bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Role of Thiourea As an Electrolyte Additive in Lithium-Sulfur Batteries
Authors: Rafie Ayda , Kalra Vibha 
Published: July 2021

Lithium-sulfur batteries offer five times more energy density compared to commercialized Lithium-ion batteries. Theoretical capacity in Li-S batteries reaches to ~1675 mAh/g making them a great candidate for next-generation batteries. Despite the advantages of Li-S batteries, they suffer from poor cycle life. The main challenge in achieving long-term cycling in Li-S batteries, known as polysulfide shuttling, is the dissolution and diffusion of highly soluble intermediate species, lithium polysulfides. Polysulfide shuttling results in a loss of active material and low efficiency of the Li-S battery. Moreover, Li2S, as the final discharge product, is an electronic and ionic insulator; consequently, activation of such material in the charge process of a Li-S battery becomes a challenge.
In the present work, thiourea is used as an additive in the ether-based electrolyte, commonly used in Li-S batteries. We integrated electrochemical characterization and testing with in-situ spectroscopy to understand the potential role of thiourea in enhancing battery cycle life. Specifically, we hypothesized that thiourea facilitates stable cycling via favorable interactions between its C=S and C-NH2 bonds and intermediate lithium polysulfides. To understand the reaction mechanism and to test our hypothesis, we carried out in situ FTIR experiments. Using in situ FTIR results, lithium polysulfide interaction can be studied through monitoring the changes in the vibrational mode of existing bonds. Our electrochemical results show that the Li-S battery with a very low thiourea concentration of 0.02 M, enabled an initial capacity of 800 mAh/g at C/2 rate. The discharge capacity stabilized at 700 mAh/g after 20 cycles and remained stable for up to 200 cycles (figure 1a), unlike the reference battery with no-additive electrolyte that remained stable for only 80 cycles (figure 1a inset). As a result of reduced polysulfide shuttling, the coulombic efficiency of the battery remained >98% throughout the cycling. The electrochemical results show that this additive plays a significant role in enhancing the cycling stability of Li-S batteries. Moreover, we found out that thiourea is electrochemically active in this voltage range. Based on the redox activity of this additive, we believe that thiourea can potentially be used as a redox mediator to activate Li2S in the charging process. To understand the potential effect of thiourea as a redox mediator, we synthesized Li2S/CNF nanofibers. The electrochemical testing of Li2S/CNF nanofibers shows a significant difference when thiourea is added to the conventional ether electrolyte. Based on the electrochemical results obtained, we believe that thiourea has two simultaneous effects on the performance of Li-S batteries. It can perform as an additive to bind Lithium polysulfides and reduce shuttling of these species. Moreover, as a redox mediator, it can activate Li2S in the charging process.

Figure 1
A Critical Investigation of the Viability of Fast Charging of Lithium-Metal Batteries in Glyme-Ether Electrolytes
Authors: Dutta Arghya , Kubo Yoshimi 
Published: July 2021

Widespread adoption of electric vehicles (EVs) largely depends on the development of efficient battery systems having high energy density with the capability of fast charging. In this regard, lithium (Li) metal-based batteries, such as Li-Oxygen and Li-Sulfur batteries, can provide much higher energy density compared to that of Li-ion batteries. However, low rate-capability of both Li-Oxygen and Li-Sulfur cells hinders their practical utilizations. It has been found that transport limitations in the electrolyte play a major role in affecting the rate-capability of the cells. Therefore, identifying a suitable electrolyte with high ionic conductivity is an essential requirement to improve the rate-capability of these batteries. Additionally, a desired electrolyte must also be stable toward the electrode processes in the cell. Glyme-ether based electrolytes, in these instances, are a preferred class of electrolytes for both Li-Oxygen and Li-Sulfur batteries due to their acceptable compatibility with Li metal as well as with the porous carbon electrodes. Nevertheless, the length of the glyme-ethers dramatically affects the ionic conductivities of the electrolytes and decides the rate-capability of the battery. Therefore, in this work we have investigated the viability of fast Li-plating in different glyme-ether electrolytes and critically analyzed the effects of ion-transport and also assessed the relative stabilities of the electrolytes during Li stripping/plating processes.
The present study involves investigation of Li stripping/plating in six different electrolytes using three glyme-ethers, diglyme (G2), triglyme (G3) and tetraglyme (G4), as the electrolyte solvents with lithium nitrate (LiNO3) or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as the Li salts (1 M) and lithium bromide (LiBr) as an additive (0.05 M). It has been found that the ionic conductivity of the electrolyte increases as the glyme becomes smaller or highly associated LiNO3 is replaced with LiTFSI. As a result, both smaller glymes and LiTFSI help to achieve Li-plating at faster rates. However, unfortunately, stability of Li-plating in terms of Coulombic efficiency and overall cycle-life decreases in smaller glymes or in LiTFSI as the Li salt and detailed investigations reveal formation of unstable SEI to be responsible for lower stability of Li-plating in these electrolytes. Our results show that the consequences of increasing the ionic conductivity of the electrolyte by simply changing the glyme-ether solvent in Li-metal batteries are quite complex and warrant careful consideration of their relative stabilities with the electrode. All the results, in depth analyses and future perspectives of this work will be discussed during the presentation.
Testing with Thin Lithium Anode and Practical Capacities for Fast Evaluation of Polymer Electrolytes for Solid-State Batteries
Authors: Sahore Ritu , Du Zhijia , Chen Xi Chelsea , Westover Andrew S , Dudney Nancy 
Published: July 2021

Lithium metal solid-state batteries can reach greater than 400 Wh/kg energy density compared to ~300 Wh/kg of conventional lithium-ion batteries. However, the amount of inactive material needs to be significantly reduced, and active material loading maximized. For example, the lithium metal anode needs to be <10 µm, the solid electrolyte separator layer needs to be <20 µm, and the cathode capacity >4 mAh/cm2. Several new inorganic and polymeric electrolytes have been discovered in the past decade. Nevertheless, the integration and testing of these novel candidate materials into functioning cells with the electrode loadings and dimensions required to meet the cell-level energy density goals have been limited. For example, typically, hundreds of microns thick lithium foils are used, which can hide any lithium losses at the anode due to reactions or physical isolation and lead to artificially long cycle life. The amount of lithium cycled is also typically too low (<1 mAh/cm2) compared to the desired 4 mAh/cm2 in both symmetric and full-cell tests. Such testing makes it difficult to gauge the progress of the field in reaching practical energy density goals. We argue that testing new materials solutions at full-cell level with practical electrode loading/dimensions can help understand their limitations quicker and progress faster towards reaching the cell-level energy density goal of >400 Wh/kg.
In this work, using two polymer electrolytes (a “dry” and a gel-type), we present several examples that demonstrate the impact on solid-state battery performance as electrode thicknesses/loadings and cycling capacities are shifted towards practical values. First, using thermally-evaporated ultra-thin (1-10 µm) lithium metal anodes, we quantified the lithium losses during cycling at the lithium/polymer-electrolyte interface. Our results show severe lithium losses or ultra-low coulombic efficiency of a common gel-polymer electrolyte leading to complete consumption of the lithium reservoir within a few cycles. Second, we present examples that highlight the challenges of increasing cycling capacities towards practical values. These examples underscore the need to test novel materials solutions directly with such practical capacities, either in full-cell or symmetric-cell formats, to accelerate the materials development endeavors.
Polymer Templating Method for the Formation of Hierarchically Porous Nitrogen-Rich Tin-Carbon Composite Anodes
Authors: Weeks Jason Alexander 
Published: July 2021

This study aims to provide a new platform for the fabrication of metal-carbon composites. Herein we show that the high density crosslinking of a polymer can be used to homogenously trap metal nanoparticles and other components. In this setting, we utilized the cross-linking of poly(maleic anhydride-at 1-octadecene) [PMAO] with ethylene glycol to trap metal nanoparticles and carbon nitride (C3N4) within the polymeric structure. During inert, high-temperature pyrolysis, the polymer acts as a soft-template and prevents agglomeration of metallic tin during the synthesis. Inspired by the work of Tang et al. the carbon nitride is employed to act as a nitrogen dopant source and textural template for the final product. Through an analysis variable experimental parameter, we have shown that this method provides an avenue for the tunable fabrication of nitrogen-rich porous composites. To demonstrate the practicality of this synthetic method, composites with a variety of different nitrogen moieties and textural compositions were electrochemically analyzed. The resulting composites were then used as a platform to demonstrate not only the tunability of the synthetic method but also an example of how much these effects drastically dictate the electrochemistry of the system. Of the samples analyzed it was shown that a urea based composite demonstrated the best electrochemistry touting high rate capability, stable cycling, and high coulombic efficiency (CE).
The results of long-term performance testing reveal the excellent electrochemical properties of the U-Sn-CN composite, supplying an initial capacity of ~ 600 mAh g–1 and 82.0 % capacity retention over 400 cycles at a high current density of 1 A g–1 (1C) with an average CE of 99.8 %. Lower current density studies [500 mA g-1 (C/2)] have shown the material to have an initial capacity of ~ 640 mAh g–1 with 86.0 % capacity retention over 400 cycles. Electrochemical and post-mortem analysis of this composite material suggest the performance properties can be attributed to the unique nitrogen-doped carbon framework, which is able to buffer the large volumetric expansion of the tin due to its disordered flexible nature whilst contributing to the overall capacity of the composite from its high degree of nitrogen doping (~11.9 at %).

Figure 1
Development of Si/C6 Negative Electrode for High Capacity Lithium-Sulfur Batteries
Authors: Tsunoda Uran , Ushioda Yusuke , Machida Kazuki , Seki Shiro 
Published: July 2021

Recently, lithium-sulfur batteries are attracting attention as large-capacity energy storage devices for renewable energy. Lithium-sulfur battery uses elemental sulfur (S8) as positive electrode and Li metal as the negative electrode, respectively. Although large theoretical capacity (1,672 mAhg-1) of the sulfur active material is expected as advantage, formation of Li dendrites at the Li metal surface during charge process is concerned as serious problem. In this study, we applied a negative electrode with Si to suppress the precipitation of Li dendrites. The theoretical capacity of Si is extremely high at 4,200 mAhg-1 and high energy density can be expected. However, Si has low cycle performance owing to their volume changes with Li+ insertion and desorption. In this study, several cells ([Li | 1M-LiFSI EC/DEC(=3/7) | x wt%-Si/C6] ) using nano-Si mixed electrodes with C6 ( x wt%-Si/C6 (x=5,10,25,50) ) were prepared and evaluated.
As example, showing how the 5wt%-Si/C6 electrode is fabricated. C6:Si:Acetylene Black:PVdF was mixed into the NMP solvent at a weight ratio of 81:4:7:8. The mixed slurry was applied onto copper foil and dried at 353 K. The 5wt%-Si/C6 electrode was punched to φ 16 mm and pressed with a uniaxial force. [Li| 1M-LiFSI EC/DEC(=3/7) | x wt%-Si/C6] cells were prepared and investigated by charge-discharge test at 303 K.
Fig. 1 shows the charge-discharge profiles at the first cycle of the [Li| 1M-LiFSI EC/DEC(=3/7) |x wt%-Si/C6] (x=5,10,25,50) cells (a) and the relationship between the number of cycles and discharge capacity (b) . The initial discharge capacity was higher than the theoretical capacity of C6 (ca. 360 mAhg-1). However, remarkable decrease in discharge capacity is confirmed in accordance with an increase in the mixing amount of Si. Miniaturization might be occurred due to the volume change of Si during the charge-discharge reaction. As a result, the reaction at the electrode/electrolyte interface should be degraded. Irreversible reactions might be occurred after 2nd cycle. In addition, the lowest discharge capacity was obtained at 10wt%. As a result, isolation of active material was also suggested. Therefore, it is necessary to consider improving the cycle characteristics by the use of additives and improvement of the negative electrode itself. In the presentation, we will report for improvement methods of charge-discharge properties, such as new binder and composites with electric conductive additives.

Figure 1
Comparative Study to Investigate the Role of SEI Layer on the Formation of Dendrites on Lithium, Sodium and Zinc Metals
Authors: Gregory Darrell , Capraz Omer Ozgur 
Published: July 2021

The huge theoretical capacities of metal anodes provide the potential for high energy density batteries that could have widespread applications in consumer devices. However, metallic anodes are plagued by challenges caused by the formation of unstable solid electrolyte interphase (SEI) layers, surface pitting, and dendritic plating morphologies leading to reductions in cycle life, low Coulombic efficiencies, and potential safety hazards. There currently exists a gap in understanding within the literature concerning the nucleation and morphology growth of dendrites upon metallic anodes during cycling. These dendritic morphologies lead to increased SEI layer formation, generation of “dead” metal which is no longer is physical or electrical contact with the electrode, and the potential for internal short circuits. So far, these drawbacks have prevented the widespread implementation of metallic anodes in secondary batteries. A better understanding of when dendrites nucleate and how plating morphologies evolve over cycling is needed for increasing reversibility of metallic anodes and facilitating next-generation battery technologies such as metal-air and metal-sulfur batteries.
In this study, we employed various electrochemical methods including galvanostatic cycling and impedance spectroscopy as well as imaging tools such as scanning electron microscopy to investigate the dendrite formations on Li, Na and Zn metals. Herein, we compare the performances of symmetric cells comprised of three metals M (Li, Na, and Zn) in analogous perchlorate (M(ClO4)x) electrolytes and draw connections between voltage profile variations and metal morphology evolution using SEM. These 3 metal anodes where chosen owing to their range of reactivities, electrons involved in their charge transfer reactions, SEI layer composition, and electrolyte compatibilities. Additionally, recent research based on modeling the onset of lithium dendrite growth as a diffusion-limited process using Sand’s equation has correlated the appearance of lithium dendrites to the reduction in Li + ion concentration at the lithium-SEI interface to zero. This hypothesis has been further evaluated by comparison of lithium electrodeposition in an organic electrolyte (wherein an SEI layer is formed) to zinc electrodeposition in an aqueous electrolytes (which involves the formation of a minimal SEI layer) using a custom 3-electrode cell. The results of this study provide insights into the analysis of symmetric cell voltage profiles and the nucleation mechanism of dendrites during charging.
Reference Systems for Lithium Sensors in Molten Alloys
Authors: Nel-lo Marc , Colominas Sergi , Abella Jordi 
Published: July 2021

Tritium is one of the required elements in future fusion reactors. This hydrogen isotope has to be continuously produced to supply the fusion reactor. Tritium can be obtained from the fusion reaction of lithium 6. Because of that, future fusion reactors are designed to have a tritium breeding module surrounding the reactor. One of the breeding blanket designs that has been proposed is based on lead-lithium eutectic melt [1]. Lithium monitoring in the breeding blanket is of great importance for the performance of the reactor. A deviation from the eutectic composition can cause a substantial change in tritium production.
To control the lithium dosage needed and keep the adequate composition in the melt, online lithium measurements will be required. For this purpose, lithium probes must be designed to withstand the high temperatures of the breeding modules (~400 ºC) and the chemical reactivity of lithium. The constructed sensors need to be tested at different lithium concentrations to determine their viability and range of application.
Sensors based on solid-state electrolytes have several advantages: stable compounds which can withstand the harsh chemical environment of the melts, their ionic conductivity tends to increase with the temperature [2] and the output signal (cell potential or electrochemical current) is easy to measure. Lithium conducting electrolytes for molten metals are under development at the Electrochemical Methods Laboratory at Institut Quimic de Sarria (IQS), Barcelona. Its qualification and performance are being tested.
In this work, Li6BaLa2Ta2O12 [3], a lithium-ion conducting solid-state electrolyte, has been used to develop potentiometric probes capable of measuring Li in molten Pb-Li alloys. As working electrode, Pb-Li alloys whose concentrations were between 3at% and 17at% Li were used. As reference electrode, Sn-Li and Pb-Li alloys were tested and compared. In these alloys, Li at% composition was kept constant during the whole experiment. Potentiometric measurements were performed at three different temperatures: 400 ºC, 500 ºC, and 600 ºC. Experimental data were in good agreement with theoretical calculations.
[1] F. De Schutter, J. Dekeyser, J. Luyten, H. Tas, Electrochemical sensors for oxygen and lithium detection in Pb17Li, Fusion Eng. Des. 14 (1991) 241–248. https://doi.org/10.1016/0920-3796(91)90008-E.
[2] V. Thangadurai, S. Narayanan, D. Pinzaru, Garnet-type solid-state fast Li ion conductors for Li batteries: critical review, Chem. Soc. Rgev. 43 (2014) 4714. https://doi.org/10.1039/c4cs00020j.
[3] M. Nel-lo, S. Colominas, J. Abellà, Lithium conducting ceramics for future electrochemical sensors in molten metals, Fusion Eng. Des. (2019). https://doi.org/10.1016/j.fusengdes.2019.02.043.
(Invited) Against the Odds: A High Power Mg Battery
Authors: Mohtadi Rana , Tutusaus Oscar 
Published: July 2021

To enable societal decarbonization, battery technologies that meet the application requirements in terms of safety, cost, energy density, performance reliability and sustainability are needed. Since commercially available battery technologies are not capable of meeting these demands, global research efforts have been increasingly focused on alternative battery chemistries such as those utilizing high capacity metal anodes such as Li and Mg. The main issue in Li metal batteries results from the highly reactive and dendrite prone Li metal, a challenge that is considerably relieved in rechargeable Mg metal batteries. However, Mg batteries suffer from sluggish discharge/charge kinetics caused by strong Mg2+ interaction with solvents and host solid state structures. [1,2,3]. Efforts have focused on improving Mg2+ diffusion in cathodes, whilst the impact of Mg ion coordination in the electrolyte on enabling or prohibiting the electrode function has received very little attention.[4]. Herein, we will discuss our recent efforts toward overcoming these issues through a tailored weakly coordinating electrolyte and a kinetically favored cathode that circumvent the issue of poor Mg ion diffusion.[5]

References

[1] Choi, J. W., Aurbach, D. Nature Reviews Materials 1, 2016, 16013, 1.
[2] Mohtadi, R., Orimo, S. Nature Reviews Materials, 2016, 2,16091, 1311.
[3] Mohtadi, R., Mizuno, F. Beilstein J. Nanotechnol. 2014, 5, 1291.
[4] Kar, M., Tutusaus, O., MacFarlane, D.R., Mohtadi, R. Energy & Environmental Science, 2019, 12, 566.
[5] Dong H., Tutusaus O., Mohtadi R., Yao. Y. et al, Nature Energy, 2020, 5, 1043.
Solvation, Speciation, and De-Solvation Penalties in Multivalent Battery Electrolytes
Authors: Hahn Nathan T , Landers Alan , Zavadil Kevin R 
Published: July 2021

Although substantial effort has been applied to the development of new multivalent liquid electrolytes for next generation batteries, an improved understanding of how the solvation environment controls the properties of these electrolytes is needed. Most working electrolytes for Mg2+ and Ca2+ systems utilize low permittivity solvents, namely ethers, which enable the high charge density of the divalent cation to exert significant influence on the surrounding solvation environment. These effects lead to non-intuitive concentration-dependent speciation and significant ion correlations even when employing “weakly coordination” anions. In this presentation we describe the solvation environments of critical exemplar systems based on Ca2+, Mg2+, and Zn2+ working cations using complementary techniques, including dielectric relaxation spectroscopy and modeling. In select cases we connect these solvation details to electrochemical desolvation barriers through temperature-dependent impedance spectroscopy. Through these investigations we address critical questions regarding the magnitude and tunability of the dication desolvation penalty during metal deposition and/or cathode insertion.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.