Research at Argonne National Laboratory was funded by U.S. Department of Energy, FreedomCAR and Vehicle Technologies Office. Use of the Advanced Photon Source and research carried out in the Electron Microscopy Center at Argonne National Laboratory was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.

Please consult all relevant Material Safety Data Sheets (MSDS) before use. Several of the chemicals used in these syntheses are acutely toxic and carcinogenic. Nanomaterials may have additional hazards compared to their bulk counterpart. Please use all appropriate safety practices when performing a nanocrystal reaction including the use of engineering controls (fume hood, glovebox) and personal protective equipment (safety glasses, gloves, lab coat, full length pants, closed-toe shoes). Portions of the following procedures involve standard air-free handling techniques.
1. Synthesis of Cathode Materials
Note: Cathode materials can be synthesized by either atomic layer deposition or wet chemistry reaction.
<ol>
	<li>Atomic Layer Deposition (ALD)
	<ol>
		<li>Disperse 5 g of porous carbon in 100 ml 1 M KMnO4 solution under magnetic stirring for 12 hr.</li>
		<li>Spread 100 mg of the oxidized carbon powder onto a stainless steel tray of the ALD instrument, and clamp a stainless steel mesh cover over the tray.</li>
		<li>Hold the carbon powder in the tray at 200 &#176;C under continuous flow of 300 sccm ultra-high-purity nitrogen carrier gas at 1 Torr pressure for 30 min.</li>
		<li>Treat the carbon powder with a complete ALD cycle as follows. 
		Note: Take Pd nanoparticles as an example of the electrocatalysts in this protocol. Reagents can be changed according to specific requirements. All reagents are used as-received without any further purification.
		<ol>
			<li>Expose the carbon substrate (100 mg) to palladium hexafluoroacetylacetonate (Pd(hfac)2, 99.9%) at 200 &#176;C for 100 min.</li>
			<li>Purge the tray with continuous flow of 300 sccm ultra-high-purity nitrogen carrier gas at 1 Torr pressure for 300 min.</li>
			<li>Expose the carbon substrate to formalin (HCHO 37 wt. % in H2O) at 200 &#176;C for 100 min.</li>
			<li>Purge the tray with continuous flow of 300 sccm ultra-high-purity nitrogen carrier gas at 1 Torr pressure for 300 min.</li>
		</ol>
		</li>
		<li>Repeat ALD cycle as necessary. Usually 3-10 repetitions.</li>
	</ol>
	</li>
	<li>Wet-chemistry Reaction 
	Note: Take Fe nanoparticles as an example of the electrocatalyst in this protocol. Reagents can be changed according to specific requirements. All reagents are used as-received without any further purification.
	<ol>
		<li>Disperse 5 g of porous carbon in 100 ml 1 M KMnO4 solution under magnetic stirring for 12 hr.</li>
		<li>Wash the oxidized carbon with deionized water.</li>
		<li>Filter the washed carbon with a filter flask fitted with a glass fiber, and then dry it in an oven at 110 &#176;C for 12 hr.</li>
		<li>Disperse the dried carbon in 100 ml deionized water, then add 1 g of FeCl3 under magnetic stirring.</li>
		<li>Adjust the pH value to about 9, using 1 M NaOH solution.</li>
		<li>Stir the resulting slurry for 5 hr, and then filter the slurry with a filter flask fitted with a glass fiber.</li>
		<li>Wash the product with deionized water and ethanol. Then dry it in an oven at 110 &#176;C for overnight.</li>
		<li>Heat-treat the product at 450 &#176;C with continuous flow of H2/Ar mixture (4% H2) in a quartz tube furnace. Use a flow rate of 100 ml/min for 5 hr.</li>
	</ol>
	</li>
</ol>
2. Preparation of Electrodes and Electrolyte
<ol>
	<li>Cathode
	<ol>
		<li>Mix the as-prepared cathode material and binder poly(vinylidene fluoride) (PVDF) in a 4:1 weight ratio. 
		Note: The total of the mixture depends on the amount of the cathodes. The loading of cathode material on each piece is in the range of 0.1-1 mg.</li>
		<li>Add 1-methyl-2-pyrrolidinone (NMP) to the mixture, and stir well to make an even-textured slurry. Add NMP at about three times the weight of the mixture.</li>
		<li>Coat the slurry onto carbon paper by a doctor blade with a thickness around 100 &#181;m.</li>
		<li>Dry the laminate in a vacuum oven at 100 &#176;C for overnight.</li>
		<li>Punch the laminate into disks with a hole puncher to a diameter of 7/16 inches, and weigh it.</li>
	</ol>
	</li>
	<li>Aprotic Electrolyte
	<ol>
		<li>Dry lithium trifluoromethanesulfonate (LiCF3SO3) in a vacuum oven at 100 &#176;C for overnight.</li>
		<li>Add dried LiCF3SO3 in tetraethylene glycol dimethyl ether (TEGDME; H2O ~ 10 ppm) with a concentration of 1 mol/L, then stir the solution with magnetic stirring until the salt is dissolved.</li>
		<li>Keep the electrolyte in a glovebox filled with Ar.</li>
	</ol>
	</li>
	<li>Anode
	<ol>
		<li>Punch the lithium foil/chips into disks with a hole puncher to a diameter of 7/16 inches.</li>
	</ol>
	</li>
</ol>
3. Electrochemical Testing
<ol>
	<li>Assembly of Swagelok Cell 
	Note: All the steps of the assembly are operated in a glovebox filled with Ar, except 3.1.9.
	<ol>
		<li>Assemble the Swagelok set as shown in Figure 1a. Tighten the anode end, and loosen the cathode end.</li>
		<li>Put a piece of lithium metal chip (diameter 7/16 inches) on the top of the stainless steel rod of the anode end.</li>
		<li>Put a piece of glass fiber separator (diameter 1/2 inches) on the top of the lithium metal anode.</li>
		<li>Add 5-7 drops of electrolyte to fully wet the glass fiber separator. Gently press the separator to remove bubbles.</li>
		<li>Put a piece of cathode on the top of the wetted separator, with the active material facing the anode.</li>
		<li>Cover the cathode with a piece of aluminum mesh (diameter 7/16 inches).</li>
		<li>Press the above mentioned layers with the aluminum tube, then tighten the cathode end.</li>
		<li>Seal the whole Swagelok cell in a glass chamber, and fix the chamber with a clamp, as shown in Figure 1.</li>
		<li>Take the whole cell out of glovebox. Connect the glass chamber to an ultra-high-purity oxygen tank, and purge it with continuous oxygen flow at 1 atm pressure for 30 min.</li>
	</ol>
	</li>
	<li>Battery Performance Testing
	<ol>
		<li>Set a thermostat to 25 &#176;C.</li>
		<li>Put cells and electrodes (electronic clips connected to the equipment by a cable) into the thermostat, and fix them.</li>
		<li>Clip the cathode and anode on glass chamber with corresponding electronic clips.</li>
		<li>Open the operating software of the battery test system, and select the channel connected with the cable.</li>
		<li>Set a procedure of the electrochemical testing. 
		Note: Set the current density of 100 mA/gactive material, and voltage range of 2.2-4.5 V.
		<ol>
			<li>Set the discharge cut-off voltage of 2.2 V for discharge test.</li>
			<li>Set the discharge/charge step-time of 5 or 10 hr for capacity-controlled cycling test.</li>
			<li>Set the discharge cut-off voltage of 2.2 V and charge cut-off voltage of 4.5 V for voltage-controlled cycling test.</li>
		</ol>
		</li>
		<li>Run the procedure by clicking the &#34;run&#34; button on the software interface.</li>
	</ol>
	</li>
	<li>Disassembly and cleaning of the cell
	<ol>
		<li>Disassemble cells in a glovebox.</li>
		<li>Keep the electrodes in glass vials for the following characterizations. Transfer other cell parts out of the glovebox.</li>
		<li>Put the Swagelok parts, stainless steel rods, aluminum tubes, and aluminum meshes in acetone solution (~ 20%) or deionized water in a beaker, and clean them with ultrasonication for 15-30 min.</li>
		<li>Dry the parts and glass chambers in a thermostat set to 60-80 &#176;C.</li>
	</ol>
	</li>
</ol>
4. Preparation of Characterization Specimens
Note: Specimens are prepared in a hood (for as-prepared materials) or a glovebox filled with Ar (for air-sensitive specimens).
<ol>
	<li>Specimens for SEM and XPS
	<ol>
		<li>Stick a carbon tape on the sample stage. The carbon tape can be as large as the sample stage, or as small as the specimen piece.</li>
		<li>Cut a piece of specimen about 5 mm2, and stick it on the carbon tape. 
		Note: The specimen can be any non-magnetic samples. For the specimens after electrochemical tests, wash them with the electrolyte solvent before stick to the carbon tape.</li>
		<li>Seal the air-sensitive specimens in a Mason jar before measurement.</li>
		<li>Operate the SEM34-36 or XPS37,38 according to the manufacturer&#39;s instructions.</li>
	</ol>
	</li>
	<li>Specimens for TEM
	<ol>
		<li>Mill 1 mg of the sample powder. 
		Note: For electrode specimens, scrape the active materials off carbon paper before milling.</li>
		<li>Load the sample powder onto a copper grid, and remove the loose powder.</li>
		<li>Load the copper grid to the sample holder of TEM. 
		Note: Get this step done as fast as possible for air-sensitive samples.</li>
		<li>Perform TEM.39-41</li>
	</ol>
	</li>
	<li>Specimens for High-energy XRD
	<ol>
		<li>Powder specimens
		<ol>
			<li>Seal one end of a polyimide tubing by clay or glue.</li>
			<li>Load the powder into the tubing.</li>
			<li>Seal the other end of the tubing.</li>
		</ol>
		</li>
		<li>Disk specimens 
		Note: To measure the active materials on electrode, another option is to scrape them off carbon paper and follow step 4.3.1.
		<ol>
			<li>Seal the sample pieces with a piece of polyamide tape. Seal by putting the samples in the middle of one piece of tape, and covering them with another piece of tape. 
			Note: For the specimens after electrochemical tests, wash them with the electrolyte solvent before sealing.</li>
		</ol>
		</li>
		<li>Operate the high-energy XRD42-44 in Advanced Photon Sources in Argonne National Laboratory.</li>
	</ol>
	</li>
	<li>Specimens for XANES
	<ol>
		<li>Powder samples
		<ol>
			<li>Dilute the samples if the concentration of the measured elements is high, using either boron nitride (BN) or carbon black as the dilute agent. Here, dilute to 3-5 wt. %.</li>
			<li>Press the powder into disk with the diameter of 7 mm and the thickness of around 1 mm, using a KBr Press Kit and 7 mm Die Set.</li>
			<li>Seal the disk with window film.</li>
		</ol>
		</li>
		<li>Disk specimens
		<ol>
			<li>Seal the specimen with window film.</li>
		</ol>
		</li>
		<li>Operate the high-energy XANES45-47 in Advanced Photon Sources in Argonne National Laboratory.</li>
	</ol>
	</li>
	<li>Specimens for ATR-FTIR
	<ol>
		<li>Clean the diamond attenuated total reflection (ATR) unit before and after measurement.</li>
		<li>Put specimens on the diamond unit for all samples interested.</li>
		<li>Perform ATR-FTIR spectrometry.48,49</li>
	</ol>
	</li>
	<li>Specimens for Raman Spectra
	<ol>
		<li>Put the specimen on a flat board (glass, stainless steel, etc.).</li>
		<li>Cover the specimen with a cover slide.</li>
		<li>Seal the set for air-sensitive samples.</li>
		<li>Perform Raman spectrometry.50,51</li>
	</ol>
	</li>
</ol>

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Commun. 4, 2438 (2013).</li><li>Zhong, L., 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=In+Situ+Transmission+Electron+Microscopy+Observations+of+Electrochemical+Oxidation+of+Li2O2.">In Situ Transmission Electron Microscopy Observations of Electrochemical Oxidation of Li2O2.</a> Nano Lett. 13, 2209-2214 (2013).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Hitachi S-4700 SEM Training &amp; Reference Guide. , (2015).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> SEM Hitachi S4700 User Manual. , (2015).</li><li>Goldstein, 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=.">.</a> Scanning Electron Microscopy and X-ray Microanalysis. , (2003).</li><li>. 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R., Sardela, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Practical Materials Characterization. , 1-41 (2014).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Beamline 9-BM-B,C: X-ray Absorption Spectroscopy Beamline. , (2015).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Beamline 20-BM-B: X-ray Absorption Spectroscopy Beamline. , (2015).</li><li>Bunker, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Introduction to XAFS: A Practical Guide to X-ray Absorption Fine Structure Spectroscopy. , (2010).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Nicolet FT-IR User's Guide. , (2015).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Nicolet iS5 User Guide. , (2015).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Renishaw inVia Raman Microscope Training Notebook. , (2015).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Renishaw InVia Quick Operation Summary. , (2015).</li><li>Mitchell, R. 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The authors have nothing to disclose.

Considering the sensitivity of Li-O2 battery system to air, especially CO2 and moisture, lots of steps in the protocol are necessary in order to reduce the interferents and to avoid side reactions. For example, the Swagelok-type cell is assembled in a glovebox filled with Ar with O2 &#60; 0.5 ppm and H2O &#60; 0.5 ppm; and all the cathode materials, electrolyte solvent and salt, glass fiber, Swagelok parts, and the glass chambers are dried before assembly to reduce the moisture contamination. The anode end is a stainless steel rod in order to avoid the direct contact between lithium metal and O2 and to protect the lithium anode. The whole Swagelok setup is placed into a pure-oxygen-filled glass chamber which guarantees a leak-proof container by sealing with O-ring and vacuum greases. Moreover, Al-mesh, the current-collector, can help to protect the brittle carbon cathode.
The electrochemical test demonstrate that the as-prepared cathode materials showed a superior electrochemical behavior in Li-O2 battery. Due to that, the catalyst nanoparticles were uniformly dispersed over the high surface area carbon support, and that the porous structure and surface area were well persevered by the catalysts deposition methods used in this protocol. The overall reaction of nonaqueous Li-O2 battery is 2Li+ + O2 + 2e- &#8594; Li2O2.2,3,7 Side reactions, such as electrolyte decomposition, are also likely to occur due to the activity of the materials and intermediates used in a cell. However, in the research at the present stage, the side reactions and byproducts (LiOH, Li2CO3, etc.) have been significantly reduced with the improvement of materials and synthesis technologies. As shown in Figure 2d, although there might be a small amount of byproducts, the amount is too low to be detected by XRD. Some surface-sensitive techniques, such as XPS, FT-IR, and Raman spectroscopy, are, therefore, used to detect the minor products, especially on the surface region. There is no doubt that the stability of the electrolytes is very critical in oxygen environment and electrochemical reactions. Ether-based electrolytes (e.g., TEGDME) are relatively stable at the present stage of Li-O2 battery research. However, their behavior still needs to be investigated during long-term cycling; and searching for stable electrolytes is the research priority presently.
There are some other characterization methods to establish the discharge yield, or byproducts, such as mass spectrometry (MS) and titration. However, in the current research stage, the battery system is much more stable and reversible, and the byproducts have been significantly reduced by the development of electrolyte and cathode materials which have been more stable to oxygen and the discharge products.3,13,15 In this case, MS and titration are not sensitive enough to estimate the discharge yield. Besides, LiO2, the intermediate product, cannot be detected by titration either, due to its extreme activity.
In this article, we have demonstrated a systematic and efficient protocol of routine tests of aprotic Li-O2 battery, including the performance test and characterization of battery materials and reaction products. The approaches of catalyst loading result in a uniform distribution of catalyst nanoparticles with preservation of the surface structure of carbon substrate. Appropriate assembly protocol optimizes the active materials and ensures the pure-O2 environment for the electrochemical reactions.

In 1996, Abraham and Jiang1 reported the first reversible non-aqueous Li-O2 battery consisting of a porous carbon cathode, an organic electrolyte, and a Li-metal anode. Since then, due to its extremely high theoretical energy density exceeding that of any other existing energy storage systems, the Li-O2 battery, which induces a current flow by the oxidation of lithium at the anode and the reduction of oxygen at the cathode (overall reaction Li+ + O2 + e- &#8596; Li2O2), has received significant interest recently.1-8
A cathode material with the following requirements would be able to cater for the needs of high performance of Li-O2 battery: (1) fast oxygen diffusion; (2) good electric and ionic conductivity; (3) high specific surface area; and (4) stability. Both the surface area and porosity of the cathode are critical for the electrochemical performance of Li-O2 batteries.9-12 The porous structure allows the deposition of solid discharge products generated from the reaction of Li cations with O2; and larger surface areas provide more active sites to accommodate electrocatalytic particles that accelerate the electrochemical reactions. Such electrocatalysts are added to the cathode material by certain deposition methods, which provide strong adhesion to the substrate and good control of the catalyst particles, with preservation of the original porous surface structure of the substrate.13-17 The as-prepared materials are tested in Swagelok-type cells as the cathode of aprotic Li-O2 battery. However, the performance of the cell not only depends on the nature of cathode materials, but also on the type of the aprotic electrolyte18-22 and Li-metal anode.23-26 More influences include the amount and concentration of the materials and the procedure used in the charge/discharge tests. Proper conditions and protocols would optimize and improve the overall performance of battery materials.
In addition to the results of the electrochemical test, the battery performance can be also evaluated by characterizing the pristine materials and the reaction products.27-33 Scanning electron microscopy (SEM) is used to investigate the surface microstructure of the cathode material and the morphology evolution of the discharge products. Transmission electron microscopy (TEM), X-ray absorption near edge structure (XANES), and X-ray photoelectron spectroscopy (XPS) can be used to determine the ultrastructure, chemical state, and component of elements, especially for that of catalyst nanoparticles. High-energy X-ray diffraction (XRD) is used for directly identifying the crystalline discharge products. Possible electrolyte decomposition can be determined by attenuated total reflection Fourier transform infrared (ATR-FTIR) and Raman spectra.
This article is a protocol that demonstrates a systematic and efficient arrangement of routine tests of the aprotic Li-O2 battery, including the preparation of battery materials and accessories, the electrochemical performance test, and characterization of pristine materials and reaction products. The detailed video protocol is intended to help new practitioners in the field avoid many common pitfalls associated with the performance testing and characterization of Li-O2 batteries.

<table border="0" cellpadding="0" cellspacing="0" width="830">
	<tbody>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">1-Methyl-2-pyrrolidinone (NMP), 99.5%</td>
			<td style="width:160px;">Sigma-Aldrich</td>
			<td style="width:219px;">328634</td>
			<td style="width:63px;"></td>
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			<td height="25" style="height:25px;">Battery test system</td>
			<td style="width:160px;">MACCOR</td>
			<td colspan="2">Series 4000 Automated Test System</td>
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		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Dimethyl carbonate (DMC), &#8805;99%</td>
			<td style="width:160px;">Sigma-Aldrich</td>
			<td style="width:219px;">517127</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Ethyl alcohol, &#8805;99.5%</td>
			<td style="width:160px;">Sigma-Aldrich</td>
			<td style="width:219px;">459844</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Formaldehyde solution, 37 wt. % in H2O</td>
			<td style="width:160px;">Sigma-Aldrich</td>
			<td style="width:219px;">252549</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Graphitized Carbon black, &#62;99.95%</td>
			<td style="width:160px;">Sigma-Aldrich</td>
			<td style="width:219px;">699632</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Iron(III) chloride (FeCl3), 97%</td>
			<td style="width:160px;">Sigma-Aldrich</td>
			<td style="width:219px;">157740</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Kapton polyimide tubing</td>
			<td style="width:160px;">Cole-Parmer</td>
			<td>EW-95820-09</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Kapton polymide tape</td>
			<td style="width:160px;">Cole-Parmer</td>
			<td>EW-08277-80</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">Kapton window film</td>
			<td style="width:160px;">SPEX Sample Prep</td>
			<td style="width:219px;">3511</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Lithium Chip (99.9% Lithium)</td>
			<td style="width:160px;">MTI Corporation</td>
			<td style="width:219px;">EQ-Lib-LiC25</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Lithium trifluoromethanesulfonate (LiCF3SO3)</td>
			<td style="width:160px;">Sigma-Aldrich</td>
			<td style="width:219px;">481548</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Palladium hexafluoroacetylacetonate (Pd(hfac)2), 99.9%</td>
			<td style="width:160px;">Aldrich</td>
			<td style="width:219px;">401471</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Poly(vinylidene fluoride) (PVDF)</td>
			<td style="width:160px;">Aldrich</td>
			<td style="width:219px;">182702</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Potassium permanganate (KMnO4), &#8805;99.0%&#160;</td>
			<td style="width:160px;">Sigma-Aldrich</td>
			<td style="width:219px;">223468</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Sodium hydroxide (NaOH), &#8805;97.0%</td>
			<td style="width:160px;">Sigma-Aldrich</td>
			<td style="width:219px;">221465</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Tetraethylene glycol dimethyl ether (TEGDME), &#8805;99%</td>
			<td style="width:160px;">Aldrich</td>
			<td style="width:219px;">172405</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:388px;">Toray 030 carbon paper</td>
			<td>ElectroChem Inc.</td>
			<td>590637</td>
			<td></td>
		</tr>
	</tbody>
</table>

protocol of electrochemical test and characterization of aprotic li-o2 battery

We demonstrate a method for electrochemical testing of an aprotic Li-O2 battery. An aprotic Li-O2 battery is made of a Li-metal anode, an aprotic electrolyte, and an O2-breathing cathode. The aprotic electrolyte is a solution of lithium salt with aprotic solvent; and porous carbon is commonly used as the cathode substrate. To improve the performance, an electrocatalyst is deposited onto the porous carbon substrate by certain deposition methods, such as atomic layer deposition (ALD) and wet-chemistry reaction. The as-prepared cathode materials are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray absorption near edge structure (XANES). A Swagelok-type cell, sealed in a glass chamber filled with pure O2, is used for the electrochemical test on a battery test system. The cells are tested under either capacity-controlled mode or voltage controlled mode. The reaction products are investigated by electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, and Raman spectroscopy to study the possible pathway of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). This protocol demonstrates a systematic and efficient arrangement of routine tests of the aprotic Li-O2 battery, including the electrochemical test and characterization of battery materials.

Figure 1a shows the setup of the Swagelok-type cell of the Li-O2 battery test. A piece of lithium film is placed on a stainless steel rod at the anode end. The porous cathode is open to pure O2 through an aluminum tube. Glass fiber is used as a separator and an absorber of aprotic electrolyte; and Al-mesh is used as a current-collector. The whole Swagelok-type cell is sealed in a glass chamber filled with ultra-high purity oxygen. For in-depth study, multiple characterization methods are applied to examine the battery system, including the as-prepared electrode materials and the reaction products. SEM and TEM images present the microstructure of the samples. SEM images of the carbon powder before (Figure 1c) and after (Figure 1d) the catalyst loading demonstrate a well preservation of the porous surface structure. TEM images (Figure 1e) shows the electrocatalyst nanoparticles uniformly distribute on the carbon substrate; and well crystallized nanoparticles are shown in the high-resolution TEM image in Figure 1f. Although electron microscopy images show the detail morphology and structure of the electrocatalysts, other X-ray based characterization techniques can provide more information on their chemical composition and valance state. As shown in Figure 1b,13 XANES spectra, which are applied to determine the valence states, show that the electrocatalyst nanoparticles are partly oxidized due to the preparation of cathodes in air.
As-prepared cathode materials are tested in Swagelok-type cells in a voltage window of 2.2-4.5 V (vs Li+/Li). Typical voltage profiles for discharge and discharge-charge cycles are shown in Figure 2a and b. With the presence of the electrocatalyst loaded by ALD, the discharge specific capacity increased to over 4,000 mAh/g when the cell is discharged to 2.2 V, compared to that of the cathode without the electrocatalysts (905 mAh/g). The charge potential reduced to 3.4 V when the cell capacity is controlled at 500 mAh/g (Figure 2b), which are significant improvements comparing with charge potential of 4 V (Figure 2b) for bare carbon cathodes. To better evaluate the battery performance and understand the electrochemical reaction mechanism, the samples at different discharge/charge stages are subjected to the characterization using multiple advanced techniques. In the SEM image of discharged cathode as shown in Figure 2c, the discharge products have the toroidal shape, which are widely accepted as the primary morphology of Li2O2 in a Li-O2 cell.15,52 XRD pattern is used as a direct evidence to identify crystalline products. There are only peaks of Li2O2 and carbon in the XRD pattern of the discharged cathode (Figure 2d), suggesting that the side reactions are minimized in the cell.
XPS and Raman spectra are used to identify the surface composition on electrodes at different charge/discharge status. According to the XPS spectra (Figure 3a), Li2O2 and LiOH form on the cathode surface after discharging; and by charging, Li2O2 is reduced but the irreversible product LiOH remains on the surface. A slight amount of LiO2, an intermediate product of the one-electron transfer ORR, is detected by Raman spectroscopy (Figure 3b). LiO2 is metastable due to its easy disproportionation, which makes only detected by surface-sensitive characterization technique like Raman spectroscopy. The vibration signal of O-H and C=O bond in the FT-IR spectra (Figure 3c and d) indicates the presence of the ether electrolyte as well as other hydroxide, carbonate, or carbonyl species on the surface of Li anode or the glass fiber separator, which form in the side reactions such as the electrolyte decomposition and oxygen crossover effect.
<img alt="Figure 1" src="/files/ftp_upload/53740/53740fig1.jpg" /> 
Figure 1. Swagelok-type cell and as-prepared materials. (a) Schematics of a Swagelok-type cell sealed in a glass chamber. (b) Pd K-edge XANES spectra of the as-prepared cathode material, reprinted from ref. 13. (c, d) SEM images of the carbon powder before and after electrocatalyst loading, respectively. (e, f) TEM and HRTEM images of the carbon powder with electrocatalyst, respectively. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53740/53740fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" src="/files/ftp_upload/53740/53740fig2.jpg" /> 
Figure 2. Voltage Profiles of the discharge/charge process and characterization of the discharged cathodes. (a, b) Voltage profile of a discharge to 2.2 V and a capacity-controlled discharge-charge cycle, respectively. (c, d) SEM image and high-energy XRD pattern of the cathode discharged in Swagelok-type Li-O2 battery, respectively. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53740/53740fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" src="/files/ftp_upload/53740/53740fig3.jpg" /> 
Figure 3. Characterization results. (a) XPS spectra of Li 1s peaks at different charge/ discharge status, reprinted from ref. 13. (b) Raman spectra of the carbon cathodes discharged to 2.5 V. (c, d) FTIR spectra of the anode and separator after discharge-charge cycles, respectively. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53740/53740fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery at JoVE.com

Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery

A protocol for the electrochemical testing of an aprotic Li-O2 battery with the preparation of electrodes and electrolytes and an introduction of the frequently used methods of characterization is presented here.

Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery

We demonstrate a method for electrochemical testing of an aprotic Li-O2 battery. An aprotic Li-O2 battery is made of a Li-metal anode, an aprotic ...

protocol-electrochemical-test-characterization-aprotic-li-o2

Nanyang Technological University

Research

JoVE Journal

Engineering

11.4K Views.  Argonne National Laboratory. A protocol for the electrochemical testing of an aprotic Li-O2 battery with the preparation of electrodes and electrolytes and an introduction of the frequently used methods of characterization is presented here. 

Video: Protocol of Electrochemical Test and Characterization of Aprotic Li-O2 Battery

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Battery safety has been a very important research area over the past decade. Commercially available lithium ion batteries employ low flash point (&lt;80 ...

Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen 1-7. The performance of SOFCs and the rates of many chemical and energy transformation processes in energy storage and conversion devices in general are limited primarily by charge and mass transfer along electrode surfaces and across interfaces. Unfortunately, the mechanistic understanding of these processes is still lacking, due largely to the difficulty of characterizing these processes under in situ conditions. This knowledge gap is a chief obstacle to SOFC commercialization. The development of tools for probing and mapping surface chemistries relevant to electrode reactions is vital to unraveling the mechanisms of surface processes and to achieving rational design of new electrode materials for more efficient energy storage and conversion2. Among the relatively few in situ surface analysis methods, Raman spectroscopy can be performed even with high temperatures and harsh atmospheres, making it ideal for characterizing chemical processes relevant to SOFC anode performance and degradation8-12. It can also be used alongside electrochemical measurements, potentially allowing direct correlation of electrochemistry to surface chemistry in an operating cell. Proper in situ Raman mapping measurements would be useful for pin-pointing important anode reaction mechanisms because of its sensitivity to the relevant species, including anode performance degradation through carbon deposition8, 10, 13, 14 ("coking") and sulfur poisoning11, 15 and the manner in which surface modifications stave off this degradation16. The current work demonstrates significant progress towards this capability. In addition, the family of scanning probe microscopy (SPM) techniques provides a special approach to interrogate the electrode surface with nanoscale resolution. Besides the surface topography that is routinely collected by AFM and STM, other properties such as local electronic states, ion diffusion coefficient and surface potential can also be investigated17-22. In this work, electrochemical measurements, Raman spectroscopy, and SPM were used in conjunction with a novel test electrode platform that consists of a Ni mesh electrode embedded in an yttria-stabilized zirconia (YSZ) electrolyte. Cell performance testing and impedance spectroscopy under fuel containing H2S was characterized, and Raman mapping was used to further elucidate the nature of sulfur poisoning. In situ Raman monitoring was used to investigate coking behavior. Finally, atomic force microscopy (AFM) and electrostatic force microscopy (EFM) were used to further visualize carbon deposition on the nanoscale. From this research, we desire to produce a more complete picture of the SOFC anode.

We present a unique platform for characterizing electrode surfaces in solid oxide fuel cells (SOFCs) that allows simultaneous performance of multiple characterization techniques (e.g. in situ Raman spectroscopy and scanning probe microscopy alongside electrochemical measurements). Complementary information from these analyses may help to advance toward a more profound understanding of electrode reaction and degradation mechanisms, providing insights into rational design of better materials for SOFCs.

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen ...

Fabrication of VB2/Air Cells for Electrochemical Testing

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for synthesizing nanoscopic VB2 is presented as well as step-by-step procedure for applying a zirconium oxide coating to the VB2 particles for stabilization upon discharge. The process for disassembling existing zinc/air cells is shown, in addition construction of the new working electrode to replace the conventional zinc/air cell anode with a the nanoscopic VB2 anode. Finally, discharge of the completed VB2/air battery is reported. We show that using the zinc/air cell as a test bed is useful to provide a consistent configuration to study the performance of the high-energy high capacity nanoscopic VB2 anode.

Fabrication of VB2/Air Cells for Electrochemical Testing

A protocol is presented to study multi-electron metal/air battery systems by using previous technology developed for the zinc/air cell. Electrochemical testing is then performed on fabricated batteries to evaluate performance.

A technique to investigate the properties and performance of new multi-electron metal/air battery systems is proposed and presented. A method for ...

Characterization of Electrode Materials for Lithium Ion and Sodium Ion Batteries Using Synchrotron Radiation Techniques

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. During insertion or removal of alkali metal ions, the redox states of transition metals in the compounds change and structural transformations such as phase transitions and/or lattice parameter increases or decreases occur. These behaviors in turn determine important characteristics of the batteries such as the potential profiles, rate capabilities, and cycle lives. The extremely bright and tunable x-rays produced by synchrotron radiation allow rapid acquisition of high-resolution data that provide information about these processes. Transformations in the bulk materials, such as phase transitions, can be directly observed using X-ray diffraction (XRD), while X-ray absorption spectroscopy (XAS) gives information about the local electronic and geometric structures (e.g.&#160;changes in redox states and bond lengths). In situ experiments carried out on operating cells are particularly useful because they allow direct correlation between the electrochemical and structural properties of the materials. These experiments are time-consuming and can be challenging to design due to the reactivity and air-sensitivity of the alkali metal anodes used in the half-cell configurations, and/or the possibility of signal interference from other cell components and hardware. For these reasons, it is appropriate to carry out ex situ experiments (e.g.&#160;on electrodes harvested from partially charged or cycled cells) in some cases. Here, we present detailed protocols for the preparation of both ex situ and in situ samples for experiments involving synchrotron radiation and demonstrate how these experiments are done.

We describe the use of synchrotron X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) techniques to probe details of intercalation/deintercalation processes in electrode materials for Li-ion and Na-ion batteries. Both in situ and ex situ experiments are used to understand structural behavior relevant to the operation of devices

Intercalation compounds such as transition metal oxides or phosphates are the most commonly used electrode materials in Li-ion and Na-ion batteries. ...

Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. 
Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties.
The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Development of new ablative materials and their numerical modeling requires extensive experimental investigation. This protocol describes procedures for material response characterization in plasma flows with the core techniques being non-intrusive methods to track the material recession along with the chemistry in the reactive boundary layer by emission spectroscopy.

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution ...

Fabrication and Characterization of Superconducting Resonators

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors (MKIDs) for the detection of faint astrophysical signatures, as well as for quantum computing applications and materials characterization. In this paper, procedures are presented for the fabrication and characterization of thin-film superconducting microwave resonators. The fabrication methodology allows for the realization of superconducting transmission-line resonators with features on both sides of an atomically smooth single-crystal silicon dielectric. This work describes the procedure for the installation of resonator devices into a cryogenic microwave testbed and for cool-down below the superconducting transition temperature. The set-up of the cryogenic microwave testbed allows one to do careful measurements of the complex microwave transmission of these resonator devices, enabling the extraction of the properties of the superconducting lines and dielectric substrate (e.g., internal quality factors, loss and kinetic inductance fractions), which are important for device design and performance.

Superconducting microwave resonators are of interest for detection of light, quantum computing applications and materials characterization. This work presents a detailed procedure for fabrication and characterization of superconducting microwave resonator scattering parameters.

Superconducting microwave resonators are of interest for a wide range of applications, including for their use as microwave kinetic inductance detectors ...

Electrochemical Etching and Characterization of Sharp Field Emission Points for Electron Impact Ionization

A new variation of the drop-off method for fabricating field emission points by electrochemically etching tungsten rods in a NaOH solution is described. The results of studies in which the etching current and the molarity of the NaOH solution used in the etching process were varied are presented. The investigation of the geometry of the tips, by imaging them with a scanning electron microscope, and by operating them in field emission mode is also described. The field emission tips produced are intended to be used as an electron beam source for ion production via electron impact ionization of background gas or vapor in Penning trap mass spectrometry applications.

A method for electrochemically etching field emission tips is presented. Etching parameters are characterized and the operation of the tips in field emission mode is investigated.

A new variation of the drop-off method for fabricating field emission points by electrochemically etching tungsten rods in a NaOH solution is described. ...

Fabrication of White Light-emitting Electrochemical Cells with Stable Emission from Exciplexes

The authors present an approach for fabricating stable white light emission from polymer light-emitting electrochemical cells (PLECs) having an active layer which consists of blue-fluorescent poly(9,9-di-n-dodecylfluorenyl-2,7-diyl) (PFD) and &#960;-conjugated triphenylamine molecules. This white light emission originates from exciplexes formed between PFD and amines in electronically excited states. A device containing PFD, 4,4&#39;,4&#39;&#39;-tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA), Poly(ethylene oxide) and K2CF3SO3 showed white light emission with Commission internationale de l&#39;&#233;clairage (CIE) coordinates of (0.33, 0.43) and a Color Rendering Index (CRI) of Ra = 73 at an applied voltage of 3.5 V. Constant voltage measurements showed that the CIE coordinates of (0.27, 0.37), Ra of 67, and the emission color observed immediately after application of a voltage of 5 V were nearly unchanged and stable after 300 sec.

The authors present a method for fabricating stable white-light-emitting electrochemical cells utilizing emission from exciplexes formed between a blue-emitting fluorene polymer and aromatic amines.

The authors present an approach for fabricating stable white light emission from polymer light-emitting electrochemical cells (PLECs) having an active ...

Three-electrode Coin Cell Preparation and Electrodeposition Analytics for Lithium-ion Batteries

As lithium-ion batteries find use in high energy and power applications, such as in electric and hybrid-electric vehicles, monitoring the degradation and subsequent safety issues becomes increasingly important. In a Li-ion cell setup, the voltage measurement across the positive and negative terminals inherently includes the effect of the cathode and anode which are coupled and sum to the total cell performance. Accordingly, the ability to monitor the degradation aspects associated with a specific electrode is extremely difficult because the electrodes are fundamentally coupled. A three-electrode setup can overcome this problem. By introducing a third (reference) electrode, the influence of each electrode can be decoupled, and the electrochemical properties can be measured independently. The reference electrode (RE) must have a stable potential that can then be calibrated against a known reference, for example, lithium metal. The three-electrode cell can be used to run electrochemical tests such as cycling, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). Three-electrode cell EIS measurements can elucidate the contribution of individual electrode impedance to the full cell. In addition, monitoring the anode potential allows the detection of electrodeposition due to lithium plating, which can cause safety concerns. This is especially important for the fast charging of Li-ion batteries in electric vehicles. In order to monitor and characterize the safety and degradation aspects of an electrochemical cell, a three-electrode setup can prove invaluable. This paper aims to provide a guide to constructing a three-electrode coin cell setup using the 2032-coin cell architecture, which is easy to produce, reliable, and cost-effective.

Three-electrode cells are useful in studying the electrochemistry of lithium-ion batteries. Such an electrochemical setup allows the phenomena associated with the cathode and anode to be decoupled and examined independently. Here, we present a guide for construction and use of a three-electrode coin cell with emphasis on lithium plating analytics.

As lithium-ion batteries find use in high energy and power applications, such as in electric and hybrid-electric vehicles, monitoring the degradation and ...

Optimization, Test and Diagnostics of Miniaturized Hall Thrusters

Miniaturized spacecraft and satellites require smart, highly efficient and durable low-thrust thrusters, capable of extended, reliable operation without attendance and adjustment. Thermochemical thrusters which utilize thermodynamic properties of gases as a means of acceleration have physical limitations on their exhaust gas velocity, resulting in low efficiency. Moreover, these engines demonstrate extremely low efficiency at small thrusts and may be unsuitable for continuously operating systems which provide real-time adaptive control of the spacecraft orientation, velocity and position. In contrast, electric propulsion systems which use electromagnetic fields to accelerate ionized gases (i.e., plasmas) do not have any physical limitation in terms of exhaust velocity, allowing virtually any mass efficiency and specific impulse. Low-thrust Hall thrusters have a lifetime of several thousand hours. Their discharge voltage ranges between 100 and 300 V, operating at a nominal power of &lt;1 kW. They vary from 20 to 100 mm in size. Large Hall thrusters can provide fractions of millinewton of thrust. Over the past few decades, there has been an increasing interest in small mass, low power, and high efficiency propulsion systems to drive satellites of 50-200 kg. In this work, we will demonstrate how to build, test, and optimize a small (30 mm) Hall thruster capable of propelling a small satellite weighing about 50 kg. We will show the thruster operating in a large space environment simulator, and describe how thrust is measured and electric parameters, including plasma characteristics, are collected and processed to assess key thruster parameters. We will also demonstrate how the thruster is optimized to make it one of the most efficient small thrusters ever built. We will also address challenges and opportunities presented by new thruster materials.

Here, we present a protocol to test and optimize space propulsion systems based on miniaturized Hall-type thrusters.

Miniaturized spacecraft and satellites require smart, highly efficient and durable low-thrust thrusters, capable of extended, reliable operation without ...