The authors would like to thank Weatherford International for providing financial support.

1. Graft Copolymer Synthesis18-19
<ol>
 <li>Synthesize the graft copolymers (POEM-g-PDMS and POEA-g-PDMS at 70:30 weight ratio) using a free radical polymerization approach by mixing 26 ml of POEM (or POEA) monomers (Figure 3), 12 ml of PDMS macromonomers, and 12 mg of 2,2'-Azobis(2-methylpropionitrile) (AIBN) (monomer:initiator [825:1]) in 160 ml of EA.</li>
 <li>Seal the flask containing the clear solution with a rubber septum and purge with ultra high purity argon for 45 min.</li>
 <li>Heat the solution to 72 &deg;C (AIBN has a decomposition rate of 3.2 x 10-5 sec-1) in an oil bath under constant stirring for 24 hr.</li>
 <li>The initially clear solution typically became visibly milky within 2 hr. Precipitate the final solution in an immiscible solvent, PE. Dry the polymer at 80 &deg;C under less than 5 mTorr vacuum for 5 days to remove the residual moisture.</li>
 <li>It was found that if the polymer were not dried properly, the excessive moisture would lead to crack formation when the polymer was casted into thin films.</li>
 <li>The final graft copolymer (shown in Figure 4) had a molecular weight of 500,000 g/mol using gel permeation chromatography with polystyrene calibration standard.</li>
 <li>Complex the graft copolymer with LiTFSI at a Li:EO ratio of 1:20 (1 g of POEM-g-PDMS (70:30) with 170 mg of LiTFSI) in a common solvent of THF to form the electrolyte.</li>
</ol>
2. Preparation of Composite Cathode
<ol>
 <li>Synthesize the cathode by mixing ball-milled LiFePO4 powders (Linyi Gelon New Battery Materials) and carbon black (Super P), and dissolving the mixture in GCE solution at a weight ratio of 5:1:1.</li>
 <li>Heat the slurry to 80 &deg;C (open-cap) while being stirred. Next sonicate the slurry by magnetically stirring to ensure proper mixing. Doctor-blade onto aluminum foil at a loading factor of 10 mg/cm2 onto the aluminum foil to ensure better lamination to the aluminum.</li>
 <li>Dry the composite cathode in a vacuum oven at 80 &deg;C O/N to remove the residual THF and moisture.</li>
</ol>
3. Coin Cell Preparation and Testing
<ol>
 <li>Transport the composite cathode into an argon-filled glovebox, and punch into small discs (area = 1.4 cm2) using a high-precision electrode cutter EL-CUT (EL-CELL). Drop cast pure GCE solution (POEM-g-PDMS, LiTFSI, both dissolved in THF) onto the electrode discs to form the electrolyte layer.</li>
 <li>Heat the final cathode-electrolyte discs on a hot plate inside the glovebox with a dew point of -80 &deg;C to evaporate the THF, and assemble into CR2032 coin cells along with equal-sized GCE-coated metallic lithium discs (Sigma-Aldrich, 0.75 mm thick) using a manual closing tool (Hohsen). The cell schematic is shown in Figure 5, where the gray particles represent LiFePO4, the black particles represent carbon, the blue "spaghetti" represents the GCE, and the anode is lithium metal.</li>
 <li>Assemble a second set of cells comprised of the same LiFePO4 powders and lithium metal anode, but instead use PVDF binder resin (Kynar), PVDF separator (Celgard), and liquid electrolyte of 1 M LiPF6 in EC:DMC at 1:1 ratio (LP30, Merck), to compare the performance.</li>
 <li>All assembly was done in a glovebox with a dew point of -80 &deg;C. A 32-channel MACCOR 4000 battery tester was used for the cycling tests at ambient temperature.</li>
</ol>
4. Polymer Conduction Mechanism
<ol>
 <li>The PEO segmental motions are typically associated with the torsion around C-C and C-O bonds. The semi-random segmental motion assists ion conduction by forming and breaking coordination sites for the solvated ions and providing free volume for the ions to diffuse under the influence of the electric field. The onset of the segmental motion occurs in the vicinity of the glass transition temperature, Tg, and becomes more facile as the temperature increases further beyond the Tg. At higher temperatures, local voids are produced by the polymer expansion, allowing polymer segments to move into the free volume 19.</li>
 <li>Since the segmental motion is far more rapid in the amorphous phase above the Tg than in the crystalline phase, ion transport in polymer occurs predominantly in the amorphous phase. However, recently Li+ conduction in crystalline (PEO)6:LiAsF6 was demonstrated, although the conductivity is more than two orders of magnitude lower than in amorphous PEO. The crystalline or amorphous phase of the PEO/salt complex depends on the composition, temperature, and preparation method 20-22.</li>
 <li>Unlike in liquid, where ions move with their solvent sheath intact and transport is related to the macroscopic viscosity of the solvent; in solid polymer, where the polymer chains are increasingly entangled and cannot move over long distances, the ion transport is related to the microscopic viscosity of the segments of the polymer chains. The transport of ions along polymer chains needs to overcome two activation barriers, both are shown in Figures 6 and 7. One is the solvation of the ions by the coordinating EO units. This process involves the forming and breaking of chemical bonds, has Arrhenius dependence, and the conductivity is given by 
 &sigma;A(Ea/kT) 
 where &sigma; is the conductivity, A is a constant, and Ea is the activation energy associated with the bonds. Because ions must dissociate from the coordination sites in order to move in the solid polymer, if the bonds are too strong, the cations become immobile. The cation-polymer bonds need to be strong enough for salt dissolution, but weak enough to allow for cation mobility.</li>
 <li>The transport of ions is from one coordination site to another. This process is related to the segmental motion of the polymer, has Vogel-Tammann-Fulcher (VTF) dependence 22-25, and the conductivity is where T0 is a reference temperature generally chosen to be 50 K below Tg. This equation suggests that thermal motion above T0 contributes to transport process, and faster motion is expected for polymer with low Tg. The VTF process is related to the Tg, thus rate-limiting at low temperatures. At high temperatures, the segmental motion becomes facile enough that the Arrhenius process becomes rate limiting.</li>
</ol>

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No conflicts of interest declared.

The LiFePO4/GCE/Li curves show greater overpotential than the LiFePO4/LP30/Li curves on both charge and discharge. Since the GCE is used as both electrolyte and binder, ion conduction is provided to all of the cathode particles, and nearly the entire practical specific capacity (150 mAh/g) was accessible. The theoretical specific capacity of 170 mAh/g is not achieved since it is limited by lithium diffusion within LiFePO4 particles, which is low at room temperatures. The cycling capacities for the first 50 deep cycles are shown in the right plot. The energy efficiencies during the first 5 cycles are low (large charge/discharge capacity ratio), possibly due to the reversible capacity loss related to the formation of a passivation layer on lithium anode. The passivation film could result from reactions between lithium metal and residual THF solvent of the CF3SO3- anions, which are known to produce LiF species.
At both 60 &deg;C and 120 &deg;C, the cell exhibits low overpotential due to fast polymer electrolyte conductivity, and nearly the full theoretical specific capacity can be accessed. Full rate capability test of the solid polymer cells were also performed at these three temperatures. At each temperature, the cells were charged at a constant current of 0.05 C (or 25 W/kg considering the cathode loading mass density) and discharged at higher currents. Fresh cells were used for each discharge current to isolate the effect of capacity fade. The rate capability test of a cell with commercial liquid electrolyte (LP30) was also performed at room temperature. The energy densities (integrating the discharge voltage with respect to specific capacity) at different power densities (multiplying the constant current with discharge voltage) are shown in the Ragone plot in Figure 11 for the different temperatures. Figure 11 reflects the tradeoff between energy density and power density. At large currents, the cell performance becomes diffusion limited and the cell capacity decreases. For the LP30-based cells, only room-temperature data were collected. In the case of the GCE-based cells, performance near 60 &deg;C is of particular interest since this temperature is in the range of the melting point of PEO. As indicated in Figure 11 at room temperature the energy densities of the GCE and LP30-based cells are comparable at low power densities. As the power density is increased from 25 to 50 W/kg, the energy density of the GCE-based cells falls drastically. However, at elevated temperatures (&gt;60 &deg;C),the decrease in energy density of the GCE-based cells with increasing power density is significantly smaller due to the higher mobility of PEO chains. Above 60 &deg;C, the performance of the GCE-based cell becomes less dependent on temperature and comparable to the room-temperature performance of the liquid electrolyte-based cells.

Lithium (Li) is a highly electropositive metal (-3.04 V relative to standard hydrogen electrode), and the lightest metal (equivalent weight of 6.94 g/mol and specific gravity of 0.53 g/cm3). This makes it attractive as a choice for the active material in the negative electrode and ideal for portable energy storage devices where size and weight matter. Figure 1 shows that lithium-based batteries (Li ion, PLiON, and Li metal) have higher energy densities than lead-acid, nickel-cadmium, and nickel-metal-hydride batteries 1.
A full lithium-ion battery consists of a cathode (positive), an anode (negative), an electrolyte, and a separator (Figure 2). Both the cathode and the anode are intercalation compounds, where Li-ions can intercalate or de-intercalate reversibly (if the anode is carbon, Li intercalates as neutral Li). The electrolyte provides ionic conduction and insulates electronic conduction between the electrodes. The separator is permeable to ions, but mechanically rigid to keep the two electrodes from shorting. When the cell is in a fully charged state all of the Li has intercalated in the anode, and when the cell is in a fully discharged state all of the Li-ions are intercalated in the cathode. During the spontaneous reaction, discharging electrons flow from the anode to the cathode through an external circuit to power a device, while the ions flow from the anode to the cathode through the electrolyte. The ions and electrons recombine at the cathode to maintain charge neutrality. Upon charging, the flow is reversed.
Most Li-ion battery development to date has focused on cathode materials because they determine the energy density of the battery rather than on the electrolyte, which has remained mostly the same for decades. The electrolyte is a key piece of the battery since it affects the overall power capability due to impedance both through the electrolyte itself and at the electrode-electrolyte interfaces.
The electrolyte used in Li-ion batteries generally consists of a salt of the type LiX and a non-aqueous solvent. Compared to the aqueous electrolytes used in other electrochemical systems, the disadvantages of Li-ion electrolytes are lower conductivity, higher cost, flammability, and environmental problems. Advantages include a wide temperature range (over which the electrolyte remains a liquid) from -150 &deg;C to 300 &deg;C, a wide voltage window (up to 5 V versus Li/Li+), and better compatibility with electrodes (aqueous electrolyte would react violently with Li metal and form LiOH and hydrogen) 2, 3, 4-6.
The main non-aqueous electrolytes used in batteries include organic carbonate-based liquids, polymers, ionic liquids, and ceramics. These electrolytes need to meet certain benchmarks to be used in practical Li-ion batteries. They include a conductivity of at least 10 mS/cm, a large electrochemical window (&gt;4.5 V for high voltage cathodes), low vapor pressure, good thermal and chemical stability, low toxicity, and low cost. For certain stringent applications such as the electric vehicles, all of these benchmarks must be met over a wide temperature range, typically from -20 &deg;C to 60 &deg;C. Since the focus of this work is on organic and polymer electrolytes, the remainder of this paper will focus on these electrolytes.
Carbonate based electrolytes consist of a lithium salt dissolved in an organic solvent. However, it is difficult for any one solvent to meet all of the requirements. For example, solvents with low vapor pressure, such as ethylene carbonate (EC) and propylene carbonate (PC), tend to have higher viscosities, leading to lower conductivity. Also EC is a solid at room temperature; this requires it to be combined with another solvent. Generally the electrolyte is a combination of several solvents. The common solvents and some of their physical properties are listed in Table 1.
<table border="1">
 <tbody>
 <tr>
 <td>Name</td>
 <td>Melting Temperature (&deg;C)</td>
 <td>Boiling Temperature (&deg;C)</td>
 <td>Viscosity (mPa*s)</td>
 </tr>
 <tr>
 <td>Dimethyl Carbonate (DMC)</td>
 <td>4.6</td>
 <td>90</td>
 <td>0.5902 (25 &deg;C)</td>
 </tr>
 <tr>
 <td>Diethyl Carbonate (DEC)</td>
 <td>-43</td>
 <td>126.8</td>
 <td>0.7529 (25 &deg;C)</td>
 </tr>
 <tr>
 <td>Ethylene carbonate (EC)</td>
 <td>36.5</td>
 <td>238</td>
 <td>1.9 (40 &deg;C)</td>
 </tr>
 <tr>
 <td>Propylene Carbonate (PC)</td>
 <td>-54.53</td>
 <td>242</td>
 <td>2.512 (25 &deg;C)</td>
 </tr>
 </tbody>
</table>
Table 1. Common Carbonate Solvents 7.
Safer alternates to organic electrolytes are polymer based electrolytes. Polymer electrolytes are thin-films, non-volatile, non-flammable, and their flexibility allows them to be rolled and printed on a large commercial scale. Wright, et al. first demonstrated ion conduction in poly(ethylene oxide)-salt complexes (PEO) in 1973. It was later discovered that the safety concern associated with dendrite growth on Li metal in liquid electrolyte could be resolved by using PEO-based solid polymer electrolyte, which suppressed the growth of dendrites 8-17. There are three main types of polymer electrolytes: (1) solvent free dry solid polymer, (2) gel electrolytes, and (3) plasticized polymer, with a solvent free dry synthesis used in our work.
This paper will discuss (a) the solvent free dry polymer synthesis, (b) the polymer conduction mechanism, and (c) provide temperature cycling for both solid polymer and organic electrolytes.

<table border="1">
	<tbody>
		<tr>
			<td>Name of the reagent</td>
			<td>Company</td>
			<td>Catalogue number</td>
			<td>Comments (optional)</td>
		</tr>
		<tr>
			<td>POEM</td>
			<td>Sigma Aldrich</td>
			<td>26915-72-0</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>POEA</td>
			<td>Sigma Aldrich</td>
			<td>32171-39-4</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>LiTFSI</td>
			<td>Sigma Aldrich</td>
			<td>90076-65-6</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>AIBN</td>
			<td>Sigma Aldrich</td>
			<td>78-67-1</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>EA</td>
			<td>Sigma Aldrich</td>
			<td>141-78-6</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>THF</td>
			<td>Sigma Aldrich</td>
			<td>109-99-9</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>PDMS</td>
			<td>Gelest</td>
			<td>146632-07-7</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Argon Gas</td>
			<td>Air Gas</td>
			<td>&nbsp;</td>
			<td>Ultra high purity (Grade 5)</td>
		</tr>
		<tr>
			<td>PE</td>
			<td>Sigma Aldrich</td>
			<td>8032-32-4</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>LiFePO4</td>
			<td>Gelon</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Carbon black</td>
			<td>SuperP</td>
			<td>&nbsp;</td>
			<td>Super P</td>
		</tr>
		<tr>
			<td>Lithium metal</td>
			<td>Alfa Aesar</td>
			<td>7439-93-2</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>PVDF binder resin</td>
			<td>Kynar</td>
			<td>&nbsp;</td>
			<td>Kynar</td>
		</tr>
		<tr>
			<td>PVDF Separator</td>
			<td>Celgard</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>LP30</td>
			<td>Merck</td>
			<td>&nbsp;</td>
			<td>LiPF6 in EC:DMC</td>
		</tr>
		<tr>
			<td>MACCOR battery tester</td>
			<td>MACCOR</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>El-Cut</td>
			<td>EL-CELL</td>
			<td>&nbsp;</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

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.

The room temperature cell cycling performance is shown in Figure 8. The left plot shows the charge and discharge profiles of cells with conventional liquid electrolyte (LP30) at 15 mA/g, and GCE/binder at 10 mA/g. Figure 9 shows the discharge voltage profiles of the solid polymer cells at room temperature, 60 &#176;C, and 120 &#176;C using a low current of 0.05 C. The discharge voltage profiles as functions of specific capacity are shown in Figure 10,where the discharge current is in &#956;A and labeled next to the discharge curve. Figure 10 shows poor rate capability at room temperature and much better rate capability at elevated temperatures. The energy densities (integrating the discharge voltage with respect to specific capacity) at different power densities (multiplying the constant current with discharge voltage) are shown in the Ragone plot in Figure 11 for the different temperatures.
<img alt="Figure 1" src="/files/ftp_upload/50067/50067fig1.jpg" /> 
Figure 1. Energy densities for various batteries 1.
<img alt="Figure 2" src="/files/ftp_upload/50067/50067fig2.jpg" /> 
Figure 2. A full lithium-ion cell during discharging.
<img alt="Figure 3" src="/files/ftp_upload/50067/50067fig3.jpg" /> 
Figure 3. POEM and PDMS.
<img alt="Figure 4" src="/files/ftp_upload/50067/50067fig4.jpg" /> 
Figure 4. The Synthesized Graft Copolymer.
<img alt="Figure 5" src="/files/ftp_upload/50067/50067fig5.jpg" /> 
Figure 5. Schematic of a solid polymerlithium battery.
<img alt="Figure 6" src="/files/ftp_upload/50067/50067fig6.jpg" /> 
Figure 6. Contributions to ion mobility 18.
<img alt="Figure 7" src="/files/ftp_upload/50067/50067fig7.jpg" /> 
Figure 7. Conductivity of POEM and POEA at different temperatures.
<img alt="Figure 8" src="/files/ftp_upload/50067/50067fig8.jpg" /> 
Figure 8. Room Temperature Cycling 26.
<img alt="Figure 9" src="/files/ftp_upload/50067/50067fig9.jpg" /> 
Figure 9. Discharge voltage profiles at different temperatures. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/50067/50067fig9large.jpg" target="_blank"> Click here to view larger figure</a>.
<img alt="Figure 10" src="/files/ftp_upload/50067/50067fig10.jpg" /> 
Figure 10. Discharge rate capability at different temperatures. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/50067/50067fig10large.jpg" target="_blank"> Click here to view larger figure</a>.
<img alt="Figure 11" src="/files/ftp_upload/50067/50067fig11.jpg" /> 
Figure 11. Ragone plot for polymer and liquid electrolyte batteries at different temperature 26.
Table 1. Common Carbonate Solvents.
List of Acronyms
2,2&#39;-Azobis(2-methylpropionitrile) (AIBN) 
Graft copolymer electrolyte (GCE) 
Diethyl carbonate (DEC) 
Dimethyl carbonate (DMC) 
Ethylene oxide (EO) 
Ethylene carbonate (EC) 
Ethyl acetate (EA) 
Glass transition temperature (Tg) 
Lithium hexafluorophosphate (LiPF6) 
LP30 (LiPF6 in EC:DMC at a 1:1 ratio) 
Lithium iron phosphate (LiFePO4)
Lithium Hexafluoroarsenate (LiAsF6)
Lithium bis(trifluoromethane)sulfonamide (LiTFSI) 
Petroleum ether (PE) 
Polydimethylsiloxane (PDMS) 
Poly(oxyethylene) methacrylate (POEM) 
Poly(oxyethylene) acrylate (POEA) 
Propylene carbonate (PC) 
Polyvinyl difluoride (PVDF) 
Tetrahydrofuran (THF) 
Vogel-Tammann-Fulcher (VTF)

Watch this Scientific Journal Video about Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications at JoVE.com

Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications

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 ...

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21.5K Views.  Massachusetts Institute of Technology. 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 (>120 °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 m...

Video: Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications

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 ...

Hyperpolarized Xenon for NMR and MRI Applications

Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) suffer from intrinsic low sensitivity because even strong external magnetic fields of ~10 T generate only a small detectable net-magnetization of the sample at room temperature 1. Hence, most NMR and MRI applications rely on the detection of molecules at relative high concentration (e.g., water for imaging of biological tissue) or require excessive acquisition times. This limits our ability to exploit the very useful molecular specificity of NMR signals for many biochemical and medical applications. However, novel approaches have emerged in the past few years: Manipulation of the detected spin species prior to detection inside the NMR/MRI magnet can dramatically increase the magnetization and therefore allows detection of molecules at much lower concentration 2.
Here, we present a method for polarization of a xenon gas mixture (2-5% Xe, 10% N2, He balance) in a compact setup with a ca. 16000-fold signal enhancement. Modern line-narrowed diode lasers allow efficient polarization 7 and immediate use of gas mixture even if the noble gas is not separated from the other components. The SEOP apparatus is explained and determination of the achieved spin polarization is demonstrated for performance control of the method.
The hyperpolarized gas can be used for void space imaging, including gas flow imaging or diffusion studies at the interfaces with other materials 8,9. Moreover, the Xe NMR signal is extremely sensitive to its molecular environment 6. This enables the option to use it as an NMR/MRI contrast agent when dissolved in aqueous solution with functionalized molecular hosts that temporarily trap the gas 10,11. Direct detection and high-sensitivity indirect detection of such constructs is demonstrated in both spectroscopic and imaging mode.

The production of hyperpolarized xenon by means of spin exchange optical pumping (SEOP) is described. This method yields a ~10000-fold enhancement of the nuclear spin polarization of Xe-129 and has applications in nuclear magnetic resonance spectroscopy and imaging. Examples of gas phase and solution state experiments are given.

Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) suffer from intrinsic low sensitivity because even strong external magnetic fields of ~10 ...

Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells

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

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

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

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. ...

Fine-tuning the Size and Minimizing the Noise of Solid-state Nanopores

Solid-state nanopores have emerged as a versatile tool for the characterization of single biomolecules such as nucleic acids and proteins1. However, the creation of a nanopore in a thin insulating membrane remains challenging. Fabrication methods involving specialized focused electron beam systems can produce well-defined nanopores, but yield of reliable and low-noise nanopores in commercially available membranes remains low2,3 and size control is nontrivial4,5. Here, the application of high electric fields to fine-tune the size of the nanopore while ensuring optimal low-noise performance is demonstrated. These short pulses of high electric field are used to produce a pristine electrical signal and allow for enlarging of nanopores with subnanometer precision upon prolonged exposure. This method is performed in situ in an aqueous environment using standard laboratory equipment, improving the yield and reproducibility of solid-state nanopore fabrication.

A methodology for preparing solid-state nanopores in solution for biomolecular translocation experiments is presented. By applying short pulses of high electric fields, the nanopore diameter can be controllably enlarged with subnanometer precision and its electrical noise characteristics significantly improved. This procedure is performed in situ using standard laboratory equipment under experimental conditions.

Solid-state nanopores have emerged as a versatile tool for the characterization of single biomolecules such as nucleic acids and proteins1. However, the ...

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 ...

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 ...

All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics

The miniaturization of semiconductor devices to scales where small numbers of dopants can control device properties requires the development of new techniques capable of characterizing their dynamics. Investigating single dopants requires sub-nanometer spatial resolution, which motivates the use of scanning tunneling microscopy (STM). However, conventional STM is limited to millisecond temporal resolution. Several methods have been developed to overcome this shortcoming, including all-electronic time-resolved STM, which is used in this study to examine dopant dynamics in silicon with nanosecond resolution. The methods presented here are widely accessible and allow for local measurement of a wide variety of dynamics at the atomic scale. A novel time-resolved scanning tunneling spectroscopy technique is presented and used to efficiently search for dynamics.

We demonstrate an all-electronic method to observe nanosecond-resolved charge dynamics of dopant atoms in silicon with a scanning tunneling microscope.

The miniaturization of semiconductor devices to scales where small numbers of dopants can control device properties requires the development of new ...

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

A method of carrier number control by electrolyte gating is demonstrated. We have obtained WS2 thin flakes with atomically flat surface via scotch tape method or individual WS2 nanotubes by dispersing the suspension of WS2 nanotubes. The selected samples have been fabricated into devices by the use of the electron beam lithography and electrolyte is put on the devices. We have characterized the electronic properties of the devices under applying the gate voltage. In the small gate voltage region, ions in the electrolyte are accumulated on the surface of the samples which leads to the large electric potential drop and resultant electrostatic carrier doping at the interface. Ambipolar transfer curve has been observed in this electrostatic doping region. When the gate voltage is further increased, we met another drastic increase of source-drain current which implies that ions are intercalated into layers of WS2 and electrochemical carrier doping is realized. In such electrochemical doping region, superconductivity has been observed. The focused technique provides a powerful strategy for achieving the electric-filed-induced quantum phase transition.

Electric-field Control of Electronic States in WS2 Nanodevices by Electrolyte Gating

Here, we present a protocol to control the carrier number in solids by using the electrolyte.

A method of carrier number control by electrolyte gating is demonstrated. We have obtained WS2 thin flakes with atomically flat surface via scotch tape ...

Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser

The goal of this protocol is to present how to perform spin- and angle-resolved photoemission spectroscopy combined with polarization-variable 7-eV laser (laser-SARPES), and demonstrate a power of this technique for studying solid state physics. Laser-SARPES achieves two great capabilities. Firstly, by examining orbital selection rule of linearly polarized lasers, orbital selective excitation can be carried out in SAPRES experiment. Secondly, the technique can show full information of a variation of the spin quantum axis as a function of the light polarization. To demonstrate the power of the collaboration of these capabilities in laser-SARPES, we apply this technique for the investigations of spin-orbit coupled surface states of Bi2Se3. This technique affords to decompose spin and orbital components from the spin-orbit coupled wavefunctions. Moreover, as a representative advantage of using the direct spin detection collaborated with the polarization-variable laser, the technique unambiguously visualizes the light polarization dependence of the spin quantum axis in three-dimension. Laser-SARPES dramatically increases a capability of photoemission technique.

Here, we combine polarization-variable 7-eV laser with spin- and angle-resolved photoemission technique to visualize the spin-orbital coupling effect in solid states.

The goal of this protocol is to present how to perform spin- and angle-resolved photoemission spectroscopy combined with polarization-variable 7-eV laser ...

Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications

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Construction and Testing of Coin Cells of Lithium Ion Batteries

Hyperpolarized Xenon for NMR and MRI Applications

Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells

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

Fine-tuning the Size and Minimizing the Noise of Solid-state Nanopores

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

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

All-electronic Nanosecond-resolved Scanning Tunneling Microscopy: Facilitating the Investigation of Single Dopant Charge Dynamics

Electric-field Control of Electronic States in WS₂ Nanodevices by Electrolyte Gating

Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser