This article was supported in part by BU and by the Advanced Energy Consortium:

1.Synthesis of Mono- and Di-phosphonium Ionic Liquids Paired with Chloride (Cl) and Bis(trifluoromethane)sulfonimide (TFSI) Anions
NOTE: The procedure for the mono-phosphonium ionic liquid possessing three hexyl and one decyl alkyl chain surrounding the phosphonium cation is described, and this ionic liquid is abbreviated as mono-HexC10Cl. The same procedure is repeated using 1,10-dichlorodecane to obtain the di-phosphonium ionic liquid in high yield, and this ionic liquid is abbreviated as di-HexC10Cl.
<ol>
	<li>While in a glove box under argon, weigh out trihexylphosphine (8.3 g, 29 mmol) using a glass pipet, and dispense into a heavy wall pressure vessel. Next, add 1-chlorodecane (5.22 g, 29.6 mmol) using a glass pipet to the same vessel. Cap the vessel containing the mixture with a PTFE bushing.</li>
	<li>Heat the resulting mixture under argon to 140 &#176;C for 24 hr while mixing to obtain the mono-HexC10Cl. The mixture will become viscous.</li>
	<li>Place the mixture under high vacuum at 140 &#176;C while stirring to remove any remaining volatile starting materials to obtain the crude mono-HexC10Cl.
	<ol>
		<li>To purify, extract the mono-HexC10Cl from the crude mixture using approximately 10 ml of a 1:1 dichloromethane (DCM) to saturated sodium chloride solution (brine) in a 250 ml separatory funnel. Collect the DCM phase. Repeat the extraction process three times.</li>
		<li>Combine the 15 ml of collected DCM solutions containing the product, and evaporate the solvent using a rotary evaporator to obtain the mono-HexC10Cl product.</li>
	</ol>
	</li>
	<li>Dissolve the mono-HexC10Cl (7.75 g, 16.74 mmol) in 10 ml of DCM and add LiTFSI (6.25 g, 21.76 mmol), pre-dissolved in 10 ml of deionized water. Cap the resulting mixture and stir it at room temperature for 24 hours.</li>
	<li>Extract the mono-HexC10TFSI from the mixture using a 250 ml separatory funnel filled with approximately 20 ml of DCM. Repeat the extraction process three times. Combine the DCM solutions.</li>
	<li>Add 1-2 drops of 1 N AgNO3 solution to 1 ml of&#160;the DCM phase to confirm the complete elimination of chloride anions from the organic phase. A white precipitate will be produced if chloride anions remain in solution. Repeat the extraction step until no white precipitate is produced.</li>
	<li>Add 1 g of anhydrous MgSO4 to the DCM solution, stir the mixture, and then decant the dried DCM solution. Next, evaporate the solvent by rotary evaporation. The yield is typically greater than 98%.</li>
	<li>Repeat the same procedure using 1,10-dichlorodecane to obtain the two di-phosphonium ionic liquids, di-HexC10Cl and di-HexC10TFSI, in high yield.</li>
	<li>Characterize the ionic liquids using 1H, 13C, and 19F NMR in deuterated-chloroform (shift 7.24) and submit the samples for elemental analysis and mass spectrometry analysis.</li>
</ol>
2. Characterization of the Ionic Liquids
<ol>
	<li>Differential scanning calorimetry (DSC)
	<ol>
		<li>Weigh out 5 to 10 mg of the ionic liquid (record the actual mass) and add it to the center of an aluminum sample pan, which is subsequently hermetically sealed. Be sure to complete this step efficiently as the ionic liquids are hydroscopic and the weight will change if left to stand.</li>
		<li>Load the sample pan and an unloaded (reference) pan into the differential scanning calorimeter. Be sure to place the sample and reference pan in the appropriate location as determined by the specific DSC used.</li>
		<li>Program a temperature ramp and cooling cycle: 1) heat from -70 &#176;C to 200 &#176;C at a heating rate of 10 &#176;C/min, 2) cool to -70 &#176;C at a cooling rate of 5 &#176;C/min, and 3) repeat the heat-cool cycling three times.</li>
		<li>By analyzing the thermal trace, determine the melting point (Tm), crystallization (Tc) and glass transition temperatures (Tg) (if applicable).</li>
	</ol>
	</li>
	<li>Thermal gravimetric analysis (TGA)
	<ol>
		<li>Clean and tare the platinum pan on the movable arm of the TGA. Add 5 to 10 mg of the ionic liquid on the pan. Only touch the pan using tweezers.</li>
		<li>Heat the sample from 20 to 500 &#176;C at a heating rate of 10 &#176;C/min.</li>
		<li>Identify the decomposition temperature where 10% of the original sample weight is lost. For long-term stability studies, heat the sample at a set temperature for a prolonged time and monitor the loss of weight.</li>
	</ol>
	</li>
	<li>Viscosity measurements
	<ol>
		<li>With a glass pipette, place 1 ml of ionic liquid on the Peltier stage of a controlled strain rheometer. Make sure the aluminum plate is fully covered with the ionic liquid.</li>
		<li>Use a 20 mm diameter parallel aluminum plate (or cone) and set the gap between the aluminum plate and the top surface of the sample to be 1.0 - 2.0 mm in all of the runs.</li>
		<li>To minimize the effect of moisture in the air, perform the measurements in a glove bag filled with nitrogen gas.</li>
		<li>Prior to each test, pre-shear the sample at a shear rate of 100 Hz for 10 sec to eliminate any physical memory of the sample, follow with a 15 min equilibrium step in order for the sample to reach a steady state condition.</li>
		<li>Determine the linear viscoelastic region (LVR) via an oscillatory strain sweep at a fixed frequency (1 Hz) with a strain amplitude from 0.1 to 10%.</li>
		<li>Select a strain that lies in the LVR and perform the oscillatory frequency sweep from 0.1 to 10 Hz. Determine the complex viscosity at a particular frequency and strain.</li>
		<li>Perform an oscillatory temperature sweep controlled by the instrument software from 10 &#176;C to 95 &#176;C with increments of 5 &#176;C and a 1 min equilibrium at each temperature. Define strain and frequency, for example, to be 1.0% and 1 Hz, respectively. Complex viscosities at different temperatures are read out.</li>
	</ol>
	</li>
	<li>Conductivity measurements
	<ol>
		<li>Dry the ionic liquid at 100 &#176;C under high vacuum for 12 hr to remove trace amounts of moisture before testing.</li>
		<li>In a glove box under an argon atmosphere, load approximately 4 ml of the sample in a test tube, be sure to add enough sample to immerse the sensing tape of the conductivity probe completely.</li>
		<li>Use a heating block to control the temperature and maintain the stirring during the measurement to maintain homogeneity.</li>
		<li>Read the conductivity at each temperature after a 30 min equilibration time.</li>
	</ol>
	</li>
	<li>Cyclic voltammetry (CV)
	<ol>
		<li>Assemble a lithium/lithium/platinum three-electrode system in the glove box under an argon atmosphere.</li>
		<li>Charge the vessel with the ionic liquid and make sure all the electrodes are immersed in the ionic liquid. Seal the vessel under argon.</li>
		<li>Equilibrate the vessel at the desired temperature for 20 min. Sweep the potential rate at 1 mV/sec between &#8722;0.2 V and 6.5 V versus Li+/Li.</li>
	</ol>
	</li>
</ol>
3. Preparation of the Electrolytes
<ol>
	<li>Dry the ionic liquid under high vacuum at 80 &#176;C overnight with rigorous stirring to ensure removal of trace amounts of water.</li>
	<li>Dry the LiTFSI at 70 &#176;C for three days in a vacuum oven.</li>
	<li>Transfer the anhydrous ionic liquid and LiTFSI salt to the glove box.</li>
	<li>Add the ionic liquid (e.g., mono-HexC10TFSI, 4.50 g, 6.4 mmol) and LiTFSI (1.83 g, 6.4 mmol) to an oven-dried flask containing a stir bar. Stir the mixture overnight until it is homogeneous to obtain a concentration of 1.6 M for the electrolyte.</li>
</ol>
4. Fabrication of the Lithium Ion Coin Cell Battery
<ol>
	<li>In the glove box under argon atmosphere, place one spring and one stainless steel disc in the bottom cap of the coin cell. Place a 12.7 mm diameter LiCoO2 electrode (24 mg) in the stainless steel disc.</li>
	<li>Soak two pieces of the separators (porous polypropylene membranes) in the above-prepared ionic liquid electrolyte at 60 &#176;C on a hot plate for 15 min.</li>
	<li>Add the ionic liquid electrolyte to the surface of the LiCoO2 cathode until the material is fully covered with electrolyte (&#8776; 0.5 ml).</li>
	<li>Place the separators soaked in the electrolyte in the center of the coin cell. Then add a few more drops of ionic liquid electrolyte (a few microliters) onto the separators.</li>
	<li>Cut a piece of lithium metal with a diameter of 12.7 mm in the glove box. Place the lithium metal on top of the separators.</li>
	<li>Cap the coin cell and seal it with a crimper in the glove box.</li>
	<li>Transfer the coin cell out of the glove box and rest the cell for 12 hr prior to initiating the battery/electrochemical tests.</li>
</ol>
5. Performance of the Battery at 100 &#176;C
<ol>
	<li>Place the coin cell in an oven operating at 100 &#176;C, which has a small hole in the back wall where the cables from the electrochemical testing station have been threaded. Connect the coin cell to the electrochemical testing station.</li>
	<li>Leave the cell at 100 &#176;C for 30 min to equilibrate to the temperature.</li>
	<li>Select galvanostatic charge-discharge cycling on the electrochemical testing station. Set the cycle number to 500.</li>
	<li>Set the charge current to 500 &#181;A and the voltage upper limit to 4.2 V. Set a rest time of 60 sec at 0 V after each charge.</li>
	<li>Set the discharge current to 500 &#181;A and the voltage lower limit to 3.0 V. Set a rest time of 60 sec at 0 V after each discharge.</li>
	<li>Start the charge-discharge cycling at a current of 500 &#181;A between 3.0 V to 4.2 V using the software. Evaluate the charge output against time.</li>
</ol>

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The authors declare that they have no competing financial interests.

Our approach to develop non-flammable and high temperature functional Li-ion batteries involves the synthesis of new ionic liquid electrolytes and their subsequent evaluation in prototypical coin cells. Specifically, mono-HexC10TFSI and di-HexC10TFSI based electrolytes were tested in a coin cell possessing a Li metal anode and LiCoO2 cathode. The critical steps within this approach are to: 1) identify the lead electrolyte according to a set of design specifications; 2) maintain dryness and ensure water does no...

Li-ion batteries are devices that transform energy between electrical energy and chemical energy and provide a convenient means to store and to deliver energy on demand and on-the-go. Today, Li-ion batteries dominate the portable electronics market because of their high energy density and re-chargeability, and are of interest for large-scale and specialty applications, such as down-hole drilling and automotive.1-5 Batteries are composed of four primary components: cathode, anode, separator, and electrolyte. While the chemistry of the two electrodes dictates the theoretical energy density of the battery, the safety and working temperature are mainly limited by the electrolyte material.6-9 Carbonate based organic solvent electrolytes (e.g., dimethyl carbonate (DMC) and ethylene carbonate (EC)) are widely used in Li-ion batteries due to their low viscosity, high conductivity, and high lithium salt solubility. Moreover, certain combinations of the carbonate solvents (DMC/EC) also form a stable solid electrolyte interface (SEI), thereby preventing degradation reactions between the electrolyte and the electrode, and extending battery life. However, carbonate solvents suffer from low boiling points and flash points, limiting the operation temperature of Li-ion batteries to below 55 &#176;C, with potentially severe safety issues when there is a short-circuit.10,11
Ionic liquids are a class of salts that have melting temperatures below 100 &#176;C.12 In contrast to typical inorganic salts, ionic liquids possess a wide liquid range and can be liquid at room temperature. Ionic liquids are composed of one or multiple organic cationic centers, such as imidazolium, phosphonium, pyridinium, or ammonium and paired with an inorganic or organic anion, such as methansulfonate, hexafluorophosphate, or halide.13,14 The wide variety of possible cation and anion combinations allows for a large number of compositions with tunable properties. In addition, the strong ionic interactions within ionic liquids result in negligible vapor pressure, non-flammability, and high thermal and electrochemical stability.15,16
Replacing conventional electrolytes with ionic liquids is one solution that addresses the inherent safety issues in current Li-ion batteries, and could enable high temperature applications.17-27 To illustrate the general synthetic and material processing methods utilized to construct lithium ion batteries containing ionic liquids for high temperature applications, we describe the synthesis, thermal properties, and electrochemical characterization of mono- and di-phosphonium ionic liquids paired with either the chloride (Cl) or bis(trifluoromethane)sulfonimide (TFSI) anion. Different concentrations of lithium bis(trifluoromethane)sulfonimide (LiTFSI) are subsequently added to the phosphonium ionic liquids to give electrolytes. Based on the performance of the phosphonium TFSI electrolytes with added LiTFSI compared to the chloride analogs, a coin cell is constructed with either the mono- or di-phosphonium TFSI electrolytes along with a Li metal anode and LiCoO2 cathode. Finally, battery performance is evaluated at 100 &#176;C for the two different coin cell batteries. The detailed procedures, the challenges in execution, and the insights gained from performing these experiments are described below.

<table border="0" cellpadding="0" cellspacing="0" width="653">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Silicone oil</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td style="width:119px;">85409</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Potassium hydroxide</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">221473</td>
			<td>Corrosive</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Rotary evaporator</td>
			<td style="width:108px;">Buchi</td>
			<td style="width:119px;">R-124</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">High-vacuum pump</td>
			<td style="width:108px;">Welch</td>
			<td align="right" style="width:119px;">8907</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Nitrogen, ultra high purity</td>
			<td style="width:108px;">Airgas</td>
			<td style="width:119px;">NI UHP300</td>
			<td>Compressed gas</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Tetrahydrofuran, stabilized with BHT</td>
			<td style="width:108px;">Pharmaco-Aaper</td>
			<td align="right" style="width:119px;">346000</td>
			<td>Flammable. Dried through column of XXX</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Dichloromethane</td>
			<td style="width:108px;">Pharmaco-Aaper</td>
			<td align="right" style="width:119px;">313000</td>
			<td>Flammable, toxic.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Separatory funnel (1 L)</td>
			<td style="width:108px;">Fisher Scientific</td>
			<td style="width:119px;">13-678-606</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Sodium sulfate</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">239313</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Ethanol, absolute</td>
			<td style="width:108px;">Pharmaco-Aaper</td>
			<td style="width:119px;">111USP200</td>
			<td>Flammable, toxic.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Buchner funnel</td>
			<td style="width:108px;">Fisher Scientific</td>
			<td style="width:119px;">FB-966-F</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Methanol</td>
			<td style="width:108px;">Pharmaco-Aaper</td>
			<td style="width:119px;">339000ACS</td>
			<td>Flammable, toxic.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Triethylamine (anhydrous)</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">471283</td>
			<td>Toxic, flammable, harmful to environment</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Glass syringe</td>
			<td style="width:108px;">Hamilton Company</td>
			<td style="width:119px;">1700-series</td>
			<td></td>
		</tr>
		<tr height="84">
			<td height="84" style="height:84px;width:259px;">Deuterated chloroform</td>
			<td style="width:108px;">Cambridge Isotopes Laboratories, Inc.</td>
			<td style="width:119px;">DLM-29-10</td>
			<td>Toxic</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Nuclear magnetic resonance instrument</td>
			<td style="width:108px;">Varian</td>
			<td style="width:119px;">V400</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Hydrogen</td>
			<td style="width:108px;">Airgas</td>
			<td style="width:119px;">HY HP300</td>
			<td>Highly flammable.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Hexanes</td>
			<td style="width:108px;">Pharmaco-Aaper</td>
			<td style="width:119px;">359000ACS</td>
			<td>Toxic, flammable.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Differential scanning calorimeter</td>
			<td style="width:108px;">TA Instruments</td>
			<td style="width:119px;">Q100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">N,N-dimethylformamide</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td align="right" style="width:119px;">227056</td>
			<td>Toxic, flammable.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Trihexylphosphone</td>
			<td style="width:108px;">TCI America</td>
			<td style="width:119px;"></td>
			<td>Toxic, flammable.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">1-Chlorodecane</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td style="width:119px;"></td>
			<td>Toxic, flammable.</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Bis(trifluoromethane)sulfonimide lithium salt</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td style="width:119px;"></td>
			<td>Hydrophilic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">1, 10-dichlorodecane</td>
			<td style="width:108px;">Sigma-Aldrich</td>
			<td style="width:119px;"></td>
			<td>Toxic, flammable.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Thermal Gravemetric Analysis (TGA)</td>
			<td style="width:108px;">TA Q50</td>
			<td style="width:119px;">TA instruments</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Differential scanning calorimeter (DSC)</td>
			<td style="width:108px;">TA Q100</td>
			<td style="width:119px;">TA instruments</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Controlled Strain Rheometer</td>
			<td style="width:108px;">AR 1000&#160;</td>
			<td style="width:119px;"></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Conductivity Meter&#160;</td>
			<td style="width:108px;">Consort</td>
			<td style="width:119px;">K912</td>
			<td>4-electrode cell</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;">Potentiostate/Galvanostat</td>
			<td style="width:108px;">Princeton Applied Research&#160;</td>
			<td style="width:119px;">VersaStat MC4&#160;</td>
			<td style="width:167px;">Electrochemical testing</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Separators&#160;</td>
			<td style="width:108px;">Celgard&#160;</td>
			<td style="width:119px;">C480&#160;</td>
			<td style="width:167px;">polypropylene/polyethylene</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">CR2032 coin cells</td>
			<td style="width:108px;">MTI Corp.</td>
			<td style="width:119px;">EQ-CR2032-CASE</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="25">
			<td height="25" style="height:25px;">LiCoO2 electrode&#160;</td>
			<td style="width:108px;">MTI Corp.</td>
			<td style="width:119px;">EQ-CR2032</td>
			<td style="width:167px;">Cathode material</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">lithium metal&#160;</td>
			<td style="width:108px;">Alfa Aesar</td>
			<td align="right" style="width:119px;">10769</td>
			<td style="width:167px;">Anode Material</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Stainless Steel Spacer</td>
			<td style="width:108px;">MTI Corp.</td>
			<td style="width:119px;">EQ-CR20-Spacer304-02</td>
			<td style="width:167px;">15.5 mm Dia x 0.2 mm</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Wave Spring</td>
			<td style="width:108px;">MTI Corp.</td>
			<td style="width:119px;">EQ-CR20WS-Spring304</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:259px;">Electric Coin Cell Crimping Machine</td>
			<td style="width:108px;">MTI Corp.</td>
			<td style="width:119px;">MSK-160D</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:259px;">Glove box</td>
			<td style="width:108px;">Mbraun</td>
			<td style="width:119px;"></td>
			<td style="width:167px;">Water free, oxygen free operation</td>
		</tr>
	</tbody>
</table>

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.

The ionic liquids, mono-HexC10Cl and di-HexC10Cl, were prepared via a nucleophilic reaction, and a subsequent halide exchange reaction gave the mono-HexC10TFSI and di-HexC10TFSI ionic liquids, respectively (Figure 1A).14 All four ionic liquids were colorless and slightly viscous liquids (Figure 1B). A representative 1H NMR of the mono-HexC10TFSI ionic liquid is shown in Figure 1C, and along with mass spectrometry and...

Watch this Scientific Journal Video about Synthesis of Ionic Liquid Based Electrolytes, Assembly of Li-ion Batteries, and Measurements of Performance at High Temperature at JoVE.com

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

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 ...

synthesis-ionic-liquid-based-electrolytes-assembly-li-ion-batteries

Research

JoVE Journal

Engineering

12.9K Views.  Boston University. 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.

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

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 ...

Synthesis and Microdiffraction at Extreme Pressures and Temperatures

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary interiors, design materials with novel properties, understand the mechanical behavior of materials exposed to very high stresses as in explosions or impacts. Synthesis and structural analysis of materials at extreme conditions of pressure and temperature entails remarkable technical challenges. In the laser heated diamond anvil cell (LH-DAC), very high pressure is generated between the tips of two opposing diamond anvils forced against each other; focused infrared laser beams, shined through the diamonds, allow to reach very high temperatures on samples absorbing the laser radiation. When the LH-DAC is installed in a synchrotron beamline that provides extremely brilliant x-ray radiation, the structure of materials under extreme conditions can be probed in situ. LH-DAC samples, although very small, can show highly variable grain size, phase and chemical composition. In order to obtain the high resolution structural analysis and the most comprehensive characterization of a sample, we collect diffraction data in 2D grids and combine powder, single crystal and multigrain diffraction techniques. Representative results obtained in the synthesis of a new iron oxide, Fe4O5 1 will be shown.

The laser heated diamond anvil cell combined with synchrotron micro-diffraction techniques allows researchers to explore the nature and properties of new phases of matter at extreme pressure and temperature (PT) conditions. Heterogeneous samples can be characterized in situ under high pressure by 2D mapping and combined powder, single-crystal and multigrain diffraction approaches.

High pressure compounds and polymorphs are investigated for a broad range of purposes such as determine structures and processes of deep planetary ...

Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75&#176;. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm2, respectively, has decreased the CA to near 15&#176;, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer&#8217;s surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of&#160;the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm2 and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103&#176;. The XPS results indicate ArF laser induced formation of Si&#8211;(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with&#160;H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

Research and Development of High-performance Explosives

Developmental testing of high explosives for military applications involves small-scale formulation, safety testing, and finally detonation performance tests to verify theoretical calculations. For newly developed formulations, the process begins with small-scale mixes, thermal testing, and impact and friction sensitivity. Only then do subsequent larger scale formulations proceed to detonation testing, which will be covered in this paper. Recent advances in characterization techniques have led to unparalleled precision in the characterization of early-time evolution of detonations. The new technique of Photonic Doppler Velocimetry (PDV) for the measurement of detonation pressure will be shared and compared with traditional fiber-optic detonation velocity and plate-dent calculation of detonation pressure. In particular, the role of aluminum in explosive formulations will be discussed. Recent developments led to the development of explosive formulations that result in reaction of aluminum very early in the detonation product expansion. This enhanced reaction leads to changes in the detonation velocity and pressure due to reaction of the aluminum with oxygen in the expanding gas products.

Developmental testing of high explosives for military applications involves small-scale formulation, safety testing, and finally detonation performance tests to verify theoretical calculations. This paper will share typical development tests associated with the measurement of detonation velocity and detonation pressure.

Developmental testing of high explosives for military applications involves small-scale formulation, safety testing, and finally detonation performance ...

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 ...

Probing C84-embedded Si Substrate Using Scanning Probe Microscopy and Molecular Dynamics

This paper reports an array-designed C84-embedded Si substrate fabricated using a controlled self-assembly method in an ultra-high vacuum chamber. The characteristics of the C84-embedded Si surface, such as atomic resolution topography, local electronic density of states, band gap energy, field emission properties, nanomechanical stiffness, and surface magnetism, were examined using a variety of surface analysis techniques under ultra, high vacuum (UHV) conditions as well as in an atmospheric system. Experimental results demonstrate the high uniformity of the C84-embedded Si surface fabricated using a controlled self-assembly nanotechnology mechanism, represents an important development in the application of field emission display (FED), optoelectronic device fabrication, MEMS cutting tools, and in efforts to find a suitable replacement for carbide semiconductors. Molecular dynamics (MD) method with semi-empirical potential can be used to study the nanoindentation of C84-embedded Si substrate. A detailed description for performing MD simulation is presented here. Details for a comprehensive study on mechanical analysis of MD simulation such as indentation force, Young&#39;s modulus, surface stiffness, atomic stress, and atomic strain are included. The atomic stress and von-Mises strain distributions of the indentation model can be calculated to monitor deformation mechanism with time evaluation in atomistic level.

Probing C84-embedded Si Substrate Using Scanning Probe Microscopy and Molecular Dynamics

This paper reports the nanomaterial fabrication of a fullerene Si substrate inspected and verified by nanomeasurements and molecular dynamic simulation.

This paper reports an array-designed C84-embedded Si substrate fabricated using a controlled self-assembly method in an ultra-high vacuum chamber. The ...

A High Performance Impedance-based Platform for Evaporation Rate Detection

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was employed here for demonstration purposes. Multiple evaporation tests on the model compound as a humectant with various concentrations in solutions were conducted for comparison purposes. A conventional weight loss approach is known as the most straightforward, but time-consuming, measurement technique for evaporation rate detection. Yet, a clear disadvantage is that a large volume of sample is required and multiple sample tests cannot be conducted at the same time. For the first time in literature, an electrical impedance sensing chip is successfully applied to a real-time evaporation investigation in a time sharing, continuous and automatic manner. Moreover, as little as 0.5 ml of test samples is required in this impedance-based apparatus, and a large impedance variation is demonstrated among various dilute solutions. The proposed high-sensitivity and fast-response impedance sensing system is found to outperform a conventional weight loss approach in terms of evaporation rate detection.

This paper presents an impedance-based apparatus for evaporation rate detection of solutions. It offers clear advantages over a conventional weight loss approach: a fast response, high-sensitivity detection, a small sample requirement, multiple sample measurements, and easy disassembly for cleaning and reuse purposes.

This paper describes the method of a novel impedance-based platform for the detection of the evaporation rate. The model compound hyaluronic acid was ...

Detecting the Water-soluble Chloride Distribution of Cement Paste in a High-precision Way

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a high-precision chloride profile. Firstly, paste specimens are molded, cured, and exposed to cyclic wet-dry conditions. Then, powder samples at different specimen depths are grinded when the exposure age is reached. Finally, the water-soluble chloride content is detected using a silver nitrate titration method, and chloride profiles are plotted. The key to improving the accuracy of the chloride distribution along the depth is to exclude the error in the powderization, which is the most critical step for testing the distribution of chloride. Based on the above concept, the grinding method in this protocol can be used to grind powder samples automatically layer by layer from the surface inward, and it should be noted that a very thin grinding thickness (less than 0.5 mm) with a minimum error less than 0.04 mm can be obtained. The chloride profile obtained by this method better reflects the chloride distribution in specimens, which helps researchers to capture the distribution features that are often overlooked. Furthermore, this method can be applied to studies in the field of cement-based materials, which require high chloride distribution accuracy.

A protocol for obtaining a water-soluble chloride profile by using a high precision milling method is presented.

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a ...

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone (ITZ)

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect of aggregate surface morphology on the formation of ITZ. First, a model concrete sample is prepared with a spherical ceramic particle in roughly the central part of the cement matrix, acting as a coarse aggregate used in common concrete/mortar. After curing until the designed age, the sample is scanned by X-ray computed tomography to determine the relative location of the ceramic particle inside the cement matrix. Three locations of the ITZ are chosen: above the aggregate, on the side of the aggregate, and below the aggregate. After a series of treatments, the samples are scanned with a SEM-BSE detector. The resultant images were further processed using a digital image processing method (DIP) to obtain quantitative characteristics of the ITZ. The surface morphology is characterized at the pixel level based on the digital image. Thereafter, K-means clustering method is used to illustrate the effect of surface roughness on ITZ formation.

Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ

Hereby, we proposed a protocol to illustrate the effect of aggregate surface morphology on the ITZ microstructure. The SEM-BSE image were quantitatively analyzed to obtain ITZ's porosity gradient via digital image processing and a K-means clustering algorithm was further employed to establish a relationship between porosity gradient and surface roughness.

Here, we present a comprehensive method to illustrate the uneven distribution of the interfacial transition zone (ITZ) around the aggregate and the effect ...

Fabrication and Design of Wood-Based High-Performance Composites

Delignified densified wood is a new promising and sustainable material that possesses the potential to replace synthetic materials, such as glass fiber reinforced composites, due to its excellent mechanical properties. Delignified wood, however, is rather fragile in a wet state, which makes handling and shaping challenging. Here we present two fabrication processes, closed-mold densification and vacuum densification, to produce high-performance cellulose composites based on delignified wood, including an assessment of their advantages and limitations. Further, we suggest strategies for how the composites can be re-used or decomposed at the end-of-life cycle. Closed-mold densification has the advantage that no elaborate lab equipment is needed. Simple screw clamps or a press can be used for densification. We recommend this method for small parts with simple geometries and large radii of curvature. Vacuum densification in an open-mold process is suitable for larger objects and complex geometries, including small radii of curvature. Compared to the closed-mold process, the open-mold vacuum approach only needs the manufacture of a single mold cavity.

Delignified densified wood represents a new promising lightweight, high-performance and bio-based material with great potential to partially substitute natural fiber reinforced- or glass fiber reinforced composites in the future. We here present two versatile fabrication routes and demonstrate the possibility to create complex composite parts.

Delignified densified wood is a new promising and sustainable material that possesses the potential to replace synthetic materials, such as glass fiber ...