JP2024524278A - Electrode for metal hydride battery and method for producing same - Google Patents

Abstract

An electrode for a metal-hydrogen battery is described. The electrode includes one or more porous layers, each of the porous layers including a porous substrate and a catalytic layer overlying the porous substrate, the catalytic layer including a transition metal, and at least one of the at least one porous layer including a surface having characteristics that facilitate 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

Related Applications
This application claims priority to and the benefit of U.S. Patent Application No. 17/847,591, filed June 23, 2022, which claims priority to and the benefit of U.S. Provisional Patent Application No. 63/214,514, filed June 24, 2021, both of which are incorporated by reference in their entireties herein.

The present disclosure relates generally to metal hydrogen batteries and methods for manufacturing those batteries, and more particularly to anode electrodes used in metal hydrogen batteries and methods for manufacturing the anode electrodes.

For renewable energy resources such as wind and solar to compete with traditional fossil fuels, large-scale energy storage systems are needed to mitigate their inherent intermittency. To build large-scale energy storage, cost and long lifespan are the biggest considerations. Currently, pumped hydropower dominates the grid energy storage market as it is a cheap way to store large amounts of energy for long periods of time (approximately 50 years), but is constrained by lacking suitable locations and environmental footprint. Other technologies such as compressed air and flywheel energy storage exhibit some distinct 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.

Described herein are electrodes for metal-hydrogen batteries, as well as methods for making the electrodes and batteries. In some embodiments, an electrode for a metal-hydrogen battery includes one or more porous layers, each of which includes a porous substrate and a catalyst layer overlying the porous substrate, the catalyst layer including a transition metal, and at least one of the porous layers includes a surface having characteristics that facilitate hydrogen gas transport. In some embodiments, an 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 a transport channel.

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 a transport channel.

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

In some embodiments, a method for forming an electrode for a metal-hydrogen battery includes 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 an electrode.

Other embodiments are contemplated and are described herein below.

Particular features of various embodiments of the present technology are set forth in detail in the appended claims. A better understanding of the features and advantages of the present technology will be obtained by reference to the following detailed description that sets forth illustrative embodiments in which the principles of the present disclosure are utilized and the accompanying drawings, in which:

1 shows a schematic diagram of a metal-hydrogen battery that can include embodiments of electrodes according to the present disclosure. 1 shows a schematic diagram of a metal-hydrogen battery that can include embodiments of electrodes according to the present disclosure. 1 shows a schematic diagram of a metal-hydrogen battery that can include embodiments of electrodes according to the present disclosure.

1 shows a cross-sectional view of an electrode having a single layer structure according to some embodiments of the present disclosure.

1 illustrates a cross-sectional view of an electrode having a dual-layer structure according to some embodiments of the present disclosure.

1 illustrates a cross-sectional view of an electrode having another bi-layer structure according to some embodiments of the present disclosure.

1 shows a cross-sectional view of an electrode having a three-layer structure according to some embodiments of the present disclosure.

1 shows a porous substrate coated with a catalyst layer according to some embodiments of the present disclosure.

1 illustrates a method of forming an electrode for a metal-hydrogen battery according to some embodiments of the present disclosure.

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

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

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

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

10A-D are scanning electron microscope (SEM) images showing that the surface of an electrode with a higher double layer capacitance (C _dl ), according to some embodiments, has a rougher surface.

1 illustrates the consistent catalyst loading achieved by using a plating bath with a higher metal concentration according to some embodiments of the present disclosure.

FIG. 1 illustrates capacity versus voltage curves for three battery cells formed with electrodes according to some embodiments of the present disclosure.

FIG. 2 illustrates efficiency versus cycle number curves for three battery cells according to an exemplary embodiment.

1 is an image of a porous layer exhibiting wavy surface features according to some embodiments of the present disclosure.

1 is a SEM image showing a porous substrate prior to a compression process according to some embodiments of the present disclosure.

1 is a SEM image showing a porous substrate after compression according to some embodiments of the present disclosure.

FIG. 2 shows the voltage-capacity curves of a 10 Ah battery using a tri-layer electrode according to some embodiments of the present disclosure.

FIG. 1 illustrates a battery cell having electrodes that are not coated with a surface affinity modification (e.g., a wet-proofing coating), according to some embodiments.

FIG. 13B shows that the battery cell after the wetproof coating step according to some embodiments of the present disclosure exhibits significantly improved discharge characteristics over the discharge characteristics of the battery cell shown in FIG. 13A.

1 illustrates stable cycling of a battery having electrodes according to some embodiments.

1 shows voltage versus capacity for batteries cycled over a wide range of charge rates (C-rates) using electrodes according to some embodiments.

1 illustrates the long-term cycling performance of another battery having an electrode according to some embodiments.

In the following description, certain specific details are set forth to provide a thorough understanding of various embodiments of the present disclosure. However, those skilled in the art will understand that the present disclosure may be practiced without these details. Moreover, while various embodiments of the present disclosure are disclosed herein, many adaptations and modifications can be made within the scope of the present disclosure in accordance with the common general knowledge of those skilled in the art. Such modifications include the substitution of known equivalents for any aspect of the present disclosure to achieve the same result in substantially the same way.

Unless the context otherwise requires, throughout this specification and the claims, the word "comprises" and variations thereof, such as "comprises" and "comprising," are to be interpreted in their open, inclusive sense as "including," which is to be interpreted as "including, but not limited to." The recitation of numerical ranges throughout the specification is intended to serve as a shorthand notation for referencing each separate value falling within the range, including the values defining the range, and each separate value is incorporated in the specification as if it were individually set forth herein. In addition, the singular forms "a," "an," and "said" include plural referents unless the context clearly dictates otherwise.

Throughout this specification, a reference to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment, but may be any example. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

Embodiments of the present disclosure describe electrodes for metal-hydrogen batteries formed from 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 including a transition metal. At least one of the one or more porous layers includes a surface having characteristics that facilitate 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.

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

1A, the electrode stack assembly 130 can be housed in a pressure vessel 109. As shown, the electrolyte membrane 108 is placed in the pressure vessel 109 such that the stack 130 is saturated with the electrolyte membrane 108. The cathode electrode 102, the anode electrode 104, and the separator 106 are porous, which retains the electrolyte membrane 108 and allows 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, so long as the cathode electrode 102 and the anode electrode 104 are electrically insulated from each other and sufficient electrolyte membrane 108 is retained in the electrode stack 130. For example, the space occupied by the separator 106 may be filled with the electrolyte membrane 108.

The metal-hydrogen battery 100 shown in FIG. 1A can further include a fill tube 122 configured to introduce electrolyte or gas (e.g., hydrogen) to the pressure vessel 109. The fill tube 122 can include one or more valves (not shown) for controlling flow into and out of the pressure vessel 109 enclosure, or the fill tube 122 can be otherwise sealable after filling the pressure vessel 109 with the electrolyte membrane 108 and hydrogen gas.

As shown in FIG. 1A and discussed above, the electrode stack assembly 130 has several stacks of alternating cathode electrodes 102 and anode electrodes 104 separated by separators 106. The electrodes in the electrode stack assembly 130 can be coupled in parallel or in series, although in the example battery 100 shown in FIG. 1A the electrodes are coupled in parallel. In particular, each of the cathode electrodes 102 is coupled to a conductor 118 and each of the anode electrodes 104 is coupled to a conductor 116. Although FIG. 1A shows the fill tube 122 disposed on the side of the conductor 118, the fill tube 122 may alternatively be disposed on the side of the conductor 116 or may be disposed elsewhere in the pressure vessel 102.

As further shown in FIG. 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. The terminal 120 can have a feedthrough that allows the terminal 120 to extend outside the pressure vessel 102, or the conductor 116 can be directly connected to the pressure vessel 109, particularly since the terminal 120 is coupled to the anode electrode 104. Similarly, the conductor 118 coupled to the cathode electrode 102 can be coupled to a feedthrough terminal 124 that represents the opposite (positive) terminal of the battery 100. Since the terminal 124 is coupled to the cathode electrode 104, the terminal 124 passes through an insulated feedthrough that allows the terminal 124 to extend outside the pressure vessel 109.

As shown in FIG. 1A, the electrode stack 104 can be secured within a frame 132. In FIG. 1A, the electrode stack assembly 130 can be configured to have an anode electrode 104 on each side adjacent to the frame 132 to isolate the cathode electrode 102 from the frame 132. In some embodiments, a separator 106 can be included adjacent to the frame 132 for further isolation, particularly when the electrode stack assembly 130 is positioned such that the cathode electrode 102 is adjacent to the frame 132 rather than the anode electrode 104.

As described above, the electrode stack 130 has alternating layers of cathode electrodes 102 and anode electrodes 104 separated by separators 106. The electrode stack assembly 130 is disposed within a pressure vessel 109 and includes an electrolyte membrane 108, in which ions can migrate between the cathode electrodes 102 and the 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.

1B shows some embodiments of the cathode electrode 102. The cathode electrode 102 can 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 can be a redox reactive material including a transition metal, as discussed further below. Similarly, as shown in FIG. 1C, the anode electrode 104 can have one or more anode porous layers 142, each of which includes a porous conductive substrate 110 coated with a catalyst layer 112. Thus, as shown in FIG. 1B, the cathode electrode 102 can be formed from one or more cathode porous layers 140. As shown in FIG. 1C, the anode electrode 104 can be formed from one or more anode porous layers 142.

In some embodiments, the anode electrode 104 is a catalytic hydrogen electrode. As shown in FIG. 1C, in some embodiments, the anode electrode 104 has a stack of porous layers 142, each of which includes a porous conductive substrate 110 and a catalyst layer 112 overlying the porous conductive substrate 110. The catalyst layer 112 can 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, steel foam, etc. 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 be formed from other conductive substrates, such as metal foils, metal meshes, or fibrous conductive substrates. In some embodiments, the conductive substrate 110 can be formed from carbon-based materials, such as carbon fiber paper, carbon cloth, carbon felt, carbon mats, carbon nanotube films, graphite foils, graphite foams, graphite mats, graphene foils, graphene fibers, graphene films, or graphene foams.

In some embodiments, the bifunctional catalyst of the catalyst layer 112 may be a nickel-molybdenum-cobalt (NiMoCo) alloy. Other transition metals or metal alloys may be bifunctional catalysts, such as nickel, nickel-molybdenum, nickel-tungsten, nickel-tungsten-cobalt, nickel-tungsten-copper, nickel-carbon, nickel-chromium, and other composites based on the transition metals. In some embodiments, the bifunctional catalyst of the catalyst layer 112 may have a transition metal alloy including two or more of Ni, Co, Cr, Mo, Fe, Mn, Cu, Zn, Sn, and W. Other precious metals and their alloys, such as platinum, palladium, iridium, gold, rhodium, ruthenium, rhenium, osmium, silver, and alloys thereof with non-precious transition metals, such as platinum, palladium, iridium, gold, rhodium, ruthenium, rhenium, osmium, silver, nickel, cobalt, manganese, iron, molybdenum, tungsten, chromium, and the like. In some embodiments, the bifunctional catalyst of the catalyst layer 112 can be a combination of a HER catalyst and a HOR catalyst. In some embodiments, the bifunctional catalyst of the catalyst layer 112 can include a mixture of different materials, such as transition metals and their oxides/hydroxides, that collectively contribute to the hydrogen evolution and oxidation reactions. In some embodiments, the catalyst layer 112 includes bifunctional catalyst nanostructures having a size (or average size) ranging from about 1 nm to about 100 nm, from about 1 nm to about 80 nm, or from about 1 nm to about 50 nm, for example. In some embodiments, the catalyst layer 112 includes a bifunctional catalyst microstructure having a size (or average size) in the range of, for example, about 100 nm to about 500 nm, about 500 nm to about 1000 nm.

In some embodiments, the anode electrode 104 may be a single layer or a multi-layer structure, as described above in FIG. 1C. In some embodiments, the anode electrode 104 may be formed with a flat or uneven surface, or may be formed with multiple layers with a combination of flat and uneven peripheral surfaces. An embodiment of the present disclosure includes at least one porous layer 142 having a surface with characteristics that result in an uneven surface.

FIG. 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 a textured 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 textured surfaces 302a and 302b can increase 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 textured surfaces 302a, 302b can be symmetrical or asymmetrical. In some embodiments, the textured surfaces 302a and 302b of the single-layer structure 302 can be formed by pressing or stamping a rectangular solid substrate against the electrode porous substrate 110 to create the desired surface contour. In some embodiments, the features of the surface 302a can include, for example, a corrugated surface. In some embodiments, the features of the surface 302b may be smooth or flat, or may be corrugated. The formation of features on the surfaces 302a and 302b may be accomplished prior to application of the catalytic coating 112, or in some embodiments, after the catalytic coating 112. As shown in FIG. 2, according to one exemplary embodiment, the features of the textured surfaces 302a and 302b may be corrugated. Other surface contour features may also be formed. For example, the surfaces 302a and 302b may include rounded hills and/or valleys, notches, corrugations, or other features. In some embodiments, one of the surfaces 302a and 302b may be configured to be flat or smooth. As described below with respect to FIG. 2, the single layer structure 302 may include a porous substrate 110 formed of a metal or metal alloy foam. The surface contour (e.g., a corrugated surface or other characteristic surface) of the single layer structure 302 of FIG. 2 is shown in a macroscopic view. In a microscopic view, the surface of the single layer structure 302 includes a plurality of micropores and/or nanopores.

Some embodiments of the anode electrode 104 include any number (one or more) of porous layers 142, with at least one porous layer 142 including a surface with non-uniform features. These non-uniform features can be formed by pressing or stamping the porous conductor 110 of that porous layer 142. The non-uniform surface can include features such as corrugations, rounded hills, notches, grooves, or other shapes that make the surface topology non-uniform. Figures 3A-3C show some embodiments of the anode electrode 104. However, it should be understood that any stack of porous layers 142 that form channels that facilitate the flow of hydrogen gas can be used. For example, Figure 2 shows a single layer anode electrode 104 with a corrugated surface, for example. Figure 3A shows an embodiment of the anode electrode 104 with two porous layers 142, Figure 3B shows another embodiment of the anode electrode 104 with two porous layers 142, and Figure 3C shows an embodiment of the anode electrode 104 with three porous layers 142. However, embodiments of the anode electrode layer 104 can also include three or more layers.

3A shows a cross-sectional view of an anode electrode 104 having a bi-layer structure 304 (i.e., two porous layers 142) according to some embodiments. The bi-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 FIG. 2 and includes a non-uniformly characterized upper surface 306a and a 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 the surfaces 306a and 308a depending on the features formed on the surface 306a of the porous layer 306. For example, the corrugated porous layer 306 forms the channels 310. The channels 310 can be formed to have other features similar to those described above. As discussed above, the channels 310 can facilitate the movement of hydrogen gas through the HOR and HER. In some embodiments, the porosity of the first and second porous layers 306, 308 may also differ. As described below with respect to FIG. 4, each of the first and second layers 306, 308 may include a porous substrate 110 (e.g., a metal or alloy foam) coated with a catalyst layer 112. The flat or uneven surfaces of the first and second layers 306, 308 in FIG. 3A are shown in a macroscopic view. In a microscopic view, the surfaces include a plurality of micropores and/or nanopores.

In some embodiments, the channels may also be created by stacking two porous layers 142, each with non-uniform surface features between the different layers. An embodiment of an anode electrode 104 illustrating this embodiment is shown in FIG. 3B. FIG. 3B shows a cross-sectional view of an anode electrode 104 having a bi-layer structure 311 (two porous layers 142), according to some embodiments. The bi-layer structure 311 includes a first porous layer 312 and a second porous layer 314 stacked adjacent to each other. As shown in FIG. 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 FIG. 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 include non-uniform features or 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 the 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 respect to FIG. 4, each of the first porous layer 312 and the second porous layer 314 can include a porous substrate 110 (e.g., a metal or metal alloy foam) and a catalyst layer 112 covering the porous substrate 110. The textured surfaces of the first porous layer 312 and the second porous layer 314 shown in FIG. 3B are shown macroscopically. At a microscopic view, the surfaces include a plurality of micropores and/or nanopores.

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 some 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 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 porosity and the second porosity.

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 during HOR and HER. In the illustrated embodiment shown in FIG. 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 the surface 322a is configured to be uneven (e.g., corrugated, notched, rounded hills and/or valleys, grooves, or other features) such that at least one channel 310 is formed therebetween. Additionally, 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 the surface 324a is configured to be uneven (e.g., corrugated, notched, or including other such features) such that at least one channel 310 is formed therebetween.

It should be understood that the embodiments shown in FIG. 2 and FIG. 3A-3C are merely exemplary and not limiting. Other configurations are contemplated. For example, each of the embodiments shown in FIG. 2 and FIG. 3A-3C may include an additional porous layer 142. Additionally, although surfaces 326a and 326b are shown as corrugated, other surface contours may be used if the surface contours can facilitate the generation of gas channels at the interface. In some embodiments, at least one of surfaces 322a and 326a is non-uniform such that at least one gas channel can be generated therebetween, and/or at least one of surfaces 324a and 326b is non-uniform such that at least one gas channel can be generated therebetween. In some embodiments, the contours of surfaces 322a and 326a are configured differently from one another such that at least one gas channel can be generated therebetween, and/or the contours of surfaces 324a and 326b are configured differently from one another such that at least one gas channel can be generated therebetween. Also, although the anode electrode 104 is illustrated as having three porous layers, the disclosure is not limited to this structure. For example, the anode electrode 104 can include a top 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 top and bottom stacks. In some embodiments, a gas diffusion layer can be disposed between the first porous layer 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 can be porous.

In some embodiments, the first porous layer 322 and the second porous layer 324 can be configured to have an uneven (e.g., corrugated, notched, or other feature-containing) surface similar to the surfaces 326a and 326b of the third porous layer 326. The corrugated surfaces of two adjacent layers are positioned opposite each other, thereby forming the 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.

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

Referring to FIG. 4, in some embodiments, each of the first porous layers 142 (or layer structures shown in FIGS. 2, 3A, and 3B) includes a porous substrate 410 and a catalyst layer 412 coated on the porous substrate 410, the catalyst layer 412 including a transition metal alloy. The porous substrate 410 is similar to the porous conductive substrate 110 of FIG. 1C and may include a metal foam or a metal alloy foam, as described above. The catalyst layer 412 is similar to the catalyst layer 112 of FIG. 1C. Thus, the surface profiles of FIGS. 2 and 3A-3C are shown in macroscopic view. Each of these surfaces includes a plurality of micropores and/or nanopores 414, as shown in FIG. 4.

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

1B, the cathode electrode 102 can include a conductive substrate 114 and a coating 116 covering the conductive substrate 114. The coating 116 includes a redox-reactive material including a transition metal. In some embodiments, the conductive substrate 114 is porous, e.g., having 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. In some embodiments, the conductive substrate 114 can 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 encompassed by the present disclosure. In some embodiments, the transition metal included in the redox-reactive material is nickel. In some embodiments, the nickel is included as, for example, nickel hydroxide or nickel oxyhydroxide. In some embodiments, the transition metal included in the redox-reactive material can be cobalt. In some embodiments, the 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 or post-transition metals). Other transition metals, such as silver, are also encompassed by the present disclosure. In some embodiments, the coating microstructure of the redox-reactive material may have a size (or average size) ranging from about 1 μm to about 100 μm, from about 1 μm to about 50 μm, or from about 1 μm to about 10 μm, for example.

In some embodiments, the electrolyte membrane 108 is an aqueous electrolyte. Aqueous electrolytes are alkaline and have a pH greater than 7, e.g., about 7.5 or greater, about 8 or greater, about 8.5 or greater, about 9 or greater, about 11 or greater, or about 13 or greater. As non-limiting examples, the electrolyte membrane 108 may include KOH or NaOH or LiOH, or a mixture of LiOH, NaOH, and/or KOH.

Figure 5 illustrates an embodiment of a method 500 for forming an embodiment of an 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 substrate 110 may be electrically conductive, as described above. In some embodiments, metal foams such as nickel foam, copper foam, iron foam, steel foam, aluminum foam, etc. may be employed to form the porous substrate 110. In some embodiments, the porous substrate 110 is a metal alloy foam including nickel, such as nickel-iron foam, nickel-molybdenum foam, nickel-copper foam, nickel-cobalt foam, nickel-tungsten foam, nickel-silver foam, nickel-molybdenum-cobalt foam, etc. As described above, the porous substrate 110 may also be formed from other materials, such as porous metal foils, metal meshes, and fibrous conductive substrates. Additionally, 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.

In step 504, the porous substrate 110 may be modified. Modification of the porous substrate 110 may be accomplished in a number of 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 steps that may be performed in the modification step 504 are described further below. Also, if there are multiple porous substrates 110 being processed, the treatments performed for each individual porous substrate 110 in the modification step 504 may be different from each other.

In step 506, each of the porous substrates prepared in the modification step 504 is coated with a catalyst layer 112, for example by electrolytic plating. The catalyst layer 112 can include two or more transition metals, such as Ni, Co, Cr, Mo, Fe, Zn, Sn, and W. In some embodiments, the catalyst layer 112 includes 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 implementations, the catalyst layer 112 may not cover the entire surface of the porous substrate 110. In the electrolytic plating process, electrolytic plating can be performed in a bath containing a transition metal to form the catalyst layer. In some embodiments, the plating bath can be a solution of salts of nickel, molybdenum, cobalt, etc., having a concentration in the range of 0.1 to 100 g/liter (grams per liter). The plating bath solution may also have pH buffer salts, such as sodium bicarbonate, having a concentration ranging from 1 to 100 g/L, and possibly other salts, such as sodium pyrophosphate, having a concentration ranging from 1 to 100 g/L, to help stabilize the plating bath solution.

Deposition of the catalyst layer 112 in step 506 can also be performed via chemical reduction or physical vapor deposition (PVD) methods such as sputtering, e-beam deposition, or chemical vapor deposition (CVD), atomic layer deposition (ALD), or other methods. Additionally, as described above, the catalyst can be a dual-function catalyst as described above.

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

In step 510, one or more porous layers 142, each coated with a catalyst layer resulting from step 508, are connected/bonded together to form an anode electrode 104 for the metal-hydrogen battery 100. The resulting anode electrode 104 may be as 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 have been subjected to different processing in method 508.

It should be further understood that although operations 502-510 are shown in a particular sequence in FIG. 5, the disclosure is not so limited. Operations 502-510 may be performed in different orders to form the same or similar electrodes. FIG. 5 is for illustrative purposes and is not intended to be limiting with respect to the order of operations.

FIGS. 6-9 show various embodiments of the method 500. Although FIGS. 6-9 illustrate various individual processes, it should be understood that the method 500 used to manufacture a particular embodiment of the anode electrode 104 may include any combination or all of the processes discussed herein.

FIG. 6 shows a method 600, which is an example of a method 500 for forming an anode electrode 104 for a metal-hydrogen battery 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 substrate 110 is coated with a catalyst layer 112, for example by electrolytic plating, to form a porous layer 142. In step 508, the porous layer 142 undergoes further processing. In this embodiment of the method 600, the processing step 508 can include a metal leaching process 602 to remove some of the metal from the catalyst layer 112 of the porous layer 142. In some embodiments, an annealing step 604 can be performed after the metal leaching process 602 during the processing step 508. In step 510, one or more porous layers 142 formed of a porous substrate 110 each coated with a catalyst layer 112 are connected/bonded together to form an anode electrode 104 for the metal-hydrogen battery 100.

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., KOH solution) to selectively leach some metals from the catalyst layer 112. This procedure results in a high surface area with a high density of active HOR/HER sites per unit area. In some embodiments, the leaching may be performed 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, to accelerate the leaching process. 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. The leaching of metals is not limited to high pH plating solutions, but can be performed with plating solutions over the entire pH range (0-14) according to the solubility of the target metals. For example, Ni can be leached in an acidic solution (pH<7) to increase the surface area. The leaching bath can also include an oxidizing or reducing agent to promote metal dissolution from the pure metal or alloy. As further shown in FIG. 6, in some embodiments, the leaching step 602 can be followed by an annealing step 604, in which the porous layer is sent to an oven and annealed in a dilute hydrogen atmosphere to deoxidize the surface. The annealing can be performed at a similar temperature to the leaching step (e.g., at a temperature of 100° C. or higher). In some embodiments, the annealing step 604 can be performed in a dilute atmosphere at 100° C. to 500° C., e.g., 400° C.

Figure 7 shows a method 700, which is another embodiment of the method 500 for forming an anode electrode 104 for a metal-hydrogen battery 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, the porosity of at least some of the porous substrates 110 is altered in step 702. In step 506, the porous substrate 110 is coated with a catalyst layer 112, for example, by electroplating as described above. 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 of the one or more porous layers 142 formed respectively from the porous substrates 110 coated in the catalyst layer 112 are connected/bonded to each other to form an anode electrode 104 for a metal-hydrogen battery 100 as described above.

Step 702 of the processing step 504 can, in some embodiments, reduce the porosity of one or more of the porous substrates 110, for example, by compressing the porous support 110. For example, one or more of the 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 a more rigid porous substrate 110 for forming the anode electrode 104. In some embodiments, the porous substrate 110 can 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 at the outermost of the anode electrode 104 can 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 inner porous substrate 110 may or may not undergo a compression process in step 702. This configuration involves higher compression in the outer porous layer 142 than in the inner porous layer, creating stiffness on the outside of the anode electrode 104 and providing high porosity on the inside of the anode electrode 104 to facilitate fluid or gas flow for the HER and HOR.

Figure 8 shows a method 800, which is another embodiment of the method 500 for forming an anode electrode 104 for a metal-hydrogen battery 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, the surface morphology of at least some of the porous substrates 110 is 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 formed respectively from the porous substrates 110 coated in the catalyst layer 112 are connected/bonded to each other to form an anode electrode 104 for a metal-hydrogen battery 100 as described above.

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., channel 310 in FIG. 3A-3C) are formed at the interface of two adjacent porous layers 142. For example, one or more porous substrates 110 may be punched on their surfaces to generate different surface morphologies, for example, for two adjacent surfaces of two adjacent porous substrates 110. For example, one of the two adjacent surfaces is configured to be rough/uneven, while another of the two adjacent surfaces is configured to be smooth/flat. The surface of the porous substrate 110 may be any of a variety of shapes, such as, for example, corrugated, alternating concaves and convexes, spikes, 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 morphology 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 as well as the adjustment of the porosity of the porous substrate 110.

9 shows a method 900, which is another embodiment of the method 500 for forming an anode electrode 104 for a metal-hydrogen battery 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 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 shown in FIG. 9, step 508 can include a surface affinity coating step 902, as described further below. As described above, in step 510, one or more porous layers 142 formed respectively from the porous substrates 110 coated in the catalyst layer 112 are connected/bonded to each other to form an anode electrode 104 for a metal-hydrogen battery 100 as described above. In step 902 of step 508, a surface affinity modifying material is coated onto the catalyst layer.

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

It should be understood that the methods disclosed herein may be modified or combined, in part or in whole, to render an electrode suitable for use in a metal-hydrogen battery. Specifically, the method 500 may include any combination of processes as discussed in each of Figures 6-9. Specific examples are provided below to illustrate further methods of forming an anode electrode 104 for a metal-hydrogen battery 100.

Example I: Increasing Active HOR/HER Sites on the Surface of the Electrode In some embodiments, the catalytic layer 112 can be formed in step 506 using electrodeposition of NiMoCo alloy onto the porous electrode 110. In these embodiments, the resulting porous layer 142, along with the porous substrate 110 and catalytic layer 112, can be immersed in a concentrated KOH solution to selectively leach out some of the Mo in step 602 as shown in FIG. 6. This process can result in a high surface area with a high density of active HOR/HER sites per unit area. A robust electrochemical impedance process was developed to estimate the surface area from the double layer capacitance (C _dl ), which can be further evaluated using electron microscopy. FIGS. 10A-10D are scanning electron microscope (SEM) images showing that surfaces with higher C _dl have rougher surfaces. C _dl correlates very strongly with the HOR/HER charge transfer resistance (Rct) and can be used to quickly screen the quality of a batch of porous layers.

Example II: Electroplating Bath Composition The bath composition that can be used to electroplate the catalyst in step 506 can be modified by increasing the metal ion concentration by 2-5 times. Such an increase in metal ion concentration increases the catalyst loading and performance. A higher metal concentration of metal ions can be used for many plating runs performed before the bath needs to be refilled. FIG. 11A shows the mass loading in mg/ ^cm2 versus batch number, illustrating the consistent catalyst loading achieved by the increased metal concentration without the need to frequently refill the bath. Battery cells made using this redesigned bath also showed strong performance. FIG. 11B shows a graph of voltage versus capacity for several cells (cells 1, 2, and 3) each formed with a pair of cathode and anode electrodes 102 and 104 formed according to an embodiment of the present disclosure. FIG. 11C shows the efficiency and capacity versus cycle number for the three cells shown in FIG. 11B. FIGS. 11B and 11C show strong performance using the proposed bath composition.

Example III: Mo leaching from NiMoCo catalyst The Mo leaching process step 602 described above can be performed on the porous substrate 110 in concentrated KOH on the porous layer after electrolytic plating of the porous layer of the NiMoCo catalyst layer 112 to increase the active reaction sites on the surface area. The leaching process step 602 takes longer at room temperature than if performed at elevated temperatures. 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 elevated temperatures for a short period of time, for example as little as 30 minutes.

Example IV: Three-Layer Electrode Structure The three-layer anode structure, as shown in FIG. 3C above, allows for high density of catalytic sites and easy hydrogen gas transport without the need for a gas screen. As described above, the anode electrode 104 includes three porous layers (layers 322, 324, and 326) stacked together. The hydrogen flow channels are formed by corrugating the middle layer 326 of the three porous substrates. FIG. 12A is an image showing an example of a corrugated middle layer, layer 326. FIG. 12B is an SEM image showing the porous substrate before compression in the porosity modification step 702 of FIG. 7; FIG. 12C is an SEM image showing the porous substrate 110 after compression in the porosity modification step 702 of FIG. 7. FIG. 12C also shows that the compressed porous substrate has low porosity. FIG. 12D shows the voltage-capacity curve of a 10 Ah battery using a tri-layer anode electrode 104 as shown in FIG. 3C, demonstrating the strong performance when using a tri-layer anode electrode 104.

Example V: Wet-Proof Anode Using PTFE By performing affinity coating step 902 of processing step 508 as shown in FIG. 9 using a dipping and sintering process, hydrophobic sites on the anode porous layer 142 can be induced to create an optimal balance between electrolyte permeation and hydrogen gas transport without causing anode flooding. FIG. 13A is a voltage vs. capacity diagram showing that a battery cell without a wet-waterproof (affinity) coating is difficult to discharge due to anode flooding. The resulting battery is difficult to discharge due to anode flooding by the electrolyte membrane 108, which inhibits the HOR reaction by blocking hydrogen gas access to the electrode surface. FIG. 13B is a voltage vs. capacity diagram showing that a battery cell in which the anode porous layer 142 includes a moisture-resistant coating (e.g., fluoropolymer) exhibits significantly improved discharge characteristics over the discharge characteristics of the battery cell shown in FIG. 13A.

Example VI: Stable Battery Performance at High Temperature 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 at a charge rate of 0.5C at 45°C for more than 3000 cycles with stable performance.

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

Example VIII: Stable 2C cycling performance at room temperature FIG. 16 shows a 20 Ah cell having a bi-layer structure anode electrode 104 as shown in FIG. 3A, which can be cycled at charge rates of 2C or higher for over 1000 cycles with stable cell performance.

Aspects of the Disclosure Aspects of the disclosure describe electrodes incorporating metal hydride batteries and the formation thereof. A selection of numerous aspects of the disclosure can include the following aspects:

Aspect 1: An electrode for a metal-hydrogen battery, the electrode comprising one or more porous layers, each of the porous layers comprising a porous substrate and a catalyst layer overlying 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.

Aspect 2: The electrode of aspect 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.

Aspect 3: The electrode of aspects 1-2, wherein the porous substrate of each of the at least one porous layer comprises one or more of a metal or metal alloy foam, a metal foil, a metal mesh, a fibrous conductive substrate, a carbon fiber paper, a carbon cloth, a carbon felt, a carbon mat, a carbon nanotube film, a graphite foil, a graphite foam, a graphite mat, a graphene foil, a graphene fiber, a graphene film, and a graphene foam.

Aspect 4: The electrode of aspects 1-3, 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.

Aspect 5: The electrode of aspects 1-4, wherein the porous substrate of each of at least one of the porous layers comprises a metal foam or a metal alloy foam.

Aspect 6: An electrode according to aspects 1 to 5, wherein the catalyst layer is a bifunctional catalyst that contributes to both the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR).

Aspect 7: The electrode of aspects 1 to 6, wherein the bifunctional 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.

Aspect 8: An electrode according to aspects 1 to 7, wherein the transition metal of the bifunctional catalyst comprises two or more of Ni, Co, Cr, Mo, Fe, Zn, Sn, and W.

Aspect 9: The electrode of aspects 1-8, 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.

Aspect 10: The electrode of aspects 1 to 9, in which the transition metal alloy is a NiMoCo alloy or a NiMo alloy.

Aspect 11: The electrode of aspects 1-10, wherein at least one porous layer includes a first porous layer, a second porous layer, and a third porous layer disposed between the first and second porous layers, and the third porous layer has a first surface contour that is different from the second surface contour of the first or second porous layers.

Aspect 12: The electrode of aspects 1-11, wherein the features include one or more of corrugations, notches, rounded hills and/or valleys, and grooves.

Aspect 13: The electrode of aspects 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 coated with a moisture-proof material.

Aspect 14: The electrode of aspects 1-13, wherein the wet proofing material comprises one of polyethylene terephthalate, polypropylene, a partially or fully fluorinated polymer, polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEB), polyethylene terephthalate tetrafluoroethylene (ETFE), polyvinyl fluoride (PVF), and polyvinylidene fluoride (PVDF).

Aspect 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.

Aspect 16: The anode electrode of aspect 15, wherein the first surface is flat or smooth and the second surface includes uneven features.

Aspect 17: The anode electrode of aspects 15-16, wherein one or both of the first surface and the second surface include an uneven shape.

Aspect 18: An anode electrode according to aspects 15 to 17, wherein the contours of the first surface or the second surface include one or more of corrugations, notches, rounded hills and/or valleys, and grooves.

Aspect 19: The anode electrode of aspects 15-18, wherein the second porous layer has a third surface opposite the second surface, and 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 forming a second transport channel.

Aspect 20: A battery comprising a pressure vessel and an electrode stack disposed within the pressure vessel, the electrode stack holding an electrolyte membrane, the electrode stack including alternating cathode and anode electrodes separated by a separator, the anode electrode including one or more porous layers, each of the porous layers including a porous substrate and a catalyst layer overlying the porous substrate, the catalyst layer including a transition metal, and at least one of the at least one porous layer including a surface having characteristics that facilitate hydrogen gas transport.

Aspect 21: A method for forming an electrode for a metal-hydrogen 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.

Aspect 22: The method of aspect 21, wherein coating the one or more porous substrates with a catalytic layer comprises electroplating the porous substrate with the catalytic layer, the catalytic layer comprising a transition metal alloy.

Aspect 23: The method of aspects 21-22, wherein electroplating the porous substrate with a catalytic layer is performed in a bath containing two or more of Ni, Co, Cr, Mo, Fe, Zn, S, and W.

Aspect 24: The method of aspects 21-23, further comprising leaching the porous layer to remove some of the metal from the catalyst layer.

Aspect 25: The method of aspects 21-24, wherein the transition metal alloy comprises Mo, and leaching comprises removing Mo from the porous layer.

Aspect 26: The method of aspects 21-25, wherein leaching comprises immersing the porous layer in an alkaline solution comprising KOH.

Aspect 27: The method of aspects 21-26, wherein the leaching is performed at a temperature greater than room temperature.

Aspect 28: The method of any one of aspects 21 to 27, wherein the temperature is from about 40°C to about 80°C.

Aspect 29: The method of aspects 21-28, further comprising an annealing step following the leaching step.

Aspect 30: The method of any one of aspects 21 to 29, wherein the annealing step includes annealing in a furnace under a diluted hydrogen atmosphere at 100°C to 500°C.

Aspect 31: The method of aspects 21-30, wherein forming the surface features includes forming one of corrugations, notches, rounded hills and/or valleys, and grooves.

Aspect 32: The method of aspects 21-31, further comprising modifying at least one porosity of the porous substrate.

Aspect 33: The method of aspects 21-32, further comprising coating at least one of the porous layers with a surface affinity modifying material to provide wet proofing.

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

Aspect 35: The method of aspects 21-34, further comprising further 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.

The foregoing description of the disclosure has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. The breadth and scope of the 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 in order to best explain the principles of the disclosure and its practical application, thereby enabling others skilled in the art to understand the disclosure for various embodiments, with various modifications suited to the particular use contemplated. It is intended that the scope of the disclosure be defined by the following claims and their equivalents.

Claims (35)

1. An electrode for a metal hydride battery, comprising:
one or more porous layers, each of the porous layers including a porous substrate and a catalytic layer overlying the porous substrate, the catalytic layer including a transition metal;
at least one of the at least one porous layers comprises a surface having characteristics that facilitate hydrogen gas transport;
electrode. The electrode of claim 1, wherein the at least one porous layer includes a plurality of porous layers, and a first surface of a first porous layer and a second surface of a second porous layer having a topographical feature have a contour that forms a hydrogen gas transport channel. The electrode of claim 1, wherein each of the porous substrates of the 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. The electrode of 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. The electrode of claim 3, wherein each of the porous substrates of the at least one porous layer comprises the metal foam or the metal alloy foam. The electrode according to claim 1, wherein the catalyst layer is a bifunctional catalyst that contributes to both the hydrogen evolution reaction (HER) and the hydrogen oxidation reaction (HOR). The electrode of claim 6, wherein the bifunctional 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. The electrode of claim 6, wherein the transition metal of the bifunctional catalyst includes two or more of Ni, Co, Cr, Mo, Fe, Zn, Sn, and W. The electrode of claim 6, 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. The electrode according to claim 8, wherein the transition metal alloy is a NiMoCo alloy or a NiMo alloy. The electrode of claim 1, wherein the at least one porous layer includes a first porous layer, a second porous layer, and a third porous layer disposed between the first and second porous layers, and the third porous layer has a first surface contour that is different from a second surface contour of the first or second porous layers. The electrode of claim 11, wherein the geometric features include one or more of the following: corrugations, notches, rounded hills and/or valleys, and grooves. The electrode of claim 1, 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. The electrode of claim 13, wherein the moisture resistant material comprises one of polyethylene, polypropylene, partially or fully fluorinated polymers, polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEB), polyethylene tetrafluoroethylene (ETFE), polyvinyl fluoride (PVF), and polyvinylidene fluoride (PVDF). a first porous layer having a first surface;
a second porous layer adjacent to the first porous layer and having a second surface;
Equipped with
the first surface of the first porous layer and the second surface of the second porous layer form hydrogen gas transport channels;
Anode electrode, The anode electrode of claim 15, wherein the first surface is flat or smooth and the second surface includes an uneven shape. The anode electrode according to claim 15, wherein one or both of the first surface and the second surface include a concave-convex shape. The anode electrode of claim 17, wherein the irregularities of the first surface or the second surface include one or more of the following: waves, notches, rounded hills and/or valleys, and grooves. the second porous layer has a third surface opposite the second surface;
the anode electrode further comprising 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 15. Pressure vessels;
an electrode stack disposed within said pressure vessel for holding an electrolyte;
Equipped with
the electrode stack includes alternating stacked cathode and anode electrodes separated by a separator;
The anode electrode includes one or more porous layers, each of the porous layers including a porous substrate and a catalyst layer overlying the porous substrate, the catalyst layer including a transition metal,
at least one of the at least one porous layers comprises a surface having characteristics that facilitate hydrogen gas transport;
battery. 1. A method of forming an electrode for a metal hydride battery, comprising the steps of:
Obtaining one or more porous substrates;
forming surface features on at least one surface of the porous substrate;
coating the one or more porous substrates with a catalyst layer to form a porous layer;
connecting the porous layers to form electrodes;
The method according to claim 1, 22. The method of claim 21, wherein coating the one or more porous substrates with the catalyst layer comprises electroplating the porous substrate with the catalyst layer, the catalyst layer comprising a transition metal alloy. 23. The method of claim 22, wherein the step of electroplating the porous substrate with the catalytic layer is performed in a bath containing two or more of Ni, Co, Cr, Mo, Fe, Zn, S, and W. 22. The method of claim 21, further comprising leaching the porous layer to remove some metal from the catalyst layer. 25. The method of claim 24, wherein the transition metal alloy includes Mo, and the leaching includes removing Mo from the porous layer. 25. The method of claim 24, wherein the leaching comprises immersing the porous layer in an alkaline solution comprising KOH. The method of claim 26, wherein the leaching is carried out at a temperature above room temperature. The composition of claim 27, wherein the temperature is from about 40°C to about 80°C. 25. The method of claim 24, further comprising an annealing step after the leaching. The apparatus of claim 29, wherein the annealing step includes annealing in a furnace under a dilute hydrogen atmosphere at a temperature between 100°C and 500°C. 22. The method of claim 21, wherein the step of forming surface features includes forming one of corrugations, notches, rounded hills and/or valleys, and grooves. 22. The method of claim 21, further comprising modifying the porosity of at least one of the at least one porous substrate. 22. The method of claim 21, further comprising coating at least one of the porous layers with a surface affinity modifying material to provide moisture resistance. 22. The method of claim 21, wherein the step of connecting the porous layers to form the electrode includes laminating a first porous layer and a second porous layer such that the surface features form a first transport channel for transporting hydrogen gas between the first porous layer and the second porous layer. The method of claim 34, further comprising laminating a third porous layer to the second porous layer to form a second transport channel between the second and third porous layers.

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