Name: zinc-sponge battery electrodes that suppress dendrites
Uploaded: 2020-09-29T14:00:00
Description: Watch this Scientific Journal Video about Zinc-Sponge Battery Electrodes that Suppress Dendrites at JoVE.com

This research was funded by the United States Office of Naval Research.

1. An emulsion-based method to create Zn-sponge electrodes
<ol>
	<li>Add 2.054 mL of deionized water to a 100 mL glass beaker.</li>
	<li>Add 4.565 mL of decane to the beaker.</li>
	<li>Stir in 0.1000 &#177; 0.0003 g of sodium dodecyl sulfate (SDS) until dissolved.</li>
	<li>Stir in 0.0050 &#177; 0.0003 g of water-soluble medium viscosity carboxymethyl cellulose (CMC) sodium salt by hand for 5 min or until the CMC is fully dissolved. 
	NOTE: Use plastic or plastic-coated stirring tools. Stirring with tools...

<ol>
	<li>Parker, J. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retaining+the+3D+Framework+of+Zinc+Sponge+Anodes+upon+Deep+Discharge+in+Zn-Air+Cells.">Retaining the 3D Framework of Zinc Sponge Anodes upon Deep Discharge in Zn-Air Cells.</a> ACS Applied Materials &amp; Interfaces. 6 (22), 19471-19476 (2014).</li><li>Parker, J. F., Chervin, C. N., Nelson, E. S., Rolison, D. R., Long, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Wiring+zinc+in+three+dimensions+re-writes+battery+performance-dendrite-free+cycling.">Wiring zinc in three dimensions re-writes battery performance-dendrite-free cycling.</a> Energy &amp; Environmental Science. 7, 1117-1124 (2014).</li><li>Parker, J. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rechargeable+nickel-3D+zinc+batteries:+An+energy-dense,+safer+alternative+to+lithium-ion.">Rechargeable nickel-3D zinc batteries: An energy-dense, safer alternative to lithium-ion.</a> Science. 356 (6336), 415-418 (2017).</li><li>Ko, J. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Robust+3D+Zn+sponges+enable+high-power,+energy-dense+alkaline+batteries.">Robust 3D Zn sponges enable high-power, energy-dense alkaline batteries.</a> ACS Applied Energy Materials. 2 (1), 212-216 (2018).</li><li>Hopkins, B. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabricating+architected+zinc+electrodes+with+unprecedented+volumetric+capacity+in+rechargeable+alkaline+cells.">Fabricating architected zinc electrodes with unprecedented volumetric capacity in rechargeable alkaline cells.</a> Energy Storage Materials. 27, 370-376 (2020).</li><li>Hopkins, B. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-cost+green+synthesis+of+zinc+sponge+for+rechargeable,+sustainable+batteries.">Low-cost green synthesis of zinc sponge for rechargeable, sustainable batteries.</a> Sustainable Energy &amp; Fuels. 4, 3363-3369 (2020).</li><li>Yufit, V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Operando+Visualization+and+Multi-scale+Tomography+Studies+of+Dendrite+Formation+and+Dissolution+in+Zinc+Batteries.">Operando Visualization and Multi-scale Tomography Studies of Dendrite Formation and Dissolution in Zinc Batteries.</a> Joule. 3 (2), 485-502 (2019).</li><li>Ashby, M. 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R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+areal-energy+standard+to+validate+air-breathing+electrodes+for+rechargeable+zinc-air+batteries.">An areal-energy standard to validate air-breathing electrodes for rechargeable zinc-air batteries.</a> Advanced Energy Materials. 10 (30), 2001287 (2020).</li><li>Jayasayee, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cold+Sintering+as+a+Cost-Effective+Process+to+Manufacture+Porous+Zinc+Electrodes+for+Rechargeable+Zinc-Air+Batteries.">Cold Sintering as a Cost-Effective Process to Manufacture Porous Zinc Electrodes for Rechargeable Zinc-Air Batteries.</a> Processes. 8 (5), 592 (2020).</li><li>Chamoun, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> NPG Asia Materials. 7, 178 (2015).</li><li>Kang, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D+Porous+Copper+Skeleton+Supported+Zinc+Anode+toward+High+Capacity+and+Long+Cycle+Life+Zinc+Ion+Batteries.">3D Porous Copper Skeleton Supported Zinc Anode toward High Capacity and Long Cycle Life Zinc Ion Batteries.</a> ACS Sustainable Chemistry &amp; Engineering. 7 (3), 3364-3371 (2019).</li><li>Yu, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ag-Modified+Cu+Foams+as+Three-Dimensional+Andoes+for+Rechargeable+Zinc-Air+Batteries.">Ag-Modified Cu Foams as Three-Dimensional Andoes for Rechargeable Zinc-Air Batteries.</a> ACS Applied Nano Materials. 2 (5), 2679-2688 (2019).</li><li>Stumpp, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlled+Electrodeposition+of+Zinc+Oxide+on+Conductive+Meshes+and+Foams+Enabling+Its+Use+as+Secondary+Anode.">Controlled Electrodeposition of Zinc Oxide on Conductive Meshes and Foams Enabling Its Use as Secondary Anode.</a> Journal of The Electrochemical Society. 165 (10), 461-466 (2018).</li><li>Stock, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+Strategy+for+Zinc+Anodes+with+Enhanced+Utilization+and+Retention:+Electrodeposited+Zinc+Oxide+on+Carbon+Mesh+Protected+by+Ionomeric+Layers.">Design Strategy for Zinc Anodes with Enhanced Utilization and Retention: Electrodeposited Zinc Oxide on Carbon Mesh Protected by Ionomeric Layers.</a> ACS Applied Energy Materials. 1 (10), 5579-5588 (2018).</li><li>Li, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatially+homogeneous+copper+foam+as+surface+dendrite-free+host+for+zinc+metal+anode.">Spatially homogeneous copper foam as surface dendrite-free host for zinc metal anode.</a> Chemical Engineering Journal. 379, 122248 (2020).</li><li>Zhou, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Graphene+oxide-modified+zinc+anode+for+rechargeable+aqueous+batteries.">Graphene oxide-modified zinc anode for rechargeable aqueous batteries.</a> Chemical Engineering Science. 194, 142-147 (2019).</li><li>McDevitt, K. M., Mumm, D. R., Mohraz, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improving+Cyclability+of+ZnO+Electrodes+through+Microstructural+Design.">Improving Cyclability of ZnO Electrodes through Microstructural Design.</a> ACS Applied Energy Materials. 2 (11), 8107-8117 (2019).</li><li>Wang, C., Zhu, G., Liu, P., Chen, Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monolithic+Nanoporous+Zn+Anode+for+Rechargeable+Alkaline+Batteries.">Monolithic Nanoporous Zn Anode for Rechargeable Alkaline Batteries.</a> ACS Nano. 14 (2), 2404-2411 (2020).</li><li>Drillet, J. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+Novel+Zinc/Air+Fuel+Cell+with+a+Zn+Foam+Anode,+a+PVA/KOH+Membrane+and+a+MnO2/SiOC-based+Air+Cathode.">Development of a Novel Zinc/Air Fuel Cell with a Zn Foam Anode, a PVA/KOH Membrane and a MnO2/SiOC-based Air Cathode.</a> ECS Transactions. 28, 13-24 (2010).</li><li>Bozzini, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphological+evolution+of+Zn-sponge+electrodes+monitored+by+in+situ+X-ray+computed+microtomography.">Morphological evolution of Zn-sponge electrodes monitored by in situ X-ray computed microtomography.</a> ACS Applied Energy Materials. , (2020).</li><li>Yang, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Do+Zinc+Dendrites+Exist+in+Neutral+Zinc+Batteries:+A+Developed+Electrohealing+Strategy+to+In+Situ+Rescue+In-Service+Batteries.">Do Zinc Dendrites Exist in Neutral Zinc Batteries: A Developed Electrohealing Strategy to In Situ Rescue In-Service Batteries.</a> Advanced Materials. 31, 1903778 (2019).</li><li>Yang, Q., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen-Substituted+Graphdiyne+Ion+Tunnels+Directing+Concentration+Redistribution+for+Commercial-Grate+Dendrite-Free+Zinc+Anodes.">Hydrogen-Substituted Graphdiyne Ion Tunnels Directing Concentration Redistribution for Commercial-Grate Dendrite-Free Zinc Anodes.</a> Advanced Materials. 32, 2001755 (2020).</li><li>Narayanan, S. R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Materials+challenges+and+technical+approaches+for+realizing+inexpensive+and+robust+iron-air+batteries+for+large-scale+energy+storage.">Materials challenges and technical approaches for realizing inexpensive and robust iron-air batteries for large-scale energy storage.</a> Solid State Ionics. 216, 105-109 (2012).</li><li>Xiong, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+Heat+Treatment+on+the+Discharge+Behavior+of+Mg-6wt.%Al-1wt.%Sn+Alloy+as+Anode+for+Magnesium-Air+Batteries.">Effects of Heat Treatment on the Discharge Behavior of Mg-6wt.%Al-1wt.%Sn Alloy as Anode for Magnesium-Air Batteries.</a> Journal of Materials Engineering and Performance. 26, 2901-2911 (2017).</li><li>Hopkins, B. J., Shao-Horn, Y., Hart, D. 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Modifications and troubleshooting associated with these protocols include filling the freshly mixed Zn paste into a mold cavity. Care should be taken to avoid air pockets. Unwanted voids can be decreased by tapping the mold after filling or while filling. Because the aqueous Zn paste is dry, pressure can be applied directly to the Zn paste to push out air pockets while filling up the mold cavity.
A limitation of the methods is that Zn-sponge pore structure is disordered, but the Zn and porogen...

The purpose of the reported fabrication methods is to create zinc (Zn) sponge electrodes that suppress dendrite formation and shape change. Historically, these problems have limited the cycle life of Zn batteries. Zinc-sponge electrodes have resolved these issues, enabling Zn batteries with longer cycle lives1,2,3,4,5,6. The sponge structure suppresses dendrite formation and shape change because (1) the fused Zn framework electrically wires the entire volume of the sponge; (2) the pores hold zincate near the Zn-sponge surface; and (3) the sponge has a high surface area that decreases local current density below values identified to sprout dendrites in alkaline electrolytes7. However, if sponge surface area is too high, substantial corrosion occurs5. If the sponge pores are too large, the sponge will have a low volumetric capacity5. Also, if the sponge pores are too small, the Zn electrode will have insufficient electrolyte to access Zn during discharge, resulting in low power and capacity5,6.
The rationale behind the reported fabrication methods is to create Zn sponges with appropriate sponge porosities and pore diameters. Experimentally, we find that Zn sponges with porosities from 50 to 70% and pore diameters near 10&#160;&#181;m cycle well in full-cell batteries and display low corrosion rates5. We note that existing methods to manufacture commercial metal foams fail to achieve similar morphologies on these length scales8, so the reported fabrication methods are needed.
The advantages of the methods reported here over alternatives are characterized by fine control of sponge features and by the ability to fabricate large, dense Zn sponges with technologically relevant areal-capacity values5,6,9,10. Alternative methods to create Zn foams may be unable to create comparable 10 &#181;m pores with sponge porosities near 50%. Such alternatives may, however, require less energy to fabricate because they avoid high-temperature processing steps. Alternative processes include the following strategies: cold sintering Zn particles11, depositing Zn on three-dimensional host structures12,13,14,15,16,17, cutting Zn foil into two-dimensional foams18, and creating Zn foams via spinodal decomposition19 or percolation dissolution20.
The context of the reported methods in the wider body of the published literature is primarily established by work from Drillet et al.21. They adapted methods of fabricating porous ceramics to create one of the earliest reported three-dimensional, albeit fragile, Zn foams for batteries. These authors, however, failed to demonstrate rechargeability, likely because of the poor connectivity between the Zn particles. Prior to rechargeable Zn-sponge electrodes, the best alternative to a Zn foil electrode was a Zn-powder electrode, wherein Zn powder is mixed with a gel electrolyte. Zinc-powder electrodes are commercially used in primary alkaline batteries (Zn&#8211;MnO2) but have poor rechargeability because Zn particles become passivated by Zn oxide (ZnO), which can increase local current density that spurs dendrite growth3,22. We note that there are other dendrite-suppression strategies that do not involve foam or sponge architectures23,24.
The reported Zn-sponge fabrication methods require a tube furnace, sources of air and nitrogen gas (N2), and a fume hood. All steps can be performed at a lab desk without environmental control, but exhaust from the tube furnace during heat treatment should be piped to a fume hood. Resulting electrodes are appropriate for those interested in creating rechargeable Zn electrodes capable of high areal capacity (&#62; 10 mAh cmgeo&#8211;2)6.
The first reported fabrication method is an emulsion-based route to create Zn-sponge electrodes. The second, is an aqueous-based route. An advantage of the emulsion route is its ability to create Zn paste that, when dried, is easy to demold from a mold cavity. A disadvantage is its reliance on expensive materials. For the aqueous route, sponge preforms can be challenging to demold, but this process uses inexpensive and abundant materials.
Both methods involve mixing Zn particles with a porogen and viscosity-enhancing agent. The resulting mixture is heated under N2 and then breathing air (not synthetic air). During heating under N2, the Zn particles anneal and the porogen decomposes; under breathing air, the annealed Zn particles fuse and the porogen burns out. These processes yield metal foams or sponges. The mechanical and electrochemical properties of the Zn sponges can be tuned by varying Zn-to-porogen mass ratio, heating time under N2 and air, and size and shape of the Zn and porogen particles.

<table>
	<tbody>
		<tr>
			<td>Corn starch</td>
			<td>Argo</td>
			<td>Not applicable</td>
			<td>This acts as a porogen and viscosity-enhancing agent.</td>
		</tr>
		<tr>
			<td>Decane</td>
			<td>MilliporeSigma</td>
			<td>D901</td>
			<td></td>
		</tr>
		<tr>
			<td>Medium viscosity water-soluble carboxymethyl cellulose (CMC) sodium salt</td>
			<td>MilliporeSigma</td>
			<td>C4888-500G</td>
			<td>This CMC acts primarily as a viscosity-enhancing agent.</td>
		</tr>
		<tr>
			<td>Overhead stirrer</td>
			<td>Caframo Lab Solutions</td>
			<td>BDC3030</td>
			<td></td>
		</tr>
		<tr>
			<td>Small cylindrical models for Zn sponges</td>
			<td>VWR</td>
			<td>66014-358</td>
			<td>The caps of the vials can be used as molds.</td>
		</tr>
		<tr>
			<td>Sodium dodecyl sulfate</td>
			<td>MilliporeSigma</td>
			<td>436143</td>
			<td></td>
		</tr>
		<tr>
			<td>Water-insoluble IonSep CMC 52 preswollen carboxymethyl cellulose resin</td>
			<td>BIOpHORETICS</td>
			<td>B45019.01</td>
			<td>This CMC acts as a porogen and viscosity-enhancing agent.</td>
		</tr>
		<tr>
			<td>Zn powder</td>
			<td>EverZinc</td>
			<td>Custom order</td>
			<td></td>
		</tr>
	</tbody>
</table>

zinc-sponge battery electrodes that suppress dendrites

We report two methods to create zinc-sponge electrodes that suppress dendrite formation and shape change for rechargeable zinc batteries. Both methods are characterized by creating a paste made of zinc particles, organic porogen, and viscosity-enhancing agent that is heated under an inert gas and then air. During heating under the inert gas, the zinc particles anneal together, and the porogen decomposes; under air, the zinc fuses and residual organic burns out, yielding an open-cell metal foam or sponge. We tune the mechanical and electrochemical properties of the zinc sponges by varying zinc-to-porogen mass ratio, heating time under inert gas and air, and size and shape of the zinc and porogen particles. An advantage of the reported methods is their ability to finely tune zinc-sponge architecture. The selected size and shape of the zinc and porogen particles influence the morphology of the pore structure. A limitation is that resulting sponges have disordered pore structures that result in low mechanical strength at low volume fractions of zinc (&#60;30%). Applications for these zinc-sponge electrodes include batteries for grid-storage, personal electronics, electric vehicles, and electric aviation. Users can expect zinc-sponge electrodes to cycle up to 40% depth of discharge at technologically relevant rates and areal capacities without the formation of separator-piercing dendrites.

Resulting, fully heat-treated, emulsion-based Zn sponges have densities of 2.8 g&#8729;cm&#8211;3 while aqueous-based sponges approach 3.3 g&#8729;cm&#8211;3. During heating under air, a layer of ZnO forms on the Zn surfaces, which should have a thickness of 0.5&#8211;1.0 &#181;m (observed using scanning electron microscopy)5. The solid in the resulting sponges should be 72% Zn (emulsion version) or 78% Zn (aqueous version) with the remainder being ZnO (measured by X-ray diff...

Watch this Scientific Journal Video about Zinc-Sponge Battery Electrodes that Suppress Dendrites at JoVE.com

Zinc-Sponge Battery Electrodes that Suppress Dendrites

The goal of the reported protocols is to create rechargeable zinc-sponge electrodes that suppress dendrites and shape change in zinc batteries, such as nickel&#8211;zinc or zinc&#8211;air.

We report two methods to create zinc-sponge electrodes that suppress dendrite formation and shape change for rechargeable zinc batteries. Both methods are ...

This protocol provides an easy, low-cost method of creating a zinc electrode that suppresses dendrites when cycled in an alkaline battery. The main advantage of this technique is that one can easily tune the structure of the zinc electrode by changing zinc particle size, type of origin and its size, or heat treatment protocol. The metal sponge created using this protocol falls into the relative density and cell size that can be difficult to achieve using standard metal foam manufacturing methods.Begin by adding 2.054 milliliters of deionized water and 4.565 milliliters of decane to a 100 milliliter glass beaker. Then dissolve 0.1 gram of SDS by stirring the solution. Next, add five milligrams of water soluble medium viscosity CMC sodium salt to the beaker and stir for five minutes or until dissolved.Use plastic or plastic-coated stirring tools because a metallic surface can adversely affect resulting zinc sponges. Add and stir 0.844 grams of water insoluble pre-swollen carboxymethyl cellulose resin to the beaker. Keep the beaker on an overhead paddle stirrer equipped with a plastic paddle and stir the entire mixture at 1, 000 RPM for five minutes.Add 50 grams of zinc powder and continue stirring for five more minutes. After five minutes, stop the stirrer and remove the beaker. Place the beaker in a desiccator for five minutes at room temperature to outcast the mixture and its contents under vacuum.Portion the zinc paste into polypropylene molds of approximately 10 millimeter diameter and five millimeter height to air-dry the paste overnight. After drying, carefully remove the zinc paste from the molds and place them into a mesh casing that rests on a notched alumina holder. Place the assembly into a tube furnace with ports to flow gas in and out of the tube.Pipe nitrogen gas into the furnace for 30 minutes at a rate of 5.7 centimeters per minute to purge the furnace of air. After 30 minutes of purging, throttle the nitrogen gas to a constant rate of 2.8 centimeters per minute. Program the temperature of the furnace to increase linearly from 20 to 369 degrees Celsius over the course of 68 minutes, hold at 369 degrees Celsius for five hours, rise linearly from 369 to 584 degrees Celsius over the course of 105 minutes, and then turn off.Start the furnace program as the nitrogen continues to flow. Stop the nitrogen gas flow manually after the five hours of temperature hold and pipe in breathing air at 2.8 centimeters per minute. Let the furnace cool to room temperature once the heating program stops while keeping the breathing air flowing.Finally, remove the cooled zinc sponges and either saw or sand them to the desired dimensions. Add 10.5 milliliters of deionized water to a 100 milliliter glass beaker. Then add 0.12 grams of water soluble high-viscosity cellulose gum and stir using a plastic-coated stirring tool.Vortex and stir this mixture by hand for five minutes or until the cellulose gum is dissolved. Add 2.4 grams of cornstarch while vortexing the beaker for two minutes and then add 120 grams of prepared zinc powder while vortexing for an additional two minutes. Once done, press the resulting zinc paste into the desired mold cavities and leave them to dry overnight at 70 degrees Celsius in open air in a furnace.After drying, carefully remove the zinc paste from the molds and place them into a mesh casing that rests on a notched alumina holder. Place the assembly into a tube furnace with ports to flow gas in and out of the tube. Pipe nitrogen gas into the furnace for 30 minutes at a rate of 5.7 centimeters per minute to purge the furnace of air.After 30 minutes of purging, throttle the nitrogen gas to a constant rate of 2.8 centimeters per minute. Program the temperature of the furnace to increase linearly from 20 to 369 degrees Celsius over the course of 68 minutes, hold at 369 degrees Celsius for five hours, rise linearly from 369 to 584 degrees Celsius over the course of 105 minutes, and then turn off. Start the furnace program as the nitrogen continues to flow.After five hours of temperature hold, stop the nitrogen gas flow manually and pipe in breathing air at 2.8 centimeters per minute. Allow the furnace to cool to room temperature once the heating program stops while keeping the breathing air flowing. Finally, remove the cooled zinc sponges and saw or sand them to the desired dimensions.This protocol was used to produce emulsion-based zinc sponges with densities of 2.8 grams per cubic centimeter and aqueous-based sponges with densities of 3.3 grams per cubic centimeter. The zinc sponges should be rigid and brittle. Their cross-sections should look similar to the ones shown here.All properties of the resulting zinc sponges should fall within the ranges provided in the text manuscript. The zinc sponge electrode shows a cycling stability at a gravimetric capacity of 328 milliampere hours per gram of zinc, which maps to a 43%depth of discharge. After extensive electrochemical cycling of the constructed zinc electrodes to estimate their efficiency, no dendrites were observed in scanning electron micrographs of the zinc sponge electrodes.The surface of the zinc sponge undergoes restructuring during cycling. The deeper the level of discharge and the greater the cycle life, the greater the amount of restructuring. When attempting this protocol, remember to stir the mixture with a plastic-coated tool.Similar fabrication processes could be used to create other types of metal foams based on different metals for numerous applications.

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