some embodiments, a method for forming electrodes for a metal-hydrogen battery includes obtaining one or more porous substrates, forming surface features on at least one surface of at least one porous substrate, coating one or more porous substrates with a catalyst layer to form a porous layer, and connecting the porous layers to form an electrode.

[0008] Other embodiments can be considered and are described below herein. [Brief explanation of the drawing]

[0009] Specific features of various embodiments of this technology are described in detail in the appended claims. A better understanding of the features and advantages of this technology will be obtained by referring to the following detailed description and appended drawings illustrating exemplary embodiments in which the principles of this disclosure are utilized:

[0010] [Figure 1A] A schematic diagram of a metal-hydrogen battery, which may include the electrode embodiments described herein, is shown. [Figure 1B] A schematic diagram of a metal-hydrogen battery, which may include the electrode embodiments described herein, is shown. [Figure 1C] A schematic diagram of a metal-hydrogen battery, which may include the electrode embodiments described herein, is shown.

[0011] [Figure 2] The following are cross-sectional views of electrodes having a single-layer structure according to some embodiments of this disclosure.

[0012] [Figure 3A] Cross-sectional views of electrodes having a double-layer structure according to some embodiments of this disclosure are shown.

[0013] [Figure 3B] Cross-sectional views of electrodes having a different double-layer structure according to some embodiments of this disclosure are shown.

[0014] [Figure 3C] The following are cross-sectional views of electrodes having a three-layer structure according to several embodiments of this disclosure.

[0015] [Figure 4] The present disclosure shows a porous substrate coated with a catalyst layer according to several embodiments.

[0016] [Figure 5] This disclosure describes a method for forming electrodes for a metal-hydrogen battery according to several embodiments of this disclosure.

[0017] [Figure 6] An embodiment of a method for forming an electrode for a metal-hydrogen battery as shown in FIG. 5 is shown.

[0018] [Figure 7] An embodiment of a method for forming an electrode for a metal-hydrogen battery as shown in FIG. 5 is shown.

[0019] [Figure 8] An embodiment of a method for forming an electrode for a metal-hydrogen battery as shown in FIG. 5 is shown.

[0020] [Figure 9] An embodiment of a method for forming an electrode for a metal-hydrogen battery as shown in FIG. 5 is shown.

[0021] [Figure 10] FIGS. 10A-D are scanning electron microscope (SEM) images showing that the surface of an electrode having a higher double layer capacitance (Cdl) has a rougher surface according to some embodiments.

[0022] [Figure 11A] A consistent catalyst loading achieved by using a plating bath having a higher metal concentration according to some embodiments of the present disclosure is shown.

[0023] [Figure 11B] A diagram showing the capacitance-voltage curves of three battery cells formed with electrodes according to some embodiments of the present disclosure.

[0024] [Figure 11C] A diagram showing the efficiency-cycle number curves of three battery cells according to one exemplary embodiment.

[0025] [Figure 12A] An image of a porous layer showing waveform surface features according to some embodiments of the present disclosure.

[0026] [Figure 12B] These are SEM images showing a porous substrate before the compression process according to some embodiments of the present disclosure.

[0027] [Figure 12C] These are SEM images showing a compressed porous substrate according to several embodiments of the present disclosure.

[0028] [Figure 12D] This figure shows the voltage-capacity curves of a 10Ah battery using a three-layer electrode according to some embodiments of the present disclosure.

[0029] [Figure 13A] This figure shows a battery cell having electrodes that are not coated by surface affinity modification (e.g., wet-proofing coating) according to several embodiments.

[0030] [Figure 13B] This figure shows that, according to some embodiments of the present disclosure, the battery cell after the wet-proof coating step exhibits significantly improved discharge characteristics compared to the battery cell shown in Figure 13A.

[0031] [Figure 14] The stable cycle of a battery having electrodes according to several embodiments is illustrated.

[0032] [Figure 15] The voltage-to-capacity ratio of batteries being cycled at a wide range of charge rates (C rates) using electrodes, according to several embodiments, is shown.

[0033] [Figure 16] The long-term cycle performance of another battery having electrodes, according to several embodiments, is illustrated. [Modes for carrying out the invention]

[0034] The following description includes certain specific details in order to provide a complete understanding of the various embodiments of the Disclosure. However, those skilled in the art will understand that the Disclosure may be implemented without these details. Furthermore, although various embodiments of the Disclosure are disclosed herein, many adaptations and modifications can be made within the scope of the Disclosure according to the common general knowledge of those skilled in the art. Such modifications include the substitution of known equivalents to any embodiment of the Disclosure in substantially the same way and to achieve the same results.

[0035] Unless the context requires a different interpretation, the word “includes” and its variations, such as “equipped with” and “equipped with,” throughout this specification and the claims should be interpreted in the open, inclusive sense of “includes,” and should be interpreted as “includes, but not limited to.” Numerical ranges throughout the specification are intended to function as abbreviations for referring to each individual value that falls within the range containing the value defining the range, and each individual value is incorporated into the specification as it is individually described herein. In addition, the singular forms “one,” “one,” and “the said” include multiple references unless the context clearly indicates otherwise.

[0036] Throughout this specification, any reference to “one embodiment” or “embodiment” means that a particular feature, structure, or characteristic described in relation to the embodiment is included in at least one embodiment of the present invention. Therefore, the occurrence of the phrase “in one embodiment” or “in an embodiment” in various places throughout this specification does not necessarily refer to the same embodiment, but could be any example. Furthermore, special features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0037] Embodiments of the present disclosure describe electrodes for metal-hydrogen cells formed from one or more porous layers. Each porous layer comprises a porous substrate and a catalyst layer covering the porous substrate, the catalyst layer comprising a transition metal. At least one of the one or more porous layers includes a surface having features that facilitate hydrogen gas transport. In some embodiments, the anode electrode comprises a first porous layer having a first surface and a second porous layer adjacent to the first porous layer having a second surface, wherein the first surface of the first porous layer and the second surface of the second porous layer form a hydrogen gas transport channel.

[0038] Figure 1A shows a schematic diagram of an individual pressure vessel (IPV) metal-hydrogen cell 100 in which embodiments of the present disclosure can be used. The metal-hydrogen cell 100 has an electrode stack assembly 130 including stacked electrodes separated by a separator 106. The electrode stack assembly 130 has alternately stacked cathode electrodes 102 and anode electrodes 104, as shown in Figure 1A. The cathode electrodes 102 and anode electrodes 104 are separated by a separator 106 positioned between them. The separator 106 can be saturated with an electrolyte membrane 108. In some embodiments, in addition to electrically isolating the cathode electrode 102 from the anode electrode 104, the separator 106 provides a reservoir of the electrolyte membrane 108 that buffers the electrodes from either drying or flooding during the operation of the cell 100.

[0039] As shown in Figure 1A, the electrode stack assembly 130 can be housed in a pressure vessel 109. As illustrated, the electrolyte membrane 108 is placed in the pressure vessel 109 so that the stack 130 is saturated with the electrolyte membrane 108. The cathode electrode 102, anode electrode 104, and separator 106 are porous, thereby holding the electrolyte membrane 108 and allowing ions in the electrolyte membrane 108 to move between the cathode electrode 102 and the anode electrode 104. In some embodiments, the separator 106 can be omitted as long as the cathode electrode 102 and the anode electrode 104 are electrically insulated from each other and sufficient electrolyte membrane 108 is held within the electrode stack 130. For example, the space occupied by the separator 106 may be filled with the electrolyte membrane 108.

[0040] The metal-hydrogen cell 100 shown in Figure 1A may further include a filling tube 122 configured to introduce an electrolyte or gas (e.g., hydrogen) into a pressure vessel 109. The filling tube 122 may include one or more valves (not shown) for controlling the inflow and outflow of the pressure vessel 109 into and out of the enclosure, or the filling tube 122 may be sealed in another manner after the electrolyte membrane 108 and hydrogen gas have been filled into the pressure vessel 109.

[0041] As shown in Figure 1A and discussed above, the electrode stack assembly 130 has several stacks of alternating cathode electrodes 102 and anode electrodes 104 separated by a separator 106. The electrodes in the electrode stack assembly 130 can be coupled in parallel or in series, but in the example of battery 100 shown in Figure 1A, the electrodes are coupled in parallel. In particular, each of the cathode electrodes 102 is coupled to conductor 118, and each of the anode electrodes 104 is coupled to conductor 116. Although Figure 1A shows that the filling tube 122 is located on the side of conductor 118, the filling tube 122 may alternatively be located on the side of conductor 116, or somewhere in the pressure vessel 102.

[0042] As further shown in Figure 1A, the conductor 116 coupled to the anode electrode 104 is electrically coupled to a feedthrough terminal 120 that provides one terminal of the battery 100. Terminal 120 may have a feedthrough that allows terminal 120 to extend outside the pressure vessel 102, or, in particular, since terminal 120 is coupled to the anode electrode 104, the conductor 116 may be directly connected to the pressure vessel 109. Similarly, the conductor 118 coupled to the cathode electrode 102 may be coupled to a feedthrough terminal 124 that represents the opposite (positive) terminal of the battery 100. Since terminal 124 is coupled to the cathode electrode 104, terminal 124 may extend outside the pressure vessel 109 by passing through an insulated feedthrough.

[0043] As shown in Figure 1A, the electrode stack 104 can be fixed within the frame 132. In Figure 1A, the electrode stack assembly 130 can be configured to have anode electrodes 104 on both sides adjacent to the frame 132 in order to isolate the cathode electrode 102 from the frame 132. In some embodiments, particularly when the electrode stack assembly 130 is positioned so that the cathode electrode 102 is adjacent to the frame 132 rather than the anode electrode 104, a separator 106 may be provided adjacent to the frame 132 for further separation.

[0044] As described above, the electrode stack 130 has alternating layers of cathode electrodes 102 and anode electrodes 104 separated by a separator 106. The electrode stack assembly 130 is placed in a pressure vessel 109 and includes an electrolyte membrane 108, in which ions can move between the cathode electrodes 102 and anode electrodes 104. The separator 106 can be a porous insulator. In some embodiments, the electrolyte membrane 108 is an alkaline (pH greater than 7) aqueous electrolyte membrane.

[0045] Figure 1B shows several embodiments of the cathode electrode 102. The cathode electrode 102 may have one or more cathode porous layers 140, each of which is formed from a conductive substrate 114 covered with a coating 116. The coating 116 may be a redox reactive material containing a transition metal, as will be discussed further below. Similarly, as shown in Figure 1C, the anode electrode 104 may have one or more anode porous layers 142, each of which includes a porous conductive substrate 110 covered with a catalyst layer 112. Thus, as shown in Figure 1B, the cathode electrode 102 can be formed from one or more cathode porous layers 140. As shown in Figure 1C, the anode electrode 104 can be formed from one or more anode porous layers 142.

[0046] In some embodiments, the anode electrode 104 is a catalytic hydrogen electrode. As shown in Figure 1C, in some embodiments, the anode electrode 104 has a stack of porous layers 142, each porous layer 142 comprising a porous conductive substrate 110 and a catalyst layer 112 covering the porous conductive substrate 110. The catalyst layer 112 may include a dual-function catalyst for catalyzing both the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR) in the anode electrode 104. In some embodiments, the porous conductive substrate 110 has a porosity of at least about 10%, at least about 20%, at least about 30%, at least about 40%, or at least about 50%, up to about 80%, up to about 90%, 95%, or more. In some embodiments, the porous conductive substrate 110 can be a metal foam such as nickel foam, iron foam, copper foam, or steel foam. In some embodiments, the porous conductive substrate 110 is a metal alloy foam such as nickel-molybdenum foam, nickel-iron foam, nickel-copper foam, nickel-cobalt foam, nickel-tungsten foam, nickel-silver foam, or nickel-molybdenum-cobalt foam. The porous conductive substrate 110 can also be formed from other conductive substrates, such as metal foil, metal mesh, or fibrous conductive substrates. In some embodiments, the conductive substrate 110 can also be formed from carbon-based materials such as carbon fiber paper, carbon cloth, carbon felt, carbon mat, carbon nanotube film, graphite foil, graphite foam, graphite mat, graphene foil, graphene fiber, graphene film, or graphene foam.

[0047] In some embodiments, the binary-function catalyst of catalyst layer 112 may be a nickel-molybdenum-cobalt (NiMoCo) alloy. Other transition metals or metal alloys may be binary-function catalysts, such as nickel, nickel-molybdenum, nickel-tungsten, nickel-tungsten-cobalt, nickel-tungsten-copper, nickel-carbon, nickel-chromium, or base composite materials. In some embodiments, the binary-function catalyst of catalyst layer 112 may have a transition metal alloy containing two or more of Ni, Co, Cr, Mo, Fe, Mn, Cu, Zn, Sn, and W. Other noble metals and their alloys, such as platinum, palladium, iridium, gold, rhodium, ruthenium, rhenium, osmium, silver, and their alloys may be combined with non-noble transition metals, such as platinum, palladium, iridium, gold, rhodium, ruthenium, rhenium, osmium, silver, nickel, cobalt, manganese, iron, molybdenum, tungsten, chromium, etc. In some embodiments, the binary-function catalyst of catalyst layer 112 may be a combination of a HER catalyst and a HOR catalyst. In some embodiments, the binary-function catalyst of catalyst layer 112 may include a mixture of different materials, such as transition metals and their oxides / hydroxides, which contribute collectively to hydrogen evolution and oxidation reactions. In some embodiments, catalyst layer 112 includes nanostructures of the binary-function catalyst having sizes (or average sizes) in the range of approximately 1 nm to approximately 100 nm, approximately 1 nm to approximately 80 nm, or approximately 1 nm to approximately 50 nm. In some embodiments, catalyst layer 112 includes microstructures of the binary-function catalyst having sizes (or average sizes) in the range of approximately 100 nm to approximately 500 nm, or approximately 500 nm to approximately 1000 nm.

[0048] In some embodiments, the anode electrode 104 may have a single-layer or multi-layer structure, as described above in Figure 1C. In some embodiments, the anode electrode 104 may be formed with a flat or non-uniform surface, or a combination of flat and non-uniform peripheral surfaces may form multiple layers. Embodiments of the present disclosure include at least one porous layer 142 having a surface characterized by a non-uniform surface.

[0049] Figure 2 shows a cross-sectional view of one embodiment of an anode electrode 104 having a single-layer porous layer 302. The single-layer porous layer 302 includes an uneven upper surface 302a and a lower surface 302b. The upper surface 302a and the lower surface 302b can be formed to have different characteristics. The uneven surfaces 302a and 302b can increase the surface reaction sites for HER and HOR, facilitate hydrogen gas transport to and from the surface of the anode electrode 104, and improve the performance of the anode electrode 104. The uneven surfaces 302a and 302b may be symmetrical or asymmetrical. In some embodiments, the uneven surfaces 302a and 302b of the single-layer structure 302 can be formed by pressing or stamping a rectangular parallelepiped substrate against the electrode porous substrate 110 to create a desired surface contour. In some embodiments, the characteristics of surface 302a may include, for example, a corrugated surface. In some embodiments, the characteristics of surface 302b may be smooth or flat, or corrugated. The formation of features on surfaces 302a and 302b may be achieved before the application of the catalyst coating 112, or, in some embodiments, after the catalyst coating 112. As shown in Figure 2, according to one exemplary embodiment, the features of the uneven surfaces 302a and 302b may be corrugated surfaces. Other surface contour features may also be formed. For example, surfaces 302a and 302b may include rounded hills and / or valleys, notches, corrugations, or other features. In some embodiments, one of surfaces 302a and 302b may be configured to be flat or smooth. As described below with respect to Figure 2, the single-layer structure 302 may include a porous substrate 110 formed of a metal or metal alloy foam. The surface contour of the single-layer structure 302 in Figure 2 (e.g., corrugated surface or other characteristic surface) is shown in macroscopic view. In microscopic view, the surface of the single-layer structure 302 includes a plurality of micropores and / or nanopores.

[0050] Embodiments of the anode electrode 104 according to several embodiments include any number (one or more) porous layers 142, at least one of which has a surface with heterogeneous features. These heterogeneous features can be formed by pressing or stamping the porous conductor 110 of the porous layer 142. Heterogeneous surfaces may include features such as corrugations, rounded hills, notches, grooves, or other shapes that make the surface topology heterogeneous. Figures 3A to 3C show several embodiments of the anode electrode 104. However, it should be understood that any stacking of porous layers 142 that forms a channel to facilitate the flow of hydrogen gas can be used. For example, Figure 2 shows a single-layer anode electrode 104 having a corrugated surface, for example. Figure 3A shows an embodiment of the anode electrode 104 having two porous layers 142, Figure 3B shows another embodiment of the anode electrode 104 having two porous layers 142, and Figure 3C shows an embodiment of the anode electrode 104 having three porous layers 142. However, the embodiment of the anode electrode layer 104 may also include three or more layers.

[0051] Figure 3A shows a cross-sectional view of an anode electrode 104 having a double-layer structure 304 (i.e., two porous layers 142) according to several embodiments. The double-layer structure 304 of the anode electrode 104 includes a first porous layer 306 and a second porous layer 308 stacked adjacent to each other. In the illustrated embodiment, the first porous layer 306 is similar to the single-layer structure 302 shown in Figure 2 and includes a non-uniformly characterized upper surface 306a and lower surface 306b. The second porous layer 308 is configured to have a smooth and flat surface (e.g., the lower surface 308a is smooth / flat). The configuration of the first porous layer 306 adjacent to the second layer 308 forms a plurality of channels 310 between surface 306a and surface 308a, depending on the features formed on surface 306a of the porous layer 306. For example, a corrugated porous layer 306 forms channels 310. The channels 310 can be formed to have other features, as described above. As described above, the channel 310 can facilitate the movement of hydrogen gas in the HOR and HER. In some embodiments, the porosity of the first porous layer 306 and the second porous layer 308 may also differ. As described below with respect to Figure 4, each of the first layer 306 and the second layer 308 may include a porous substrate 110 (e.g., a metal or alloy foam) coated with a catalyst layer 112. The flat or non-uniform surfaces of the first layer 306 and the second layer 308 in Figure 3A are shown in macroscopic view. In microscopic view, the surface contains a plurality of micropores and / or nanopores.

[0052] In some embodiments, the channel may also be generated by stacking two porous layers 142, each having non-uniform surface features between different layers. An embodiment of the anode electrode 104 illustrating this embodiment is shown in Figure 3B. Figure 3B shows a cross-sectional view of the anode electrode 104 having a double-layer structure 311 (two porous layers 142) according to some embodiments. The double-layer structure 311 includes a first porous layer 312 and a second porous layer 314 stacked adjacent to each other. As shown in Figure 3B, both the first porous layer 312 and the second porous layer 314 of the anode electrode 104 are similar to the single-layer structure 302 shown in Figure 2. The first porous layer 312 includes an upper surface 312a and a non-uniform lower surface 312b. The second porous layer 304 includes an uneven upper surface 314a and a lower surface 314b. The upper surface 312a and the lower surface 314b may themselves contain non-uniform features, or they may be flat or smooth. The configuration of the first porous layer 312 and the second porous layer 314 forms a plurality of channels 310 between the surface 312b of the first porous layer 312 and the surface 314a of the second porous layer 314. These channels 310 can facilitate the movement of hydrogen gas in the HOR and HER. Other configurations of the first porous layer 312 and the second porous layer 314 are also possible, as long as channels can be formed at their interface when the first porous layer 312 and the second porous layer 314 are stacked. In some embodiments, the porosity of the first porous layer 312 and the second porous layer 314 may be different. As described below with reference to Figure 4, each of the first porous layer 312 and the second porous layer 314 may include a porous substrate 110 (e.g., a metal or metal alloy foam) and a catalyst layer 112 covering the porous substrate 110. The uneven surfaces of the first porous layer 312 and the second porous layer 314 shown in Figure 3B are shown macroscopically. In the microscopic view, the surface contains multiple micropores and / or nanopores.

[0053] Figure 3C shows a cross-sectional view of an anode electrode 104 having a three-layer structure 320 (i.e., three porous layers 142) according to several embodiments. The three-layer structure 320 includes a first porous layer 322, a second porous layer 324, and a third porous layer 326 interposed between the first porous layer 322 and the second porous layer 324. The first porous layer 322, the second porous layer 324, and the third porous layer 326 each have a first porosity, a second porosity, and a third porosity, respectively, where the third porosity may be the same as, less than, or greater than the first and second porosities.

[0054] In some embodiments, the surface contours of the first porous layer 322, the second porous layer 324, and the third porous layer 326 are configured such that, when they are stacked together, a plurality of channels 310 are generated at the interfaces between the first porous layer 322 and the third porous layer 326 (e.g., the first channel), and between the second porous layer 324 and the third porous layer 326 (e.g., the second channel). These channels 310 can facilitate the movement of hydrogen gas in the HOR and HER. In the illustrated embodiment shown in Figure 3C, the surface 322a of the first porous layer 322 facing the third porous layer 326 can be configured to be smooth and flat, while the surface 326a of the third porous layer 326 facing surface 322a can be configured to be heterogeneous (e.g., corrugated, notched, rounded hills and / or valleys, grooves, or other features) so that at least one channel 310 is formed between them. Furthermore, the surface 324a of the second porous layer 324 facing the third porous layer 326 can be configured to be smooth and flat, while the surface 326b of the third porous layer 326 facing surface 324a can be configured to be non-uniform (including, for example, corrugated, notched, or other such features) so that at least one channel 310 is formed between them.

[0055] It should be understood that the embodiments shown in Figures 2 and 3A-3C are merely illustrative and not limiting. Other configurations are possible. For example, each of the embodiments shown in Figures 2 and 3A-3C may include an additional porous layer 142. Furthermore, although surfaces 326a and 326b are shown as corrugated, other surface contours can be used if the surface contour can facilitate the generation of gas channels at the interface. In some embodiments, at least one of surfaces 322a and 326a is heterogeneous so that at least one gas channel can be generated between them, and / or at least one of surfaces 324a and 326b is heterogeneous so that at least one gas channel can be generated between them. In some embodiments, the contours of surfaces 322a and 326a are configured to be different from each other so that at least one gas channel can be created between them, and / or the contours of surfaces 324a and 326b are configured to be different from each other so that at least one gas channel can be created between them. Furthermore, although the anode electrode 104 is illustrated to have three porous layers, the disclosure is not limited to this structure. For example, the anode electrode 104 may include an upper stack of two first porous layers 322, a bottom stack of two second porous layers 324, and one or more third porous layers 326 interposed between the upper and bottom stacks. In some embodiments, a gas diffusion layer may be located between the first porous layers 322 and the third porous layer 326, and / or between the second porous layer 324 and the third porous layer 326. For example, the gas diffusion layer may be porous.

[0056] In some embodiments, the first porous layer 322 and the second porous layer 324 may be configured to have non-uniform surfaces (including, for example, corrugated, notched, or other features) similar to the surfaces 326a and 326b of the third porous layer 326. The corrugated surfaces of two adjacent layers are arranged to face each other, thereby forming a channel 310. In some embodiments, the anode electrode 104 can be formed from any one or any two of the first porous layer 322, the second porous layer 324, and the third porous layer 326.

[0057] In some embodiments, at least one of the catalyst layers in the anode electrode 104 can be partially coated with a surface affinity modifying material to create different affinities with respect to the electrolyte (e.g., electrolyte 108) in the porous layer 142. For example, in the structure 320 shown in Figure 3C, at least one of the porous layers 322, 324, and 326 is coated with a surface affinity modifying material. If the catalyst layer on the porous substrate 142 is hydrophilic with respect to the electrolyte, the catalyst layer 112 may be partially coated with a material that is hydrophobic with respect to the electrolyte 108. Conversely, if the catalyst layer 112 on the porous substrate is hydrophobic with respect to the electrolyte, the catalyst layer may be partially coated with a material that is hydrophilic with respect to the electrolyte. This structure can facilitate the movement of hydrogen gas within the pores of the electrode and improve HOR during discharge.

[0058] Referring to Figure 4, in some embodiments, each of the first porous layers 142 (or the layered structures shown in Figures 2, 3A, and 3B) comprises a porous substrate 410 and a catalyst layer 412 coated on the porous substrate 410, the catalyst layer 412 comprising a transition metal alloy. The porous substrate 410 is similar to the porous conductive substrate 110 in Figure 1C and, as described above, may include a metal foam or a metal alloy foam. The catalyst layer 412 is similar to the catalyst layer 112 in Figure 1C. Thus, the surface contours in Figures 2 and 3A-3C are shown in macroscopic views. Each of these surfaces comprises a plurality of micropores and / or nanopores 414, as shown in Figure 4.

[0059] As described above, the catalyst layer 112 may include a transition metal or metal alloy catalyst. Furthermore, to avoid anode flooding, where pores in the anode are filled with the electrolyte membrane, a polymer material can be coated onto the catalyst layer to provide a wet-proofing effect. In some embodiments, the polymer material includes partially or fully fluorinated polymers such as polyethylene, polypropylene, and other fluorinated polymers, e.g., polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), polyethylene tetrafluoroethylene (ETFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), etc. The electrodes for the metal-hydrogen cell may be coated with a surface affinity modifier, but the surface affinity modifier is not configured to cover the entire surface of the catalyst layer. For example, the surface affinity modifier can cover up to 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, or 70% of the total surface of the catalyst layer.

[0060] Referring back to Figure 1B, the cathode electrode 102 may include a conductive substrate 114 and a coating 116 covering the conductive substrate 114. The coating 116 includes a redox reactive material containing a transition metal. In some embodiments, the conductive substrate 114 is porous, having a porosity of, for example, at least about 10%, at least about 20%, at least about 30%, at least about 40%, or at least about 50%, and up to about 80%, up to about 90%, or more. In some embodiments, the conductive substrate 114 may be formed from a metal foam, such as nickel foam, or a metal alloy foam. Other conductive substrates, such as metal foils, metal meshes, and fibrous conductive substrates, are also included in this disclosure. In some embodiments, the transition metal included in the redox reactive material is nickel. In some embodiments, nickel is included, for example, as nickel hydroxide or nickel oxyhydroxide. In some embodiments, the transition metal included in the redox reactive material may be cobalt. In some embodiments, cobalt is included as cobalt oxide or zinc cobalt oxide. In some embodiments, the transition metal included in the redox-reactive material may be manganese. In some embodiments, manganese may be included as manganese oxide or doped manganese oxide (e.g., doped with nickel, copper, bismuth, yttrium, cobalt, or other transition metals or post-transition metals). Other transition metals such as silver are also included in this disclosure. In some embodiments, the coating microstructure of the redox-reactive material may have sizes (or average sizes) in the range of, for example, about 1 μm to about 100 μm, about 1 μm to about 50 μm, or about 1 μm to about 10 μm.

[0061] In some embodiments, the electrolyte membrane 108 is an aqueous electrolyte. The aqueous electrolyte is alkaline and has a pH greater than 7, for example, about 7.5 or higher, about 8 or higher, about 8.5 or higher, about 9 or higher, about 11 or higher, or about 13 or higher. In non-limiting examples, the electrolyte membrane 108 may contain KOH or NaOH or LiOH, or a mixture of LiOH, NaOH and / or KOH.

[0062] Figure 5 shows an embodiment of method 500 for forming an embodiment of the anode electrode 104. In step 502, one or more porous substrates 110 are obtained. The number of porous substrates 110 processed determines the number of porous layers 142 in the anode electrode 104. The porous substrates 110 may be conductive, as described above. In some embodiments, metal foams such as nickel foam, copper foam, iron foam, steel foam, and aluminum foam can be used to form the porous substrates 110. In some embodiments, the porous substrate 110 is a nickel-containing metal alloy foam such as nickel-iron foam, nickel-molybdenum foam, nickel-copper foam, nickel-cobalt foam, nickel-tungsten foam, nickel-silver foam, and nickel-molybdenum-cobalt foam. As described above, the porous substrate 110 can also be formed from other materials such as porous metal foil, metal mesh, and fibrous conductive substrates. Furthermore, in some embodiments, the porous substrate 110 can be formed from carbon-based materials such as carbon fiber paper, carbon cloth, carbon felt, carbon mat, carbon nanotube film, graphite foil, graphite foam, graphite mat, graphene foil, graphene fiber, graphene film, and graphene foam. The porous substrate 110 may have a porosity of at least about 10%, at least about 20%, at least about 30%, at least about 40%, or at least about 50%, and up to about 80%, up to about 90%, or more. Porous substrates 110 having different porosities can be utilized.

[0063] In step 504, the porous substrate 110 can be modified. Modification of the porous substrate 110 can be carried out in many ways, including adjusting the surface morphology of the porous substrate 110, adjusting the porosity of the porous substrate 110, other processes, and various combinations of these processes. Some of the processes that can be performed in modification step 504 are described further below. Furthermore, if there are multiple porous substrates 110 being processed, the processes performed on each individual porous substrate 110 in modification step 504 may differ from those of the others.

[0064] In step 506, each of the porous substrates prepared in modification step 504 is coated with a catalyst layer 112, for example, by electroplating. The catalyst layer 112 may contain two or more transition metals such as Ni, Co, Cr, Mo, Fe, Zn, Sn, and W. In some embodiments, the catalyst layer 112 contains a nickel-molybdenum-cobalt (NiMoCo) alloy or another alloy as described above. In some embodiments, the entire surface of the porous substrate is coated with the catalyst layer 112. In some mounting configurations, the catalyst layer 112 does not have to cover the entire surface of the porous substrate 110. In the electroplating process, the catalyst layer can be formed by performing electroplating in a bath containing the transition metal. In some embodiments, the plating bath may be a solution of a salt such as nickel, molybdenum, or cobalt having a concentration in the range of 0.1 to 100 g / liter (grams / liter). The plating bath solution may also contain pH buffering salts such as sodium bicarbonate with a concentration in the range of 1 to 100 g / liter, and possibly other salts such as sodium pyrophosphate with a concentration of 1 to 100 g / liter, which helps stabilize the plating bath solution.

[0065] The deposition of the catalyst layer 112 in step 506 can also be carried out by a chemical reduction method or physical vapor deposition (PVD) method such as sputtering, electron beam deposition, or chemical vapor deposition (CVD), atomic layer deposition (ALD), or other methods. Furthermore, as described above, the catalyst may be a binary-function catalyst as described above.

[0066] In step 508, the porous layer 142 produced in step 506 is further processed. Such processing may include, for example, leaching, annealing, surface affinity coating (wet proofing), other processing, and any combination thereof. In addition, if there are multiple porous layers 142 being processed, the processing performed on each individual porous layer 142 may differ from one another.

[0067] In step 510, one or more porous layers 142, each coated with the catalyst layer obtained from step 508, are connected / bonded to each other to form an anode electrode 104 for the metal-hydrogen cell 100. The resulting anode electrode 104 may be one of those described above with respect to Figures 2 and 3A-3C. As shown in Figures 3A-3C, each of the porous layers 104 connected in step 508 may undergo different treatments in method 508.

[0068] While operations 502–510 are shown in a specific sequence in Figure 5, it should be further understood that this disclosure is not so limited. Operations 502–510 may be performed in different orders to form the same or similar electrodes. Figure 5 is for illustrative purposes only and is not intended to limit the order of operations.

[0069] Figures 6–9 illustrate various embodiments of Method 500. While Figures 6–9 illustrate various individual processes, it should be understood that Method 500 used to manufacture a particular embodiment of the anode electrode 104 may include any combination or all of the processes discussed herein.

[0070] Figure 6 shows Method 600, which is an example of Method 500 for forming an anode electrode 104 for a metal-hydrogen cell 100. As described above, in step 502, one or more porous substrates 110 are obtained. In step 504, each of the porous substrates 110 can be modified. In step 506, the modified porous substrates 110 are coated with a catalyst layer 112, for example by electroplating, to form a porous layer 142. In step 508, the porous layer 142 undergoes further processing. In Method 600 of this embodiment, processing step 508 may include a metal leaching process 602 to remove some metal from the catalyst layer 112 of the porous layer 142. In some embodiments, an annealing step 604 may be performed after the metal leaching process 602 during processing step 508. In step 510, one or more porous layers 142, each formed from a porous substrate 110 coated with a catalyst layer 112, are connected / bonded to each other to form an anode electrode 104 for the metal-hydrogen cell 100.

[0071] In the leaching step 602 of step 504, the porous layer 142 formed from the porous substrate 110 coated with the catalyst layer 112 can be immersed in an alkaline solution (e.g., a KOH solution) to selectively leach certain metals from the catalyst layer 112. This procedure results in a high surface area with a high density of active HOR / HER moieties per unit area. In some embodiments, the leaching process may be accelerated by carrying out the leaching at a temperature above room temperature, for example, at about 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C, or between any two of the above values. In some embodiments, if the catalyst of the catalyst layer 112 is a NiMoCo alloy, the leaching operation can remove some (but not all) of the Mo from the NiMoCo alloy. Metal leaching is not limited to high pH plating solutions and can be carried out using plating solutions across the entire pH range (0-14) according to the solubility of the target metal. For example, Ni can be leached in an acidic solution (pH < 7) to increase its surface area. The leaching tank may also contain an oxidizing or reducing agent to facilitate the dissolution of metal from pure metal or alloy. As further shown in Figure 6, in some embodiments, an annealing step 604 may be performed after the leaching step 602, where the porous layer is sent to an oven and annealed in a diluted hydrogen atmosphere to deoxidize the surface. Annealing may be performed at a temperature similar to that of the leaching step (e.g., above 100°C). In some embodiments, the annealing step 604 may be performed in a diluted atmosphere at 100°C to 500°C, for example, 400°C.

[0072] Figure 7 shows method 700, which is another embodiment of method 500 for forming an anode electrode 104 for a metal-hydrogen cell 100. As described above, in step 502, one or more porous substrates 110 are obtained. In step 504, each of the porous substrates 110 can be modified. In the exemplary embodiment shown in Figure 7, at least some of the porosity of the porous substrates 110 is changed in step 702. In step 506, the porous substrates 110 are coated with a catalyst layer 112, for example, by electroplating as described above. In step 508, the porous layers 142 formed from the porous substrates 110 coated with the catalyst layer 112 can be subjected to further processing. As described above, in step 510, one or more of the one or more porous layers 142 formed from the porous substrates 110 coated within the catalyst layer 112 are connected / bonded to each other to form an anode electrode 104 for a metal-hydrogen cell 100 as described above.

[0073] In some embodiments, step 702 of processing step 504 can reduce the porosity of one or more porous substrates among the porous substrates 110, for example, by compression of the porous support 110. For example, one or more porous substrates 110 obtained in step 502 to form the anode electrode 104 in step 510 can undergo a compression process to adjust their porosity. Compression can also provide more rigid porous substrates 110 for forming the anode electrode 104. In some embodiments, the porous substrates 110 may be compressed to different porosities depending on the embodiment of the anode electrode 104 obtained. The higher the compression applied to the porous substrate, the lower the porosity. For example, the porous substrate 110 terminating on the outermost edge of the anode electrode 104 may be compressed to a greater extent than the porous substrate 110 located within the outermost porous substrate 110 of the anode electrode 104. In some embodiments, the internal porous substrate 110 may or may not undergo the compression process in step 702. This configuration involves higher compression in the outer porous layer 142 than in the inner porous layer, creating rigidity on the outside of the anode electrode 104 and providing a highly porous portion on the inside of the anode electrode 104, thereby facilitating the flow of fluid or gas for HER and HOR.

[0074] Figure 8 shows method 800, which is another embodiment of method 500 for forming an anode electrode 104 for a metal-hydrogen cell 100. As described above, in step 502, one or more porous substrates 110 are obtained. In step 504, each of the porous substrates 110 can be modified. In the exemplary embodiment shown in Figure 8, at least some surface morphologies of the porous substrate 110 are modified in step 802 to form surface features as described above. In step 506, the porous substrate 110 is coated with a catalyst layer 112, for example by electroplating as described above, to form a porous layer 142. In step 508, the porous layer 142 formed from the porous substrate 110 coated with the catalyst layer 112 can be subjected to further processing. As described above, in step 510, one or more porous layers 142, each formed from the porous substrate 110 coated within the catalyst layer 112, are connected / bonded to each other to form an anode electrode 104 for a metal-hydrogen cell 100 as described above.

[0075] In the surface modification step 802, the surface contour of one or more porous substrates 110 can be modified such that one or more channels (e.g., channels 310 in Figures 3A-3C) are formed at the interface of two adjacent porous layers 142. For example, one or more porous substrates 110 may be punched out on their surfaces to produce different surface morphologies for two adjacent surfaces of two adjacent porous substrates 110. For example, one of the two adjacent surfaces may be configured to be rough / uneven, while the other of the two adjacent surfaces may be configured to be smooth / flat. The surface of the porous substrate 110 may be any of a variety of shapes, such as corrugated, alternating unevenness, spiked, grooved, notched, rounded, or other shapes. Other methods that can be used to form different surface morphologies include etching, cutting, scratching, or other methods for forming surface morphologies. In some embodiments, the morphing step 802 and the porosity step 702 can be combined into a single pressing or stamping step that results in the formation of the surface morphology and the adjustment of the porosity of the porous substrate 110.

[0076] Figure 9 shows method 900, which is another embodiment of method 500 for forming an anode electrode 104 for a metal-hydrogen cell 100. As described above, in step 502, one or more porous substrates 110 are obtained. In step 504, each of the porous substrates 110 can be modified. In step 506, the porous substrates 110 are coated with a catalyst layer 112, for example by electroplating as described above, to form a porous layer 142. In step 508, the porous layer 142 formed from the porous substrates 110 coated with the catalyst layer 112 can be subjected to further processing. As shown in Figure 9, step 508 may include a surface affinity coating step 902, as will be described further below. As described above, in step 510, one or more porous layers 142, each formed from the porous substrates 110 coated within the catalyst layer 112, are connected / bonded to each other to form an anode electrode 104 for a metal-hydrogen cell 100 as described above. In step 902 of step 508, a surface affinity modifying material is coated onto the catalyst layer.

[0077] In some embodiments, step 902 may involve partially coating the catalyst layer 112 on the porous substrate 111 with a material that is hydrophobic with respect to the electrolyte 108, when the catalyst layer 112 on the porous substrate 111 is hydrophobic with respect to the electrolyte. In some embodiments, the catalyst layer 112 on the porous substrate 110 may be partially coated with a material that is hydrophobic with respect to the electrolyte 108. The resulting structure facilitates the movement of hydrogen gas within the pores of the porous layer 142 of the anode electrode 104 and can avoid anode flooding. In some embodiments, the surface affinity modifying material coated in step 902 may be one or more polymers. As a non-limiting example, the surface affinity modifying material may include a hydrophobic polymer such as PTFE, as described above.

[0078] It should be understood that the methods disclosed herein can be partially or entirely modified or combined to make the electrodes suitable for use in metal-hydrogen cells. Specifically, method 500 may include any combination of processes as discussed in each of Figures 6 to 9. Specific examples are given below to illustrate further methods for forming the anode electrode 104 for the metal-hydrogen cell 100.

[0079] Example I: Increase in the number of active HOR / HER sites on the electrode surface In some embodiments, in step 506, a catalyst layer 112 can be formed by electrodeposition of a NiMoCo alloy onto the porous electrode 110. In these embodiments, the resulting porous layer 142, together with the porous substrate 110 and the catalyst layer 112, can be immersed in a concentrated KOH solution to selectively leach a portion of the Mo in step 602, as shown in Figure 6. This process can result in a high surface area with a high density of active HOR / HER moieties per unit area. A robust electrochemical impedance process can be developed, and the double-layer capacitance (C) can be further evaluated using an electron microscope. dl The surface area was estimated from ). Figures 10A to 10D show higher C dl This is a scanning electron microscope (SEM) image showing that a surface with C has a rougher surface. dl This correlates very strongly with the charge transfer resistance (Rct) of HOR / HER and can be used to quickly screen the quality of a batch of porous layers.

[0080] Example II: Electroplating Bath Composition The bath composition that can be used to electroplat the catalyst in step 506 can be changed by increasing the metal ion concentration by 2 to 5 times. Such an increase in metal ion concentration increases the load and performance of the catalyst. Higher metal ion concentrations can be used in many plating runs performed before the bath needs to be replenished. Figure 11A is mg / cm 2The mass load is shown against batch number, demonstrating a consistent catalytic load achieved by increased metal concentration without the need for frequent replenishment of the bath. Battery cells fabricated using this redesigned bath also showed strong performance. Figure 11B shows voltage-versus-capacitance graphs for several cells (cells 1, 2, and 3) formed with a pair of cathode electrodes 102 and anode electrodes 104, respectively, formed according to embodiments of this disclosure. Figure 11C shows the efficiency and capacity-versus-cycle count for the three cells shown in Figure 11B. Figures 11B and 11C demonstrate strong performance using the proposed bath composition.

[0081] Example III: Mo leaching from NiMoCo catalyst The above-described Mo leaching process step 602 can be performed on the porous substrate 110 in concentrated KOH on the porous layer after electroplating of the porous layer of the NiMoCo catalyst layer 112 to increase the active reaction sites on the surface area. Leaching process step 602 requires a longer time at room temperature than when performed at high temperature. Alternatively, step 602 may utilize an etching process. The same catalyst surface area and performance achieved with concentrated KOH can be achieved by etching at high temperature for a short time, for example, about 30 minutes.

[0082] Example IV: Three-layer electrode structure The three-layer anode structure, as shown in Figure 3C above, enables high-density catalyst sites and easy hydrogen gas transport without the need for a gas screen. As described above, the anode electrode 104 comprises three porous layers (layers 322, 324, and 326) stacked on top of each other. The hydrogen flow channel is formed by corrugating the intermediate layer 326 of the three porous substrates. Figure 12A is an image showing an example of the corrugated intermediate layer, layer 326. Figure 12B is an SEM image showing the porous substrate before compression in the porosity modification process 702 of Figure 7; Figure 12C is an SEM image showing the porous substrate 110 after compression in the porosity modification process 702 of Figure 7. Figure 12C also shows that the compressed porous substrate has a low porosity. Figure 12D is a graph showing the voltage-capacity curve of a 10Ah battery using the three-layer anode electrode 104 as shown in Figure 3C, demonstrating the strong performance when using the three-layer anode electrode 104.

[0083] Example V: Wet-proof anode using PTFE By performing the affinity coating step 902 of processing step 508, as shown in Figure 9, using an immersion and sintering process, hydrophobic regions can be induced on the anode porous layer 142, creating an optimal balance between electrolyte permeation and hydrogen gas transport without causing anode flooding. Figure 13A is a voltage-to-capacity diagram showing that a battery cell without a wet waterproof (affinity) coating is less likely to discharge due to anode flooding. The resulting battery is less likely to discharge due to anode flooding by the electrolyte membrane 108, which suppresses the HOR reaction by blocking hydrogen gas access to the electrode surface. Figure 13B is a voltage-to-capacity diagram showing that a battery cell in which the anode porous layer 142 contains a moisture-resistant coating (e.g., fluoropolymer) exhibits significantly improved discharge characteristics compared to the battery cell shown in Figure 13A.

[0084] Example VI: Stable battery performance at high temperatures Figure 14 shows an exemplary battery having one of three cells. Each cell includes an anode electrode 104 having a single-layer structure as shown in Figure 2. As shown in Figure 14, each cell can be stably cycled for more than 3000 cycles with stable performance at a charge level of 0.5C at 45°C.

[0085] Example VII: High C-rate performance Figure 15 shows a 16Ah cell having a three-layer anode electrode 104 as shown in Figure 3C. Figure 15 demonstrates that an embodiment of the battery 100 using the anode electrode 104 described above can easily and reliably operate at charge and discharge rates up to 5C without capacity loss.

[0086] Example VIII: Stable 2C cycle performance at room temperature Figure 16 shows a 20Ah cell having a double-layer anode electrode 104 as shown in Figure 3A, which can be cycled at a charging speed of 2C or more for over 1000 cycles with stable cell performance.

[0087] Disclosure method Aspects of this disclosure describe electrodes incorporating metal-metal hydride cells and their formation. A selection of numerous aspects of this disclosure may include the following:

[0088] Embodiment 1: An electrode for a metal-hydrogen battery, wherein the electrode comprises one or more porous layers, each of the porous layers comprising a porous substrate and a catalyst layer covering the porous substrate, the catalyst layer comprising a transition metal, and at least one of the at least one porous layer comprising a surface having characteristics that facilitate hydrogen gas transport.

[0089] Embodiment 2: The electrode according to Embodiment 1, wherein at least one porous layer comprises a plurality of porous layers, and the first surface of the first porous layer and the second surface having the characteristics of the second porous layer have contours that form hydrogen gas transport channels.

[0090] Embodiment 3: An electrode according to Embodiments 1 to 2, wherein each porous substrate of at least one porous layer comprises one or more of the following: metal or metal alloy foam, metal foil, metal mesh, fibrous conductive substrate, carbon fiber paper, carbon cloth, carbon felt, carbon mat, carbon nanotube film, graphite foil, graphite foam, graphite mat, graphene foil, graphene fiber, graphene film, and graphene foam.

[0091] Embodiment 4: The electrode according to Embodiments 1 to 3, wherein the metal or metal alloy foam is one of the following: nickel foam, nickel-molybdenum foam, nickel-iron foam, nickel-copper foam, nickel-cobalt foam, nickel-tungsten foam, nickel-silver foam, and nickel-molybdenum-cobalt foam.

[0092] Embodiment 5: The electrode according to Embodiments 1 to 4, wherein each porous substrate of at least one porous layer comprises a metal foam or a metal alloy foam.

[0093] Embodiment 6: The electrode according to Embodiments 1 to 5, wherein the catalyst layer is a dual-function catalyst that contributes to both the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR).

[0094] Embodiment 7: The electrode according to Embodiments 1 to 6, wherein the binary functional catalyst is one or more of nickel-molybdenum-cobalt (NiMoCo), nickel, nickel-molybdenum, nickel-tungsten, nickel-tungsten-cobalt, nickel-tungsten-copper, nickel-carbon, and nickel-chromium.

[0095] Embodiment 8: The electrode according to Embodiments 1 to 7, wherein the transition metal of the binary functional catalyst includes two or more of Ni, Co, Cr, Mo, Fe, Zn, Sn, and W.

[0096] Embodiment 9: An electrode according to Embodiments 1 to 8, wherein the bifunctional catalyst comprises one or more of platinum, palladium, iridium, gold, rhodium, ruthenium, rhenium, osmium, silver, nickel, cobalt, manganese, iron, molybdenum, tungsten, and chromium.

[0097] Embodiment 10: An electrode according to Embodiments 1 to 9, wherein the transition metal alloy is a NiMoCo alloy or a NiMo alloy.

[0098] Embodiment 11: An electrode according to Embodiments 1 to 10, wherein at least one porous layer comprises a first porous layer, a second porous layer, and a third porous layer disposed between the first porous layer and the second layer, and the third porous layer has a first surface contour different from the second surface contour of the first porous layer or the second porous layer.

[0099] Embodiment 12: An electrode according to Embodiments 1 to 11, wherein the features include one or more of the following: waveforms, notches, rounded hills and / or valleys, and grooves.

[0100] Embodiment 13: The electrode according to Embodiments 1 to 12, wherein at least one of the catalyst layers of the first porous layer, the second porous layer, and the third porous layer is at least partially covered with a moisture-proof material.

[0101] Embodiment 14: The electrode according to Embodiments 1 to 13, wherein the wet-proofing material comprises one of polyethylene, polypropylene, partially or fully fluorinated polymers, polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEB), polyethylene terephthalate tetrafluoroethylene (ETFE), polyvinyl fluoride (PVF), and polyvinylidene fluoride (PVDF).

[0102] Embodiment 15: An anode electrode comprising a first porous layer having a first surface and a second porous layer adjacent to the first porous layer having a second surface, wherein the first surface of the first porous layer and the second surface of the second porous layer form a hydrogen gas transport channel.

[0103] Embodiment 16: The anode electrode of Embodiment 15, wherein the first surface is flat or smooth and the second surface is heterogeneous.

[0104] Embodiment 17: An anode electrode according to Embodiments 15-16, wherein one or both of the first and second surfaces include an uneven shape.

[0105] Embodiment 18: An anode electrode according to Embodiments 15-17, wherein the surface irregularities of the first or second surface include one or more of the following: waves, notches, rounded hills and / or valleys, and grooves.

[0106] Embodiment 19: An anode electrode according to embodiments 15-18, wherein the second porous layer further comprises a third porous layer having a third surface opposite to the second surface and a fourth surface, and the fourth surface of the third porous layer and the third surface of the second porous layer form a second transport channel.

[0107] Embodiment 20: A battery comprising a pressure vessel and an electrode stack disposed within the pressure vessel, wherein the electrode stack holds an electrolyte membrane, and the electrode stack includes alternately stacked cathode electrodes and anode electrodes separated by a separator, the anode electrode includes one or more porous layers, each of the porous layers includes a porous substrate and a catalyst layer covering the porous substrate, the catalyst layer includes a transition metal, and at least one of the at least one porous layer includes a surface having characteristics that facilitate hydrogen gas transport.

[0108] Embodiment 21: A method for forming electrodes for a metal-metal hydride battery, comprising: obtaining one or more porous substrates; forming surface features on at least one surface of at least one of the porous substrates; coating the one or more porous substrates with a catalyst layer to form a porous layer; and connecting the porous layers to form the electrode.

[0109] Embodiment 22: The method of Embodiment 21, wherein coating one or more porous substrates with a catalyst layer includes electroplating the porous substrates with a catalyst layer, and the catalyst layer contains a transition metal alloy.

[0110] Embodiment 23: The method of Embodiments 21-22, wherein the porous substrate is electroplated with a catalyst layer in a tank containing two or more of Ni, Co, Cr, Mo, Fe, Zn, S, and W.

[0111] Embodiment 24: The method of embodiments 21-23, further comprising leaching a porous layer to remove some metals from the catalyst layer.

[0112] Embodiment 25: The method of Embodiments 21-24, wherein the transition metal alloy contains Mo, and the leaching includes removing Mo from a porous layer.

[0113] Embodiment 26: The method of Embodiments 21-25, wherein the leaching includes immersion of the porous layer in an alkaline solution containing KOH.

[0114] Embodiment 27: The method according to Embodiments 21-26, wherein the leaching is performed at a temperature higher than room temperature.

[0115] Embodiment 28: The method according to any one of Embodiments 21 to 27, wherein the temperature is approximately 40°C to approximately 80°C.

[0116] Embodiment 29: The method of Embodiments 21 to 28, further comprising an annealing step following a leaching step.

[0117] Embodiment 30: The method according to any one of Embodiments 21 to 29, wherein the annealing step comprises annealing in a furnace under a diluted hydrogen atmosphere at 100°C to 500°C.

[0118] Embodiment 31: The method of Embodiments 21-30, wherein forming surface features includes forming one of a wave, a notch, a rounded hill and / or valley, and a groove.

[0119] Embodiment 32: A method according to Embodiments 21 to 31, further comprising modifying at least one porosity of a porous substrate.

[0120] Embodiment 33: The method of Embodiments 21-32, further comprising coating at least one porous layer with a surface affinity modifying material to provide wet proofing.

[0121] Embodiment 34: The method of Embodiments 21-33, wherein connecting porous layers to form an electrode includes laminating a first porous layer and a second porous layer such that surface features form a first transport channel between the first porous layer and the second porous layer for the transport of hydrogen gas.

[0122] Embodiment 35: The method of Embodiments 21 to 34, further comprising further laminating a third porous layer with the second porous layer in order to form a second transport channel between the second porous layer and the third porous layer.

[0123] The foregoing descriptions in this disclosure are provided for illustrative and explanatory purposes only. They are not intended to be exhaustive or to limit the disclosure to any specific form disclosed. The breadth and scope of this disclosure should not be limited by any of the exemplary embodiments described above. Many modifications and variations will be apparent to those skilled in the art. Modifications and variations include any relevant combination of the disclosed features. The embodiments have been selected and described to best illustrate the principles of this disclosure and its practical application, thereby enabling other those skilled in the art to understand this disclosure for various embodiments, with various modifications suitable for the particular use intended. The scope of this disclosure is intended to be defined by the following claims and their equivalents.

Claims

1. an anode electrode for a metal-metal hydride battery, A plurality of porous layers, each of which comprises a porous substrate and a catalyst layer coated on the porous substrate, the catalyst layer comprising a binary functional catalyst, the catalyst layer comprising a transition metal, and the binary functional catalyst catalyzing both a hydrogen evolution reaction (HER) and a hydrogen oxidation reaction (HOR) at the anode electrode, the porous layer comprises At least one of the plurality of porous layers includes a surface contour that facilitates hydrogen gas transport through hydrogen gas transport channels formed between adjacent porous layers. Anode electrode.

2. The anode electrode according to claim 1, wherein the plurality of porous layers include a first surface of a first porous layer and a second surface of a second porous layer having the surface contour, and the first surface and the second surface form the hydrogen gas transport channel between the first porous layer and the second porous layer.

3. The anode electrode according to claim 1, wherein each of the plurality of porous layers comprises one or more of the following: metal or metal alloy foam, metal foil, metal mesh, fibrous conductive substrate, carbon fiber paper, carbon cloth, carbon felt, carbon mat, carbon nanotube film, graphite foil, graphite foam, graphite mat, graphene foil, graphene fiber, graphene film, and graphene foam.

4. The anode electrode according to claim 3, wherein the metal or metal alloy foam is one of nickel foam, nickel-molybdenum foam, nickel-iron foam, nickel-copper foam, nickel-cobalt foam, nickel-tungsten foam, nickel-silver foam, and nickel-molybdenum-cobalt foam.

5. The anode electrode according to claim 3, wherein each of the porous substrates of the plurality of porous layers comprises the metal or the metal alloy foam.

6. The anode electrode according to claim 1, wherein the binary functional catalyst is one or more of the following: nickel-molybdenum-cobalt (NiMoCo), nickel, nickel-molybdenum, nickel-tungsten, nickel-tungsten-cobalt, nickel-tungsten-copper, nickel-carbon, and nickel-chromium.

7. The anode electrode according to claim 1, wherein the transition metal of the binary functional catalyst includes two or more of Ni, Co, Cr, Mo, Fe, Zn, Sn, and W.

8. The anode electrode according to claim 1, wherein the binary functional catalyst comprises one or more of platinum, palladium, iridium, gold, rhodium, ruthenium, rhenium, osmium, silver, nickel, cobalt, manganese, iron, molybdenum, tungsten, and chromium.

9. The anode electrode according to claim 7, wherein the transition metal is a NiMoCo alloy or a NiMo alloy.

10. The anode electrode according to claim 1, wherein the plurality of porous layers include a first porous layer, a second porous layer, and a third porous layer disposed between the first porous layer and the second porous layer, and the third porous layer has a first surface contour different from the second surface contour of the first porous layer or the second porous layer.

11. The anode electrode according to claim 10, wherein the first surface contour includes one or more of a wave, a notch, a rounded hill and / or a valley, a groove.

12. The anode electrode according to claim 11, wherein at least one of the catalyst layers of the first porous layer, the second porous layer, and the third porous layer is at least partially coated with a moisture-resistant material.

13. The anode electrode according to claim 12, wherein the moisture-resistant material comprises one of polyethylene, polypropylene, partially or fully fluorinated polymer, polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), polyethylene tetrafluoroethylene (ETFE), polyvinyl fluoride (PVF), and fluorinated polyvinylidene (PVDF).

14. The plurality of porous layers are A first porous layer having a first surface; A second porous layer having a second surface and adjacent to the first porous layer; Equipped with, The first surface of the first porous layer and the second surface of the second porous layer include a surface contour that forms a hydrogen gas transport channel. The anode electrode according to claim 1.

15. The anode electrode according to claim 14, wherein the first surface is flat or smooth, and the second surface includes an uneven shape.

16. The anode electrode according to claim 14, wherein one or both of the first surface and the second surface include an uneven shape.

17. The anode electrode according to claim 16, wherein the uneven shape of the first or second surface includes one or more of the following: waves, notches, rounded hills and / or valleys, grooves.

18. The aforementioned second porous layer has a third surface opposite to the aforementioned second surface, The anode electrode further comprises a third porous layer having a fourth surface, The fourth surface of the third porous layer and the third surface of the second porous layer form a second transport channel. The anode electrode according to claim 14.

19. pressure vessel; An electrode stack disposed within the pressure vessel and holding an electrolyte; Equipped with, The electrode stack comprises cathode electrodes and anode electrodes that are separated by a separator and stacked alternately, the anode electrode comprises a plurality of porous layers, each porous layer comprises a porous substrate and a catalyst layer coated on the porous substrate, the catalyst layer comprises a binary functional catalyst, the catalyst layer comprises a transition metal, and the binary functional catalyst catalyzes both the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR) at the anode electrode. At least one of the plurality of porous layers includes a surface contour that facilitates hydrogen gas transport through hydrogen gas transport channels formed between adjacent porous layers. Metal-hydrogen battery.

20. A method for forming an anode electrode for a metal-hydrogen cell, Steps to obtain multiple porous substrates; A step of forming a surface contour on at least one surface of the plurality of porous substrates that facilitates hydrogen gas transport through hydrogen gas transport channels; The steps include: coating the plurality of porous substrates with a catalyst layer containing a binary functional catalyst to form a porous layer, wherein the binary functional catalyst catalyzes both the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR) at the anode electrode; A step of forming the anode electrode by stacking and connecting the porous layers to each other, thereby forming the hydrogen gas transport channel between adjacent porous layers; A method of having.

21. The method according to claim 20, wherein the step of coating one or more porous substrates with the catalyst layer includes the step of electroplating the porous substrates with the catalyst layer, and the catalyst layer comprises a transition metal alloy.

22. The method according to claim 21, wherein the step of electroplating the porous substrate with the catalyst layer is carried out in a tank containing two or more of Ni, Co, Cr, Mo, Fe, Zn, Sn, and W.

23. The method according to claim 21, further comprising the step of leaching the porous layer to remove some metals from the catalyst layer.

24. The method according to claim 23, wherein the transition metal alloy contains Mo, and the leaching comprises removing Mo from the porous layer.

25. The method according to claim 23, wherein the leaching comprises immersing the porous layer in an alkaline solution containing KOH.

26. The method according to claim 25, wherein the leaching is carried out at a temperature higher than 30°C and lower than 100°C.

27. The method according to claim 26, wherein the temperature is 40°C to 80°C.

28. The method according to claim 23, further comprising an annealing step after the leaching.

29. The method according to claim 28, wherein the annealing step comprises annealing in a furnace at a temperature between 100°C and 500°C under a dilute hydrogen atmosphere.

30. The method according to claim 20, wherein the step of forming a surface contour includes forming one of a wave, a notch, a rounded hill and / or a valley, or a groove.

31. The method according to claim 20, further comprising the step of changing the porosity of at least one of the porous substrates.

32. The method according to claim 20, further comprising the step of coating at least one of the porous layers with a surface affinity modifying material to provide moisture resistance.

33. The method according to claim 20, wherein the step of connecting the porous layers to form the electrode includes stacking the first porous layer and the second porous layer so that the surface contour forms a first transport channel for transporting hydrogen gas between the first porous layer and the second porous layer.

34. The method according to claim 33, further comprising the step of laminating a third porous layer with the second porous layer to form a second transport channel between the second porous layer and the third porous layer.