Name: three-electrode coin cell preparation and electrodeposition analytics for lithium-ion batteries
Uploaded: 2018-05-22T15:00:00
Description: Watch this Scientific Journal Video about Three-electrode Coin Cell Preparation and Electrodeposition Analytics for Lithium-ion Batteries at JoVE.com

Financial support from the Texas Instruments (TI) University Research Partnership program is gratefully acknowledged. The authors also gratefully acknowledge the assistance of Chien-Fan Chen from the Energy and Transport Sciences Laboratory, Mechanical Engineering, Texas A&amp;M University, during the initial stage of this work.

1. Reference Electrode and Separator Preparation
<ol>
	<li>Reference electrode preparation
	<ol>
		<li>Wire preparation
		<ol>
			<li>Cut one 120-mm length of size 32 AWG (0.202 mm diameter) enameled copper wire. 
			NOTE: Each wire will become 1 reference electrode and will be used inside 1 three-electrode cell.</li>
			<li>Place one end of the wire in a laboratory press. Gently press approximately 10 mm of wire at one end to a pressure of about 4 MPa. Cut the excess wire off the...

<ol>
	<li>Whittingham, M. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lithium+batteries+and+cathode+materials.">Lithium batteries and cathode materials.</a> Chemical Reviews. 104 (10), 4271-4301 (2004).</li><li>Schipper, F., Aurbach, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Brief+Review:+Past,+Present+and+Future+of+Lithium+Ion+Batteries.">A Brief Review: Past, Present and Future of Lithium Ion Batteries.</a> Russian Journal of Electrochemistry. 52 (12), 1095-1121 (2016).</li><li>Stein, M., Chen, C. F., Robles, D. J., Rhodes, C., Mukherjee, P. 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Q., Prakash, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+a+commercial+size+cylindrical+Li-ion+cell+with+a+reference+electrode.">Characterization of a commercial size cylindrical Li-ion cell with a reference electrode.</a> Journal of Power Sources. 88 (2), 237-242 (2000).</li><li>Wu, M. S., Chiang, P. C. J., Lin, J. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrochemical+investigations+on+advanced+lithium-ion+batteries+by+three-electrode+measurements.">Electrochemical investigations on advanced lithium-ion batteries by three-electrode measurements.</a> Journal of the Electrochemical Society. 152 (1), 47-52 (2005).</li><li>Jansen, A. N., Dees, D. W., Abraham, D. P., Amine, K., Henriksen, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-temperature+study+of+lithium-ion+cells+using+a+LiySn+micro-reference+electrode.">Low-temperature study of lithium-ion cells using a LiySn micro-reference electrode.</a> Journal of Power Sources. 174 (2), 373-379 (2007).</li><li>Belt, J. R., Bernardi, D. M., Utgikar, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+Use+of+a+Lithium-Metal+Reference+Electrode+in+Aging+Studies+of+Lithium-Ion+Batteries.">Development and Use of a Lithium-Metal Reference Electrode in Aging Studies of Lithium-Ion Batteries.</a> Journal of the Electrochemical Society. 161 (6), 1116-1126 (2014).</li><li>McTurk, E., Birkl, C. R., Roberts, M. R., Howey, D. A., Bruce, P. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Minimally+Invasive+Insertion+of+Reference+Electrodes+into+Commercial+Lithium-Ion+Pouch+Cells.">Minimally Invasive Insertion of Reference Electrodes into Commercial Lithium-Ion Pouch Cells.</a> Ecs Electrochemistry Letters. 4 (12), 145-147 (2015).</li><li>Garcia, G., Schuhmann, W., Ventosa, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Three-Electrode,+Battery-Type+Swagelok+Cell+for+the+Evaluation+of+Secondary+Alkaline+Batteries:+The+Case+of+the+Ni-Zn+Battery.">A Three-Electrode, Battery-Type Swagelok Cell for the Evaluation of Secondary Alkaline Batteries: The Case of the Ni-Zn Battery.</a> Chemelectrochem. 3 (4), 592-597 (2016).</li><li>Solchenbach, S., Pritzl, D., Kong, E. J. Y., Landesfeind, J., Gasteiger, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Gold+Micro-Reference+Electrode+for+Impedance+and+Potential+Measurements+in+Lithium+Ion+Batteries.">A Gold Micro-Reference Electrode for Impedance and Potential Measurements in Lithium Ion Batteries.</a> Journal of the Electrochemical Society. 163 (10), 2265-2272 (2016).</li><li>Waldmann, T., 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=Interplay+of+Operational+Parameters+on+Lithium+Deposition+in+Lithium-Ion+Cells:+Systematic+Measurements+with+Reconstructed+3-Electrode+Pouch+Full+Cells.">Interplay of Operational Parameters on Lithium Deposition in Lithium-Ion Cells: Systematic Measurements with Reconstructed 3-Electrode Pouch Full Cells.</a> Journal of the Electrochemical Society. 163 (7), 1232-1238 (2016).</li><li>Costard, J., Ender, M., Weiss, M., Ivers-Tiffee, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-Electrode+Setups+for+Lithium-Ion+Batteries+II.+Experimental+Study+of+Different+Reference+Electrode+Designs+and+Their+Implications+for+Half-Cell+Impedance+Spectra.">Three-Electrode Setups for Lithium-Ion Batteries II. Experimental Study of Different Reference Electrode Designs and Their Implications for Half-Cell Impedance Spectra.</a> Journal of the Electrochemical Society. 164 (2), 80-87 (2017).</li><li>Dees, D. W., Jansen, A. N., Abraham, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Theoretical+examination+of+reference+electrodes+for+lithium-ion+cells.">Theoretical examination of reference electrodes for lithium-ion cells.</a> Journal of Power Sources. 174 (2), 1001-1006 (2007).</li><li>Ender, M., Weber, A., Ivers-Tiffee, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Analysis+of+Three-Electrode+Setups+for+AC-Impedance+Measurements+on+Lithium-Ion+Cells+by+FEM+simulations.">Analysis of Three-Electrode Setups for AC-Impedance Measurements on Lithium-Ion Cells by FEM simulations.</a> Journal of the Electrochemical Society. 159 (2), 128-136 (2012).</li><li>La Mantia, F., Wessells, C. D., Deshazer, H. D., Cui, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reliable+reference+electrodes+for+lithium-ion+batteries.">Reliable reference electrodes for lithium-ion batteries.</a> Electrochemistry Communications. 31, 141-144 (2013).</li><li>Nakahara, K., Nakajima, R., Matsushima, T., Majima, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+particulate+Li4Ti5O12+having+excellent+characteristics+as+an+electrode+active+material+for+power+storage+cells.">Preparation of particulate Li4Ti5O12 having excellent characteristics as an electrode active material for power storage cells.</a> Journal of Power Sources. 117 (1-2), 131-136 (2003).</li><li>Shi, Y., Wen, L., Li, F., Cheng, H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanosized+Li4Ti5O12/graphene+hybrid+materials+with+low+polarization+for+high+rate+lithium+ion+batteries.">Nanosized Li4Ti5O12/graphene hybrid materials with low polarization for high rate lithium ion batteries.</a> Journal of Power Sources. 196 (20), 8610-8617 (2011).</li><li>Dolle, M., Orsini, F., Gozdz, A. S., Tarascon, J. M. <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+reliable+three-electrode+impedance+measurements+in+plastic+Li-ion+batteries.">Development of reliable three-electrode impedance measurements in plastic Li-ion batteries.</a> Journal of the Electrochemical Society. 148 (8), 851-857 (2001).</li><li>Zaghib, K., Simoneau, M., Armand, M., Gauthier, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrochemical+study+of+Li4Ti5O12+as+negative+electrode+for+Li-ion+polymer+rechargeable+batteries.">Electrochemical study of Li4Ti5O12 as negative electrode for Li-ion polymer rechargeable batteries.</a> Journal of Power Sources. 81, 300-305 (1999).</li><li>Delacourt, C., Ridgway, P. 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Cell crimping pressure plays an important part in the success rate of both the preparation and working cells. If the cell is crimped at too high a pressure (&#62;800 psi), the reference electrode can become shorted with the cell cap due to the reference wire position in-between the cap and the gasket. Note that the wire crossing this interface is a requirement in order to connect the reference electrode reading to an external measurement device. If the cell pressure is too low (&#60;700 psi), the cell can have issues wit...

Although the origin of lithium-batteries can be traced arbitrarily far back into the past, the large-scale production and commercialization of many of today&#39;s commonly found lithium-ion batteries began in the 1980s. Many of the materials developed during this era, one example being Lithium Cobalt Oxide (LiCoO2), are still commonly found in use today1. Many current studies have been focused towards the development of various other metal oxide structures, with some emphasis placed towards reducing or eliminating the use of cobalt in place of other lower cost and more environmentally benign metals, such as manganese or nickel2. The continuously changing landscape of materials used in lithium-ion batteries necessitates an effective and accurate method of characterizing both their performance and safety. Because the operation of any battery involves the coupled electrochemical response of both the positive and negative electrodes, typical two electrode batteries fall short of being able to characterize the electrodes independently. Poor characterization and the subsequent lack of understanding may then lead to dangerous situations or poor overall battery performance due to the presence of degradation phenomena. Previous research has been aimed at standardizing the processing techniques for typical two-electrode cells3. One method that improves upon the shortcomings of standard cell configurations is the three-electrode cell.
A three-electrode setup is one method to decouple the two electrodes&#39; responses and provide a greater insight into the fundamental physics of the battery operation. In a three-electrode setup, a reference electrode is introduced in addition to the cathode and anode. This reference electrode is then used to measure the potential of the anode and cathode dynamically during operation. No current is passed through the reference electrode and hence, it provides a singular, and ideally stable, voltage. By using a three-electrode setup, the full cell voltage, the cathode potential, and the anode potential can be collected simultaneously during operation. In addition to potential measurements, the impedance contributions of the electrodes can be characterized as a function of the cell state of charge4.
Three-electrode setups are very useful for studying degradation phenomena in lithium-ion batteries, such as the electrodeposition of lithium metal, also known as lithium plating. Other groups have proposed three-electrode setups5,6,7,8,9,10,11,12,13 but they often use the inherently unstable lithium metal as a reference and include custom, difficult to assemble setups leading to reduced reliability. Lithium plating takes place when instead of intercalating into the host electrode structure, lithium is deposited on the surface of the structure. These deposits commonly assume the morphology of either a (relatively) uniform metallic layer (plating) or small dendritic structures. Plating can have effects ranging from causing safety issues to impeding cycling performance. From a phenomenological perspective, lithium plating occurs due to an inability of lithium to intercalate into the host electrode structure effectively. Plating tends to occur at low temperature, high charging rate, high electrode state of charge (SOC), or a combination of these three factors12. At low temperature, the solid-state diffusion inside the electrode is reduced, due to the Arrhenius diffusivity dependence on temperature. The lower solid-state diffusion results in a buildup of lithium at the electrode-electrolyte interface and a subsequent deposition of lithium. At a high charging rate, a similar phenomenon occurs. The lithium attempts to intercalate into the electrode structure very quickly but is unable to and thus is plated. At a higher SOC, there is on average less available space for the lithium to intercalate into the structure, and thus it becomes more favorable to deposit on the surface.
Lithium dendrites are of particular importance due to the safety concern they cause. If dendrites form inside a cell, there is a potential for them to grow, pierce the separator, and cause an internal short between the anode and cathode. This internal short can lead to very high-localized temperatures in the flammable electrolyte, often resulting in thermal runaway and even in an explosion of the cell. Another issue related to dendrite formation is the increased surface area of the reactive lithium. The newly deposited lithium will react with the electrolyte and cause increased solid electrolyte interphase (SEI) formation, which will lead to increased capacity loss and poor cycling performance.
One issue associated with the design of a three-electrode system is the selection of the appropriate reference electrode. Logistics relating to the location and size of the reference, positive, and negative electrodes can play an important role in acquiring accurate results from the system. One example is that the misalignment of the positive and negative electrodes during the cell construction and the resulting edge effects can introduce error in the reference reading14,15. In terms of material selection, the reference electrode should have a stable and reliable voltage and have a high non-polarizability. Lithium metal, which is often used as a reference electrode by many research groups, has a potential that depends on the passive surface film. This can produce issues because cleaned and aged lithium electrodes display different potentials16. This becomes a problem when long-term aging effects are studied. Research by Solchenbach et al. has attempted to eliminate some of these instability issues by alloying gold with lithium and using it as their reference11. Other research has looked at different materials including lithium titanate, which has been studied experimentally and shows a large electrochemical potential plateau range around 1.5 - 1.6 V17 (~50% SOC). This plateau helps to maintain a stable potential, especially in the event of accidental perturbation to the electrode&#39;s state of charge. The potential stability of LTO, including carbon-based conductive additives, is maintained even at different C-rates and temperatures.18 It is important to emphasize that the selection of the reference electrode is an important step in the three-electrode cell design.
Many research groups have proposed experimental three-electrode cell setup. Dolle et al. used thin plastic cells with a lithium titanate copper wire reference electrode to study changes in impedance due to cycling and storage at high temperatures19. McTurk et al. employed a technique whereby a lithium plated copper wire was inserted into a commercial pouch cell, with the main goal being to demonstrate the importance of noninvasive insertion techniques9. Solchenbach et al. used a modified Swagelok-type T-cell and a gold micro-reference electrode (mentioned earlier) for impedance and potential measurements.11 Waldmann et al. harvested electrodes from commercial cells and reconstructed their own three-electrode pouch cells for use in studying lithium deposition12. Costard et al. developed an in-house experimental three-electrode cell housing to test the effectiveness of different reference electrode materials and configurations13.
Most of these research groups use pure lithium metal as the reference, which can have concerns with stability and SEI growth, especially with long-term use. Other issues involve complicated and time-consuming modifications to existing or commercial setups. In this paper, a reliable and cost-effective technique for constructing three-electrode Li-ion coin cells for electrochemical tests is presented, as shown in Figure 1. This three-electrode setup can be constructed using standard coin cell components, copper wire, and lithium titanate-based reference electrode (see Figure 2). This method does not require any specialized equipment or elaborate modifications and follows standard laboratory scale electrochemical procedures and materials from commercial vendors.

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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Agate Mortar and Pestle</td>
			<td style="width:163px;">VWR</td>
			<td style="width:147px;">89037-492</td>
			<td style="width:565px;">5 in diameter</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Die Set</td>
			<td style="width:163px;">Mayhew</td>
			<td style="width:147px;">66000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Laboratory Press</td>
			<td style="width:163px;">MTI</td>
			<td style="width:147px;">YLJ-12</td>
			<td></td>
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			<td height="21" style="height:21px;width:351px;">Analytical Scale</td>
			<td style="width:163px;">Ohaus</td>
			<td style="width:147px;">Adventurer AX</td>
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			<td height="21" style="height:21px;width:351px;">High-Shear Mixing Device</td>
			<td style="width:163px;">IKA</td>
			<td style="width:147px;">3645000</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Argon-filled Glovebox</td>
			<td style="width:163px;">MBraun</td>
			<td style="width:147px;">LABstar</td>
			<td></td>
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		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Hydraulic Crimper</td>
			<td style="width:163px;">MTI</td>
			<td style="width:147px;">MSK-110</td>
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			<td height="21" style="height:21px;width:351px;">Battery Cycler</td>
			<td style="width:163px;">Arbin Instruments</td>
			<td style="width:147px;">BT2000</td>
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			<td height="21" style="height:21px;width:351px;">Potentiostat/Galvanostat/EIS</td>
			<td style="width:163px;">Bio-Logic</td>
			<td style="width:147px;">VMP3</td>
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			<td height="21" style="height:21px;width:351px;">Vacuum Oven and Pump</td>
			<td style="width:163px;">MTI</td>
			<td style="width:147px;">-</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Copper Wire</td>
			<td style="width:163px;">Remington</td>
			<td style="width:147px;">PN155</td>
			<td>32 AWG</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Glass Balls</td>
			<td style="width:163px;">McMasterr-Carr</td>
			<td style="width:147px;">8996K25</td>
			<td>6 mm borosilicate glass balls</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Stirring Tube</td>
			<td style="width:163px;">IKA</td>
			<td style="width:147px;">3703000</td>
			<td>20 ml</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Celgard 2500 Separator</td>
			<td style="width:163px;">MTI</td>
			<td style="width:147px;">EQ-bsf-0025-60C</td>
			<td>25 &#956;m thick; Polypropylene</td>
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			<td height="21" style="height:21px;width:351px;">Stainless Steel CR2032 Coin Cell Kit</td>
			<td style="width:163px;">Pred Materials</td>
			<td style="width:147px;"></td>
			<td>Coin cell kit includes: case, cap, PP gasket</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Stainless Steel Spacer</td>
			<td style="width:163px;">Pred Materials</td>
			<td style="width:147px;"></td>
			<td>15.5 mm diameter &#215; 0.5 mm thickness</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Stainless Steel Wave Spring</td>
			<td style="width:163px;">Pred Materials</td>
			<td style="width:147px;"></td>
			<td>15.0 mm diameter &#215; 1.4 mm height</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Li-ion Battery Anode - Graphite</td>
			<td style="width:163px;">MTI</td>
			<td>bc-cf-241-ss-005</td>
			<td>Cu Foil Single Side Coated by CMS Graphite (241mm L x 200mm W x 50&#956;m Thickness)</td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:351px;">Li-ion Battery Cathode - LiCoO2</td>
			<td style="width:163px;">MTI</td>
			<td>bc-af-241co-ss-55</td>
			<td>Al Foil Single Side Coated by LiCoO2 (241mm L x 200mm W x 55&#956;m Thickness)</td>
		</tr>
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			<td height="21" style="height:21px;width:351px;">Polyvinylidene Difluoride (PVDF)</td>
			<td style="width:163px;">Kynar</td>
			<td style="width:147px;">Flex 2801</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">N-Methyl-2-Pyrrolidinone Anhydrous (NMP), 99.5%</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:147px;">328634</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">CNERGY Super C-65</td>
			<td style="width:163px;">Timcal</td>
			<td style="width:147px;"></td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:351px;">Electrolyte (1.0 M LiPF6 in EC/DEC, 1:1 by vol.)</td>
			<td style="width:163px;">BASF</td>
			<td style="width:147px;">50316366</td>
			<td></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;width:351px;">Lithium Titanate (Li4Ti5O12)</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:147px;">702277</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">KS6 Synthetic Graphite</td>
			<td style="width:163px;">Timcal</td>
			<td style="width:147px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Lithium Metal Ribbon</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:147px;">320080</td>
			<td>0.75 mm thickness</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Epoxy Multipurpose</td>
			<td style="width:163px;">Loctite</td>
			<td style="width:147px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Electrical Tape</td>
			<td style="width:163px;">Scotch 3M Super 88&#160;</td>
			<td style="width:147px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:351px;">Isopropyl Alcohol (IPA), ACS reagent, &#8805;99.5%</td>
			<td style="width:163px;">Sigma Aldrich</td>
			<td style="width:147px;">190764</td>
			<td></td>
		</tr>
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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.

Typical results for the voltage and potential profiles for the three-electrode cell can be seen in Figure 7. In an ideal setup, the full cell voltage should be identical to that produced from a two-electrode cell using the same electrode couple. This is one method to determine whether the insertion of the reference electrode modifies the performance of the cell. If there is a significant difference between the two- and three-electrode full cell performance (f...

Watch this Scientific Journal Video about Three-electrode Coin Cell Preparation and Electrodeposition Analytics for Lithium-ion Batteries at JoVE.com

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

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 ...

The overall goal of this study is to demonstrate construction of a reliable three-electrode coin cell setup to investigate degradation phenomena in lithium-ion cells while simultaneously identifying the influence of the anode and cathode. This method can help answer key questions in the energy storage and scepter field, such what's the role of anode and cathode in the lithium-ion cells's degradation phenomena. The main advantage of this technique is that cell construction simplicity, along with the measurement reliability, of electrochemical properties.The implications of this technique extend toward monitoring the electrochemical characteristics of anode and cathode separately during charge and discharge process due to the presence of the reference electrode. Construct the reference electrode with enameled copper wire. Cut a 120 millimeter-length wire for each three-electrode cell.Place one end of wire about ten millimeters into a lab press and apply four megapascals of pressure. After removing the wire, cut it so the flattened section is about two millimeters long. Next, carefully use a scalpel to remove the outer insulation on the flattened end.Put the wire aside and move on to make the slurry. Obtain a solution of 10%weight PVDF and NMP. Separately weigh out and add to the same mortar lithium titanate powder, synthetic graphite, and a conductive additive.Mix and grind the powders until the mixture is homogenous. Next, transfer the powder mix to a 20 milliliter disposable mixing tube. Then, use a pipette to add NMP solution.Continue by adding 16 six millimeter diameter silicate glass mixing balls before screwing on the cap. Use a high sheer mixing device to mix the slurry. After mixing, work with the slurry and the previously-prepared exposed wire.By hand, dip the exposed copper tip into the mixed slurry. On removal, attach the wires to a base, cast end up, to dry. Dry the electrodes in a laboratory oven at 70 degrees Celsius for at least eight hours.When all of the components and electrolyte are ready, put them in an argon glove box. Here are the case and cap, gasket, polypropylene separators, stainless steel spacer, and wave spring. Have the reference electrode bent into a spiral shape using pliers.Inside the glove box, prepare two clean disks of lithium. Get one disk of lithium and a stainless steel spacer. Place the lithium disk at the center of the spacer and then press the two together firmly.Check that the lithium sticks to the spacer. Now, work with the coin cell case and a small weigh boat and center the second lithium disk inside the case. Press it firmly and ensure that it sticks.Place several drops of electrolyte on the lithium disk. Place several more drops around the edge of the lithium to fill the outside gap. Next, place a polypropylene separator on top of the wetted lithium disk.When the separator is completely wetted, place the gasket in the cell with its lip facing upwards. Use a pair of plastic tweezers to gently place the reference electrode spiral in the cell's center. Add a few drops of electrolyte around the reference electrode.Then, place a small square separator where the wire crosses over the gasket and case. Continue by placing a polypropylene separator on top of the reference electrode. Retrieve the lithium spacer disk and put it on top of the assembly, lithium side down.Next, place the wave spring on top of the spacer. Then, use plastic tweezers to carefully place the cap on the entire assembly. Employ a crimper to crimp the coin cell to about five megapascals.At this point, the cell can be removed from the glove box. Clean and dry the cell before going on. To seal it, use a toothpick to apply a small amount of non-conductive epoxy where the wire exits the coin cell.For lithiation, set up the testing device. Place a small square of electrical tape across the top of the coin cell case and place it in the cell holder. Use an alligator clip to connect the reference electrode to the cell holder's positive connection.Cycle the reference electrode several times at the appropriate voltage range. Take note of the reference voltage, which should occur during charging and discharging processes. Return the cell to the argon glove box equipped with the materials to make a working cell.Place the cathode disk in the center of the cell case. Then, put several drops of the electrolyte onto the top and around the edge. Next, place a separator on top of the wetted electrode.On top of that, place the gasket with the lip facing up. Put the assembly aside and get the lithiated preparation cell. Apply electrical tape on the case top and hold it with thin-nosed pliers.Use cutting-end pliers to carefully yet firmly pry open the edge of the coin cell. When it is possible, separate the cell case and cap and carefully extract the lithiated reference electrode. With a pair of pliers, unbend the spiral of the reference electrode and straighten it.Bring the working cell and the reference electrode together. Place the reference electrode's tip in the center of the working electrode. It will extend over the edge of the cell.Re-bend the wire at the edge of the cell and place a small rectangular separator where the wire crosses the case. Next, position a separator on top of the reference electrode. Top this with the prepared anode disk.Carefully place a one millimeter stainless steel spacer on the anode. Then, place the wave spring on the assembly. Now, fill the cell to the brim with electrolyte.Use plastic tweezers to carefully place the cell cap on the assembly. Transfer the cell to a crimper and crimp the cell to five megapascals. After removing the cell from the argon box, clean and seal it.Allow the completed cell to dry for at least one hour. Take the cell to an electrochemical measuring device. Connect the cell as in this schematic.The positive power and positive sensor connect to the cathode. The negative power and sensor connect to the anode. The reference connects to the reference electrode.Cycle the full cell at the desired C rate and simultaneously measure full cell cathode and anode potentials. Move the cell to the electrochemical impedance spectroscopy device. Connect the positive power and sensor to the cell's cathode and the negative power and sensor and reference sensor to the anode.Keep the reference electrode disconnected. On the control panel, select an amplitude of ten millivolts. Select the frequency range of one megahertz to one millihertz.Start collecting the impedance of the full cell. Here are the voltage measurements at constant current for an anode, using the scale on the right, and a cathode, and both a two-and three-electrode full cell using the scale on the left. The charging rate is 1/10th the calculated maximum.The full cell voltages for the two-and three-electrode cells are the same, suggesting that the reference electrode does not modify behavior. Compare these with voltage measurements during discharge. During charging, the cathode potential increases with respect to lithium slash lithium plus as lithium moves from the cathode to the anode.The potential at the anode decreases. The voltage measurements during discharge demonstrate the opposite occurs under those conditions. This is an example of the impedance spectrum collected for the three-electrode full cell as a function of the state of charge.Here are additional spectra for the cathode and anode. The data are useful in finding individual contributions to the electrode impedance as the state of charge changes. Once mastered, this technique can be done in five days, including cycling and impedance tests, if it's performed properly.While attempting this procedure, it's important to remember that the reference electrode wire is thin, and can break if not handled properly. Following this procedure, fast-charting and safety tests can be performed in order to answer questions like Is it possible to fast-chart a cell without inducing any degradation? And What's the role anode and cathode on failure events?After its development, this technique paved the way for researchers in the field of energy storage to diagnose failure and improve the lifetime of lithium ion batteries. After watching this video, you should have a good understanding of how to build a stable and reliable three-electrode cell using typical components found in any electrochemical lab. Don't forget that working with lithium compounds, organic electrolytes, and electrical equipment can be extremely hazardous, and precautions, such as using personal protective equipment, should always be taken while performing this procedure.

three-electrode-coin-cell-preparation-electrodeposition-analytics-for

Research

JoVE Journal

Engineering

Construction and Testing of Coin Cells of Lithium Ion Batteries

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime. Lithium ion batteries have also been considered to be used in electric and hybrid vehicles1 or even electrical grid stabilization systems2. All these applications simulate a dramatic increase in the research and development of battery materials3-7, including new materials3,8, doping9, nanostructuring10-13, coatings or surface modifications14-17 and novel binders18. Consequently, an increasing number of physicists, chemists and materials scientists have recently ventured into this area. Coin cells are widely used in research laboratories to test new battery materials; even for the research and development that target large-scale and high-power applications, small coin cells are often used to test the capacities and rate capabilities of new materials in the initial stage. 
 In 2010, we started a National Science Foundation (NSF) sponsored research project to investigate the surface adsorption and disordering in battery materials (grant no. DMR-1006515). In the initial stage of this project, we have struggled to learn the techniques of assembling and testing coin cells, which cannot be achieved without numerous help of other researchers in other universities (through frequent calls, email exchanges and two site visits). Thus, we feel that it is beneficial to document, by both text and video, a protocol of assembling and testing a coin cell, which will help other new researchers in this field. This effort represents the "Broader Impact" activities of our NSF project, and it will also help to educate and inspire students.
In this video article, we document a protocol to assemble a CR2032 coin cell with a LiCoO2 working electrode, a Li counter electrode, and (the mostly commonly used) polyvinylidene fluoride (PVDF) binder. To ensure new learners to readily repeat the protocol, we keep the protocol as specific and explicit as we can. However, it is important to note that in specific research and development work, many parameters adopted here can be varied. First, one can make coin cells of different sizes and test the working electrode against a counter electrode other than Li. Second, the amounts of C black and binder added into the working electrodes are often varied to suit the particular purpose of research; for example, large amounts of C black or even inert powder were added to the working electrode to test the "intrinsic" performance of cathode materials14. Third, better binders (other than PVDF) have also developed and used18. Finally, other types of electrolytes (instead of LiPF6) can also be used; in fact, certain high-voltage electrode materials will require the uses of special electrolytes7.

A protocol to construct and test coin cells of lithium ion batteries is described. The specific procedures of making a working electrode, preparing a counter electrode, assembling a cell inside a glovebox and testing the cell are presented.

Rechargeable lithium ion batteries have wide applications in electronics, where customers always demand more capacity and longer lifetime.  Lithium ion ...

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. ...

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and reduction half reactions, and fast electron (hole) diffusion and charge separation. Nanowires present suitable architectures to meet these requirements. Axially segmented Ag|ZnO and radially segmented (coaxial) TiO2-Ag nanowires with a diameter of 200 nm and a length of 6-20 &#181;m were made by templated electrodeposition within the pores of polycarbonate track-etched (PCTE) or anodized aluminum oxide (AAO) membranes, respectively. In the photocatalytic experiments, the ZnO and TiO2 phases acted as photoanodes, and Ag as cathode. No external circuit is needed to connect both electrodes, which is a key advantage over conventional photo-electrochemical cells. For making segmented Ag|ZnO nanowires, the Ag salt electrolyte was replaced after formation of the Ag segment to form a ZnO segment attached to the Ag segment. For making coaxial TiO2-Ag nanowires, a TiO2 gel was first formed by the electrochemically induced sol-gel method. Drying and thermal annealing of the as-formed TiO2 gel resulted in the formation of crystalline TiO2 nanotubes. A subsequent Ag electrodeposition step inside the TiO2 nanotubes resulted in formation of coaxial TiO2-Ag nanowires. Due to the combination of an n-type semiconductor (ZnO or TiO2) and a metal (Ag) within the same nanowire, a Schottky barrier was created at the interface between the phases. To demonstrate the photocatalytic activity of these nanowires, the Ag|ZnO nanowires were used in a photocatalytic experiment in which H2 gas was detected upon UV illumination of the nanowires dispersed in a methanol/water mixture. After 17 min&#160;of illumination, approximately 0.2 vol% H2 gas was detected from a suspension of ~0.1 g of Ag|ZnO nanowires in a 50 ml 80 vol% aqueous methanol solution.

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

Procedures are outlined to prepare segmented and coaxial nanowires via templated electrodeposition in nanopores. As examples, segmented nanowires consisting of Ag and ZnO segments, and coaxial nanowires consisting of a TiO2 shell and a Ag core were made. The nanowires were used in photocatalytic hydrogen formation experiments.

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and ...

The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and polar dielectric liquids. These bridges are unique from capillary bridges in that they exhibit extensibility beyond a few millimeters, have complex bi-directional mass transfer patterns, and emit non-Planck infrared radiation. A number of common solvents can form such bridges as well as low conductivity solutions and colloidal suspensions. The macroscopic behavior is governed by electrohydrodynamics and provides a means of studying fluid flow phenomena without the presence of rigid walls. Prior to the onset of a liquid bridge several important phenomena can be observed including advancing meniscus height (electrowetting), bulk fluid circulation (the Sumoto effect), and the ejection of charged droplets (electrospray). The interaction between surface, polarization, and displacement forces can be directly examined by varying applied voltage and bridge length. The electric field, assisted by gravity, stabilizes the liquid bridge against Rayleigh-Plateau instabilities. Construction of basic apparatus for both vertical and horizontal orientation along with operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

Horizontal and vertical electrohydrodynamic liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields and polar dielectric liquids. The construction of basic apparatus and operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and ...

In Situ Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries

Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric vehicles.1,2 However, many challenges, such as energy density and battery lifetimes, need to be overcome before this particular battery technology can be widely implemented in such applications.3 This research is challenging, and we outline a method to address these challenges using in situ NPD to probe the crystal structure of electrodes undergoing electrochemical cycling (charge/discharge) in a battery. NPD data help determine the underlying structural mechanism responsible for a range of electrode properties, and this information can direct the development of better electrodes and batteries.
We briefly review six types of battery designs custom-made for NPD experiments and detail the method to construct the &#8216;roll-over&#8217; cell that we have successfully used on the high-intensity NPD instrument, WOMBAT, at the Australian Nuclear Science and Technology Organisation (ANSTO). The design considerations and materials used for cell construction are discussed in conjunction with aspects of the actual in situ NPD experiment and initial directions are presented on how to analyze such complex in situ data.

In Situ Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries

We describe the design and construction of an electrochemical cell for the examination of electrode materials using in situ neutron powder diffraction (NPD). We briefly comment on alternate in situ NPD cell designs and discuss methods for the analysis of the corresponding in situ NPD data produced using this cell.

Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric ...

Failure Analysis of Batteries Using Synchrotron-based Hard X-ray Microtomography

Imaging morphological changes that occur during the lifetime of rechargeable batteries is necessary to understand how these devices fail. Since the advent of lithium-ion batteries, researchers have known that the lithium metal anode has the highest theoretical energy density of any anode material. However, rechargeable batteries containing a lithium metal anode are not widely used in consumer products because the growth of lithium dendrites from the anode upon charging of the battery causes premature cell failure by short circuit. Lithium dendrites can also form in commercial lithium-ion batteries with graphite anodes if they are improperly charged. We demonstrate that lithium dendrite growth can be studied using synchrotron-based hard X-ray microtomography. This non-destructive imaging technique allows researchers to study the growth of lithium dendrites, in addition to other morphological changes inside batteries, and subsequently develop methods to extend battery life.

Synchrotron-based hard X-ray microtomography is used to image the electrochemical growth of dendrites from a lithium metal electrode through a solid polymer electrolyte membrane.

Imaging morphological changes that occur during the lifetime of rechargeable batteries is necessary to understand how these devices fail. Since the advent ...

Non-aqueous Electrode Processing and Construction of Lithium-ion Coin Cells

Research into new and improved materials to be utilized in lithium-ion batteries (LIB) necessitates an experimental counterpart to any computational analysis. Testing of lithium-ion batteries in an academic setting has taken on several forms, but at the most basic level lies the coin cell construction. In traditional LIB electrode preparation, a multi-phase slurry composed of active material, binder, and conductive additive is cast out onto a substrate. An electrode disc can then be punched from the dried sheet and used in the construction of a coin cell for electrochemical evaluation. Utilization of the potential of the active material in a battery is critically dependent on the microstructure of the electrode, as an appropriate distribution of the primary components are crucial to ensuring optimal electrical conductivity, porosity, and tortuosity, such that electrochemical and transport interaction is optimized. Processing steps ranging from the combination of dry powder, wet mixing, and drying can all critically affect multi-phase interactions that influence the microstructure formation. Electrochemical probing necessitates the construction of electrodes and coin cells with the utmost care and precision. This paper aims at providing a step-by-step guide of non-aqueous electrode processing and coin cell construction for lithium-ion batteries within an academic setting and with emphasis on deciphering the influence of drying and calendaring.

Non-aqueous electrode processing is central to the construction of coin cells and the evaluation of new electrode chemistries for lithium-ion batteries. A step-by-step guide to the basic practices needed as an electrochemical engineer working with batteries in an academic experimental setting is furnished.

Research into new and improved materials to be utilized in lithium-ion batteries (LIB) necessitates an experimental counterpart to any computational ...

Synthesis of Ionic Liquid Based Electrolytes, Assembly of Li-ion Batteries, and Measurements of Performance at High Temperature

The chemical instability of the traditional electrolyte remains a safety issue in widely used energy storage devices such as Li-ion batteries. Li-ion batteries for use in devices operating at elevated temperatures require thermally stable and non-flammable electrolytes. Ionic liquids (ILs), which are non-flammable, non-volatile, thermally stable molten salts, are an ideal replacement for flammable and low boiling point organic solvent electrolytes currently used today. We herein describe the procedures to: 1) synthesize mono- and di-phosphonium ionic liquids paired with chloride or bis(trifluoromethane)sulfonimide (TFSI) anions; 2) measure the thermal properties and stability of these ionic liquids by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA); 3) measure the electrochemical properties of the ionic liquids by cyclic voltammetry (CV); 4) prepare electrolytes containing lithium bis(trifluoromethane)sulfonamide; 5) measure the conductivity of the electrolytes as a function of temperature; 6) assemble a coin cell battery with two of the electrolytes along with a Li metal anode and LiCoO2 cathode; and 7) evaluate battery performance at 100 &#176;C. We additionally describe the challenges in execution as well as the insights gained from performing these experiments.

Here, we describe protocols to prepare phosphonium-based ionic liquid and lithium bis(trifluoromethane)sulfonimide salt electrolytes, and assemble a non-flammable and high temperature functioning lithium-ion coin cell battery.

The chemical instability of the traditional electrolyte remains a safety issue in widely used energy storage devices such as Li-ion batteries. Li-ion ...

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of lithium-ion (Li-ion) batteries. However, a number of setbacks prevent their integration into commercial devices. The main limiting factor is due to nanoscale phenomena occurring at the electrode/electrolyte interfaces, ultimately leading to degradation of battery operation. These key problems are highly challenging to observe and characterize as these batteries contain multiple buried interfaces. One approach for direct observation of interfacial phenomena in thin film batteries is through the fabrication of electrochemically active nanobatteries by a focused ion beam (FIB). As such, a reliable technique to fabricate nanobatteries was developed and demonstrated in recent work. Herein, a detailed protocol with a step-by-step process is presented to enable the reproduction of this nanobattery fabrication process. In particular, this technique was applied to a thin film battery consisting of LiCoO2/LiPON/a-Si, and has further been previously demonstrated by in situ cycling within a transmission electron microscope.

Focused Ion Beam Fabrication of LiPON-based Solid-state Lithium-ion Nanobatteries for In Situ Testing

A protocol for the fabrication of electrochemically active LiPON-based solid-state lithium-ion nanobatteries using a focused ion beam is presented.

Solid-state electrolytes are a promising replacement for current organic liquid electrolytes, enabling higher energy densities and improved safety of ...

Preparation of Liquid Crystal Networks for Macroscopic Oscillatory Motion Induced by Light

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous light irradiation. The photo-excitation of dopants that can quickly dissipate light into heat, coupled with anisotropic thermal expansion and self-shadowing of the film, gives rise to the self-sustained deformation. The oscillations observed are influenced by the dimensions and the modulus of the film, and by the directionality and intensity of the light. The system developed offers applications in energy conversion and harvesting for soft-robotics and automated systems.
The general method described here consists of creating free-standing liquid crystalline films and characterizing the mechanical and thermal effects observed. The molecular alignment is achieved using alignment layers (rubbed polyimide), commonly used in the display manufacturing industry. To obtain actuators with large deformation, the mesogens are aligned and polymerized in a splay/bend configuration, i.e., with the director of the liquid crystals (LCs) going gradually from planar to homeotropic through the film thickness. Upon irradiation, the mechanical and thermal oscillations obtained are monitored with a high-speed camera. The results are further quantified by image analysis using an image processing program.

The goal of the protocol is to create liquid crystalline polymer films that can mechanically oscillate under continuous light irradiation. We describe in great detail the conception of free-standing films, from the liquid crystal alignment method to the photo-actuation. The experimental protocol applied to prepare this material is broadly applicable.

A strategy based on doped liquid crystalline networks is described to create mechanical self-sustained oscillations of plastic films under continuous ...