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><tbody><tr><td>Silicone oil</td><td>Sigma-Aldrich</td><td>85409</td><td></td></tr><tr><td>Potassium hydroxide</td><td>Sigma-Aldrich</td><td>221473</td><td>Corrosive</td></tr><tr><td>Rotary evaporator</td><td>Buchi</td><td>R-124</td><td></td></tr><tr><td>High-vacuum pump</td><td>Welch</td><td>8907</td><td></td></tr><tr><td>Nitrogen, ultra high purity</td><td>Airgas</td><td>NI UHP300</td><td>Compressed gas</td></tr><tr><td>Tetrahydrofuran, stabilized with BHT</td><td>Pharmco-Aaper</td><td>346000</td><td>Flammable. Dried before use.</td></tr><tr><td>Dichloromethane</td><td>Pharmco-Aaper</td><td>313000</td><td>Flammable, toxic.</td></tr><tr><td>Separatory funnel (1 L)</td><td>Fisher Scientific</td><td>13-678-606</td><td></td></tr><tr><td>Sodium sulfate</td><td>Sigma-Aldrich</td><td>239313</td><td></td></tr><tr><td>Ethanol, absolute</td><td>Pharmco-Aaper</td><td>111USP200</td><td>Flammable, toxic.</td></tr><tr><td>Buchner funnel</td><td>Fisher Scientific</td><td>FB-966-F</td><td></td></tr><tr><td>Methanol</td><td>Pharmco-Aaper</td><td>339000ACS</td><td>Flammable, toxic.</td></tr><tr><td>Triethylamine (anhydrous)</td><td>Sigma-Aldrich</td><td>471283</td><td>Toxic, flammable, harmful to environment</td></tr><tr><td>Glass syringe</td><td>Hamilton Company</td><td>1700-series</td><td></td></tr><tr><td>Deuterated chloroform</td><td>Cambridge Isotopes Laboratories, Inc.</td><td>DLM-29-10</td><td>Toxic</td></tr><tr><td>Nuclear magnetic resonance instrument</td><td>Varian</td><td>V400</td><td></td></tr><tr><td>Hydrogen</td><td>Airgas</td><td>HY HP300</td><td>Highly flammable.</td></tr><tr><td>Hexanes</td><td>Pharmco-Aaper</td><td>359000ACS</td><td>Toxic, flammable.</td></tr><tr><td>Differential scanning calorimeter</td><td>TA Instruments</td><td>Q100</td><td></td></tr><tr><td>&lt;em&gt;N,N&lt;/em&gt;-dimethylformamide</td><td>Sigma-Aldrich</td><td>227056</td><td>Toxic, flammable.</td></tr><tr><td>Trihexylphosphone</td><td>TCI America</td><td></td><td>Toxic, flammable.</td></tr><tr><td>1-Chlorodecane</td><td>Sigma-Aldrich</td><td></td><td>Toxic, flammable.</td></tr><tr><td>Bis(trifluoromethane)sulfonimide lithium salt</td><td>Sigma-Aldrich</td><td></td><td>Hydrophilic</td></tr><tr><td>1,10-dichlorodecane</td><td>Sigma-Aldrich</td><td></td><td>Toxic, flammable.</td></tr><tr><td>Thermal Gravemetric Analysis (TGA)</td><td>TA Q50</td><td>TA instruments</td><td></td></tr><tr><td>Differential scanning calorimeter (DSC)</td><td>TA Q100</td><td>TA instruments</td><td></td></tr><tr><td>Controlled Strain Rheometer</td><td>AR 1000&amp;nbsp;</td><td></td><td></td></tr><tr><td>Conductivity Meter&amp;nbsp;</td><td>Consort</td><td>K912</td><td>4-electrode cell</td></tr><tr><td>Potentiostat/Galvanostat</td><td>Princeton Applied Research&amp;nbsp;</td><td>VersaStat MC4&amp;nbsp;</td><td>Electrochemical testing</td></tr><tr><td>Separators</td><td>Celgard&amp;nbsp;</td><td>C480&amp;nbsp;</td><td>polypropylene/polyethylene</td></tr><tr><td>CR2032 coin cells</td><td>MTI Corp.</td><td>EQ-CR2032-CASE</td><td></td></tr><tr><td>LiCoO&lt;sub&gt;2&lt;/sub&gt; electrode&amp;nbsp;</td><td>MTI Corp.</td><td>EQ-CR2032</td><td>Cathode material</td></tr><tr><td>lithium metal&amp;nbsp;</td><td>Alfa Aesar</td><td>10769</td><td>Anode Material</td></tr><tr><td>Stainless Steel Spacer</td><td>MTI Corp.</td><td>EQ-CR20-Spacer304-02</td><td>15.5 mm Dia x 0.2 mm</td></tr><tr><td>Wave Spring</td><td>MTI Corp.</td><td>EQ-CR20WS-Spring304</td><td></td></tr><tr><td>Electric Coin Cell Crimping Machine</td><td>MTI Corp.</td><td>MSK-160D</td><td></td></tr><tr><td>Glove box</td><td>Mbraun</td><td></td><td>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

Universidad de Cartagena UDEC

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 ...

Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications

Battery safety has been a very important research area over the past decade. Commercially available lithium ion batteries employ low flash point (&lt;80 &deg;C), flammable, and volatile organic electrolytes. These organic based electrolyte systems are viable at ambient temperatures, but require a cooling system to ensure that temperatures do not exceed 80 &deg;C. These cooling systems tend to increase battery costs and can malfunction which can lead to battery malfunction and explosions, thus endangering human life. Increases in petroleum prices lead to a huge demand for safe, electric hybrid vehicles that are more economically viable to operate as oil prices continue to rise. Existing organic based electrolytes used in lithium ion batteries are not applicable to high temperature automotive applications. A safer alternative to organic electrolytes is solid polymer electrolytes. This work will highlight the synthesis for a graft copolymer electrolyte (GCE) poly(oxyethylene) methacrylate (POEM) to a block with a lower glass transition temperature (Tg) poly(oxyethylene) acrylate (POEA). The conduction mechanism has been discussed and it has been demonstrated the relationship between polymer segmental motion and ionic conductivity indeed has a Vogel-Tammann-Fulcher (VTF) dependence. Batteries containing commercially available LP30 organic (LiPF6 in ethylene carbonate (EC):dimethyl carbonate (DMC) at a 1:1 ratio) and GCE were cycled at ambient temperature. It was found that at ambient temperature, the batteries containing GCE showed a greater overpotential when compared to LP30 electrolyte. However at temperatures greater than 60 &deg;C, the GCE cell exhibited much lower overpotential due to fast polymer electrolyte conductivity and nearly the full theoretical specific capacity of 170 mAh/g was accessed.

Lithium ion batteries employ flammable and volatile organic electrolytes that are suitable for ambient temperature applications. A safer alternative to organic electrolytes are solid polymer batteries. Solid polymer batteries operate safely at high temperatures (&gt;120 &deg;C), thus making them applicable to high temperature applications such as deep oil drilling and hybrid electric vehicles. This paper will discuss (a) the polymer synthesis, (b) the polymer conduction mechanism, and (c) provide temperature cycling for both solid polymer and organic electrolytes.

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

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. ...

Ultrasound Velocity Measurement in a Liquid Metal Electrode

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently more difficult than measuring the flow of a transparent fluid, since optical methods are not applicable. Ultrasound can be used to measure the velocity of an opaque fluid, not only at isolated points, but at hundreds or thousands of points arrayed along lines, with good temporal resolution. When applied to a liquid metal electrode, ultrasound velocimetry involves additional challenges: high temperature, chemical activity, and electrical conductivity. Here we describe the experimental apparatus and methods that overcome these challenges and allow the measurement of flow in a liquid metal electrode, as it conducts current, at operating temperature. Temperature is regulated within &#177;2 &#176;C using a Proportional-Integral-Derivative (PID) controller that powers a custom-built furnace. Chemical activity is managed by choosing vessel materials carefully and enclosing the experimental setup in an argon-filled glovebox. Finally, unintended electrical paths are carefully prevented. An automated system logs control settings and experimental measurements, using hardware trigger signals to synchronize devices. This apparatus and these methods can produce measurements that are impossible with other techniques, and allow optimization and control of electrochemical technologies like liquid metal batteries.

Ultrasound velocimetry is used to study mixing by fluid flow in liquid metal electrodes. The focus of this manuscript is to illustrate the methods used for making precise, spatially-resolved ultrasound measurements while limiting oxidation and controlling and monitoring temperature, applied current, and the heater power being supplied.

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently ...

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 ...

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

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

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

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

Preparation of Graphene Liquid Cells for the Observation of Lithium-ion Battery Material

In this work, we introduce the preparation of graphene liquid cells (GLCs), encapsulating both electrode materials and organic liquid electrolytes between two graphene sheets, and the facile synthesis of one-dimensional nanostructures using electrospinning. The GLC enables in situ transmission electron microscopy (TEM) for the lithiation dynamics of electrode materials. The in situ GLC-TEM using an electron beam for both imaging and lithiation can utilize not only realistic battery electrolytes, but also the high-resolution imaging of various morphological, phase, and interfacial transitions.

Here, we present a protocol for the fabrication and preparation of a graphene liquid cell for in situ transmission electron microscopy observation, along with a synthesis of electrode materials and electrochemical battery cell tests.

In this work, we introduce the preparation of graphene liquid cells (GLCs), encapsulating both electrode materials and organic liquid electrolytes between ...

Identification and Quantification of Decomposition Mechanisms in Lithium-Ion Batteries; Input to Heat Flow Simulation for Modeling Thermal Runaway

The risks and possible accidents related to the normal use of lithium-ion batteries remain a serious concern. In order to get a better understanding of thermal runaway (TR), the exothermic decomposition reactions in anode and cathode were studied, using a Simultaneous Thermal Analysis (STA)/Gas Chromatography-Mass Spectrometry (GC-MS)/Fourier Transform Infrared (FTIR) spectrometer system. These techniques allowed the identification of the reaction mechanisms in each electrode, owing to the analysis of evolved gaseous species, the amount of heat released and mass loss. These results provided insight into the thermal events happening within a broader temperature range than covered in previously published models. This allowed the formulation of an improved thermal model to depict TR. The heat of reaction, activation energy, and frequency factor (thermal triplets) for each major exothermic process at material level were investigated in a Lithium Nickel-Manganese-Cobalt-Oxide (NMC (111))-Graphite battery cell. The results were analyzed, and their kinetics were derived. These data can be used to successfully simulate the experimental heat flow.

This work aims at determining the reaction kinetics of Li-ion battery cathode and anode materials undergoing thermal runaway (TR). Simultaneous Thermal Analysis (STA)/Fourier Transform Infrared (FTIR) spectrometer/Gas Chromatography Mass Spectrometry (GC-MS) were used to reveal thermal events and to detect evolved gases.

The risks and possible accidents related to the normal use of lithium-ion batteries remain a serious concern. In order to get a better understanding of ...

Chemistry

Synthesizing a Gel Polymer Electrolyte for Supercapacitors, Assembling a Supercapacitor Using a Coin Cell, and Measuring Gel Electrolyte Performance

Supercapacitors (SC) have attracted attention as energy storage devices due to their high density and long cycle performance. SCs used in devices operating in stretchable systems require stretchable electrolytes. Gel polymer electrolytes (GPEs) are an ideal replacement for liquid electrolytes. Polyvinyl alcohol (PVA) and polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) have been widely applied as a polymer-matrix-based electrolytes for supercapacitors because of their low cost, chemically stable, wide operating temperature range, and high ionic conductivities. Herein, we describe the procedures for (1) synthesizing a gel polymer electrolyte with PVA and PVDF-HFP, (2) measuring the electrochemical stability of the gel polymer electrolytes by cyclic voltammetry (CV), (3) measuring the ionic conductivity of the gel polymer electrolytes by electrochemical impedance spectroscopy (EIS), (4) assembling symmetric coin cells using activated carbon (AC) electrodes with the PVA- and PVDF-HFP-based gel polymer electrolytes, and (5) evaluating the electrochemical performance using galvanostatic charge-discharge analysis (GCD) and CV at 25 &#176;C. Additionally, we describe the challenges and insights gained from these experiments.

We present a protocol to test the electrochemical and physical properties of a supercapacitor gel polymer electrolyte using a coin cell.