bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonflammable Ionic Liquid-Based Quasi-Solid-State Electrolytes for Highly Safe Sodium-Ion Batteries
Authors: Ban A-Hyeon , Park Myung-Soo , Park Tae-Hyun , Veerasubramani Ganesh Kumar , Kim Dong-Won
Published: July 2021

Because of the depletion of fossil fuels and increasing demand for sustainable energy, lthium-ion batteries (LIBs) have been considered one of the promising power sources for electric vehicles and other energy storage systems. However, increasing market demand for LIBs and limited lithium resources have caused a significant rise in cost of lithium sources. Thus, sodium-ion batteries (SIBs) have been considered a promising alternative to LIBs due to the natural abundance and low cost of sodium resources. However, like LIBs, conventional liquid electrolytes containing organic solvents are highly volatile and flammable, which causes safety problems such as fires and explosions. In this respect, ionic liquids (ILs) can be promising solvents for SIB electrolytes because of their attractive properties such as non-flammability, low volatility and exceptional electrochemical stability. Quasi-solid-state electrolytes (QSEs) have also received considerable attention to overcome the safety issues by avoiding leakage of organic solvents. Furthermore, they possess high ionic conductivity and superior flexibility. In this study, we report an IL-based QSEs with high ionic conductivity (1.5 mS cm-1) and non-flammability. The QSEs were prepared by in-situ thermal curing of boron-centered cross-linkers (BCs) in the IL-based electrolyte. Because the BC has anion-trapping boron moieties, it can promote the ionic mobility of Na+ in the QSE. As a result, the sodium cell employing the QSE exhibited stable cycling performance and enhanced safety.
Identifying Ionic and Polar Covalent Bonds in Superionic Metal Halides
Authors: Garcia Oskar Kenyatta , Aleman Johana Dolores , Adelstein Nicole
Published: July 2021

Solid state batteries are the future of energy storage due to their improved stability and energy density. Before they can rival the liquid-based batteries of today, however, significant improvement in ionic conductivity must be achieved. In pursuit of these improvements the bond character of AgI and other metal halides were simulated and analyzed. Maximally localized Wannier Functions from Quantum Espresso and Wannier 90 were used to calculate the electronic structure of AgBr, AgI, CuCl, CuI, and CuBr with four different crystal structures at multiple temperatures. Python and the Atomic Simulations Environment were used to identify diffusing cations, the angles between each interacting cation-anion bond and their bond types, ionic or polar-covalent. To illustrate the correlation between ionic diffusion and bond character, the angles and bond type of only the diffusing cations were isolated for graphical analysis. Understanding this correlation will lend insight into conductivity and enable the engineering of faster conductive crystals.
Composite Protective Layer Composed of Polymer and Ceramic for Protecting Li Metal in All-Solid-State Li Battery
Authors: Kim Ji-Wan , Woo Hyun-Sik , Lee Bo-Hyung , Kim Dong-Won
Published: July 2021

Various anode materials for rechargeable Li batteries, lithium metal is an ideal one for high energy density Li batteries. However, the Li-metal anode has severe safety problems and inferior performance in liquid electrolyte-based cell, due to the growth of Li dendrite and side reactions between Li and electrolytes. Use of solid-state electrolytes can solve the safety issues as well as suppress the Li dendrite growth. Solid polymer electrolytes have high flexibility and good interfacial contacts with electrodes. However, the mechanical strength of polymer is not enough to block Li dendrite growth. In the case of oxide-based inorganic electrolytes, they exhibit high ionic conductivity and good mechanical strength. Nevertheless, these inorganic electrolytes are not suitable for all solid-state battery, because their hard and brittle nature results in poor interfacial contacts with electrodes. In this work, we prepared a protective layer composed of ion-conductive polymer and inorganic materials onto the Li metal. It suppressed the lithium dendrite growth and reduced the interfacial resistance between solid electrolyte and lithium electrode. The electrochemical characterization of the protective layer was performed by DC polarization and electrochemical impedance spectroscopy. The solid-state Li/LiNi0.6Co0.2Mn0.2O2 cells was assembled with protected Li anode and solid electrolyte, and their cycling performance was evaluated.
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.
Ambipolar Gas Sensing Behaviors for Collection of Two-Dimensional Data from a Single Device
Authors: Kwon Hyunah , Kim Jong Kyu
Published: July 2021

An electronic nose (e-nose), an array of different individual chemiresistive sensors, has been proposed to mimic olfaction system of mammals. The e-nose provides a unique pattern for each gas species, which enables one to distinguish gases and their concentrations. Therefore, it demands as much reliable data as possible to improve gas selectivity. Increasing the number of constituting sensors allows to collect massive data, thus gives more chances to reduce errors, but this suffers from the complex and high-cost fabrication. More economical solution is collecting highly-distinguishable data from each sensor, which can produce more reliable results with reduced errors. In this presentation, we propose a new concept of collecting two-dimensional response data by making a single device show ambipolar sensing behaviors, thus, both p-type (the resistance increases in oxidative gases) and n-type (the resistance decreases in oxidative gases) sensing behaviors. The proposed concept utilizes the response direction (sign of the gas response) as well as the response amplitude, differentiated from other methods that produces monotonous data from each sensor by reading only the response amplitude.Firstly, we have demonstrated the ambipolar gas sensing behaviors in diode-type device; p-type NiO/n-type SnO2 diode, and NiO/Ti/Au Schottky diode. The ambipolar behavior is attributed to the predominant modulation of heterojunction barrier. Our unique device architecture has a single well-defined heterojunction formed by vertically aligned nanostructures and electrodes in a top-bottom configuration, facilitating the heterojunction barrier modulation. We also show the ambipolar sensing behavior in an organic thin-film transistor (OTFT)-based gas sensor that can operate in both n-channel and p-channel modes depending on the gate bias. Indeed the ambipolar OTFT-based gas sensor produces two-dimensional data depending on the gate biases. Our result reveal that the proposed ambipolar sensing concept allows the collection of two-dimensional data from a single device in a reliable manner, which can significantly contribute to enhance gas selectivity of e-nose.
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.
Ion Dynamics and Charge Transport in Imidazolium Chloroaluminate Ionic Liquids
Authors: Cosby Tyler , Durkin David P. , Mantz Robert A , Trulove Paul C.
Published: July 2021

Imidazolium-based chloroaluminates were the first widely studied room-temperature ionic liquids. Now, following 25 years of intense study of ionic liquids with less reactive anions, researchers are beginning to rediscover chloroaluminates, and other halometallate ILs, because they possess potentially advantageous properties that hold significant promise for applications such as energy storage, electrodeposition, and chemical synthesis. The majority of work characterizing the imidazolium-based chloroaluminates was conducted more than 25 years ago and focused on physical property measurements across limited compositions and/or narrow temperature/frequency ranges. In this study, we employ broadband dielectric spectroscopy, rheology, and differential scanning calorimetry to investigate ion dynamics and charge transport in a series of 1-alkyl-3-methylimidazolium chloroaluminates over much broader frequency and temperature ranges than these prior studies. The influence of cation chemical structure on the time-scales of ion-hopping, structural relaxation, and interfacial polarization associated with mesoscale solvophobic aggregates will be compared with other classes of aprotic imidazolium ionic liquids to highlight important differences observed for chloroaluminates. Finally, the influence of the relaxation time-scales on transport properties including dc ionic conductivity, zero-shear viscosity, and static dielectric permittivity will be presented. These new, in-depth studies, are focused on developing underlying structure-property relationships that are critical to realizing the full potential of chloroaluminate ionic liquids as electrolyte systems.
Elucidating Ionic Mobility in Multivalent Spinel Oxides
Authors: Murphy Megan , Alexander Grant C. B , Hirmiz Mark , Bayliss Ryan D , Tucker Matthew G , Cabana Jordi
Published: July 2021

With lithium-ion batteries seemingly reaching their developmental limits, researchers are exploring new chemistries to obtain the higher energy densities needed for electric vehicles to become more competitive for universal market adoption. Batteries based on Mg chemistries could achieve these goals. Oxides with a spinel structure are predicted to provide a favorable combination of properties to function as attractive magnesium cathodes; however, traditionally, Mg2+ intercalation suffers from sluggish mobility. Theory has predicted the energy barriers for the Mg2+ hops between tetrahedral sites via the vacant octahedral sites are low enough to enable sufficient room temperature transport. Experimental studies have shown potential Mg2+ migration at comparable timescales. While the activation barriers could be extracted, the path followed by the Mg2+ cation during a hop remains to be elucidated.

To better understand the trajectories for multivalent ion mobility in spinel oxides, variable temperature neutron diffraction and pair distribution function (PDF) are used to examine the average and local structure. Reverse Monte Carlo (RMC) profiling is then used to map the ionic pathways via large-box modeling of the crystal structure. Further contrast is provided by studying similarly structured samples where hopping is predicted to face higher activation barriers than Mg and, thus, show slower migration. Insight into how ion mobility is achieved in spinel structured oxides will better inform the design of new battery cathode host structures and electrolytes to help push Mg batteries into commercialization.
Direct Casted LLZO-LITFSI Composite Solid-State Electrolyte for Lithium Ion Batteries
Authors: Zhang Sanpei , Jansen Andrew N. , Lu Wenquan
Published: July 2021

All-solid-state batteries (ASSBs) based on solid state electrolytes (SSE) has a promising future for safer lithium ion batteries (LIB) with high energy density. However, it has been challenging in large-scale fabricating an SSE separator with transport properties and comparable thickness to a traditional polypropylene separator used in lithium-ion batteries. This problem is especially exaggerated with oxide-based solid electrolytes, such as Li7-3xAlxLa3Zr2O12 (LLZO), where thin films with micrometer scale in thickness using scalable techniques have not been realized.

LLZO SSE separator is commonly made by fabricating pellet and followed by sintering. The resulting film must be thick enough to provide reasonable mechanical strength. However, the thick SSE separator will cause high resistance and low energy density. Here we present a direct casting technique to coat ultrathin LLZO-LITFSI composite electrolyte on the LiFePO4 cathode. Through this technique, the electrolyte layers with different thickness ranging from 50 to 150 µm were prepared and studied electrochemically in ASSB using lithium as the anode. Without any further process and treatment, the ASSBs show a stable cycling performance with a reversible capacity >150 mA h/g (~90% of the theoretical value). This work provides a potential scale-up strategy to manufacture stable and ultrathin garnet-based SSE for all-solid-state batteries.

Acknowledgement

We gratefully acknowledge the support from the U.S. Department of Energy's Vehicle Technologies Office. This work is conducted under the Cell Analysis, Modeling, and Prototyping (CAMP) Facility at Argonne National Laboratory. Argonne National Laboratory is operated for DOE office of Science by UChicago Argonne, LLC, under contract number DE-AC02-06CH11357.
High-Performance Composite Polymer Electrolyte Membranes for Solid-State Lithium-Metal Batteries
Authors: Mehraj Ud Din Mir , Fischer Susanne Maria , Kuhnert Eveline , Häusler Michael , Trimmel Gregor , Slugovc Christian , Rettenwander Daniel
Published: July 2021

Ceramic-polymer composite electrolytes are among the strong contenders for the development of safe and high-energy density solid-state Li-metal batteries (SSLB). Current composite electrolytes suffer, however, from low conductivity and thermodynamic instability versus cathode materials1-3. In order to overcome the current limitations, we report the preparation of electrolyte membranes based on lithium garnet (LLZO) nanowires synthesized via electrospinning technique, poly (ethylene oxide) (PEO) and a sulfonic-based plasticizer enabled with high Li-ion conductivity of 0.1 mS cm-1 at room temperature. The fabricated flexible membranes show improved electrochemical performances. For example, the cyclic voltammetry results confirm the electrochemical stability of the developed electrolyte membrane in a voltage window of 3 V to 5.5 V that potentially enables utilization of high voltage cathodes such as LiCoPO4. To extend, the electrochemical stability towards low voltage to enable the use of cathode materials operating in a larger or lower voltage range, we engineered the lithium metal surface by a thin layer of Li3N layer that stabilized the developed membranes down to 1.5 V. Integration of the developed electrolyte membranes with high specific capacity cathodes could potentially enable the next generation Li-metal batteries with high energy density.

References:

(1) Croce, F.; Appetecchi, G. B.; Persi, L.; Scrosati, B. Nanocomposite Polymer Electrolytes for Lithium Batteries. Nature
1998, 394(6692), 456-458. https://doi.org/10.1038/28818.

(2) Kuhnert, E.; Ladenstein, L.; Jodlbauer, A.; Slugovc, C.; Trimmel, G.; Wilkening, H.M.R.; Rettenwander, D. Lowering the Interfacial Resistance in Li6.4La3Zr1.4Ta0.6O12|Poly (Ethylene Oxide) Composite Electrolytes. Cell Rep. Phy. Sci.
2020, 1(10), 100214. https://doi.org/10.1016/j.xcrp.2020.100214.

(3) Choudhury, S.; Stalin, S.; Vu, D.; Warren, A.; Deng, Y.; Biswal, P.; Archer, L. A. Solid-State Polymer Electrolytes for High-Performance Lithium Metal Batteries. Nat. Commun.
2019, 10(1), 1-8. https://doi.org/10.1038/s41467-019-12423-y.

Acknowledgement:

The financial support by the Austrian Federal Ministry for Digital and Economic Affairs, the National Foundation for Research, Technology and Development and the Christian Doppler Research Association (Christian Doppler Laboratory for Solid-State Batteries) and the Austrian Science Fund (FWF) (project no. P25702) is gratefully acknowledged.
(Invited) Entropy-Enhanced Ion Transport in Solid Electrolytes
Authors: Hu Yan-Yan
Published: July 2021

Long-range ion transport is composed of microscopic steps of ion migration, which is governed by local structures and interactions of the charge carriers with their surroundings. Therefore, understanding the local environments of conducting ions and their impact on ion dynamics and transport pathways are critical to design of high-performance solid electrolytes. We have synthesized and studied a variety of Li superionic conductors. Systematic solid-state nuclear magnetic resonance (NMR) investigations, complemented by pair distribution analysis (PDF) and DFT/MD simulations, have revealed that entropies in structures, compositions, and Li-coordination play a key role in determining ion hoping frequencies, jumping distance, transport pathways, and activation barriers. Via maximizing these entropies, “liquid-like” Li-sublattice is produced with a flattened energy landscape yielding extremely low activation barrier for ion transport. A few such examples will be discussed, including glass, ceramic, and glass-ceramic composites.
Improving Cell Resistance and Cycle Life with Solvate/Thiophosphate Hybrid Electrolytes in Lithium Metal and Lithium Sulfur Batteries
Authors: Gewirth Andrew A. , Philip Maria , Shin Minjeong
Published: July 2021

Solid electrolytes (SEs) have become a practical option for lithium ion and lithium metal batteries due to their improved safety over commercially available ionic liquids. The most promising of the SEs are the thiophosphates whose excellent ionic conductivities at room temperature are comparable to those of the commercially-utilized ionic liquids. Hybrid solid-liquid electrolytes exhibit higher ionic conductivities than their bare solid electrolyte counterparts due to decreased grain boundary resistance, enhanced interfacial contact with electrodes, and decreased degradation at the interface.

In this study, we evaluate a series of hybrid electrolytes made from a ‘solvate’ electrolyte in both Li-Li symmetric cells and in a full cell with a Li2S cathode relative to their bare Li/SE/Li counterparts. Interestingly, hybrid electrolytes made by combining HFE-modified solvates and SE exhibit all the benefits of the interlayer modified SEs, without the necessity of pellet manufacture. The solvate-integrated cathode layer is additionally beneficial for achieving high active material utilization, maintaining intimate interfacial contact, and providing buffer space for volume contraction and expansion. The hybrid Li2S cell exhibited superior cycling performance compared to the solid-state cells in terms of Li2S loading, Li2S utilization, and cycling stability. Finally, we discuss the use of hybrid and high concentration electrolytes to enable other cathode chemistries, particularly those involving conversion.
Local Solvation Modulates Activity of Covalent C−F Bonds in Fluorinated Electrolyte Additives
Authors: Gao Haining , Gallant Betar M.
Published: July 2021

Fluorinated reactants that enable fluoride bond cleavage, either in electrolytes or cathodes, are receiving increased research attention because of the formation of highly stable decomposition products (e.g. LiF), which also allows large Gibbs free energy change. Electrolytes using fluorinated solvents or additives (e.g. fluoroethylene carbonate (FEC), methyl 2,2,2-trifluoroethyl carbonate (FEMC), and liquefied CH3F) were shown to be able to effectively increase Li cyclability by forming LiF rich solid electrolyte interphase (SEI) on Li. In addition, conversion type Li battery cathodes, such as transition-metal fluorides (MFy, M=Fe, Co, Ni, Cu, y=2, 3) and CFx, can deliver high energy densities through fluoride bond reduction reactions. However, the strong electronegativity of fluorine making most of the fluoride bonds highly stable (i.e. hard to break), which limits their applications in electrochemical systems. Therefore, fundamental understanding of how to modulate fluoride bond strength to unlock activity is of vital importance. Herein, we use perfluoroalkyl group (RF)-containing liquid reactants as model systems to demonstrate that the covalent C−F bonds in RF, which were generally believed to be extremely difficult to reduce, can be unlocked through combined reactant-electrolyte design, with the electrolyte playing a central role in governing activity. The interaction between solvent and fluorinated reactants, such as solvation effects and formation of hydrogen bonds, can alter the electron density distribution along the carbon-fluorine skeleton and weaken fluoride bond strengths as indicated by nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) calculations. As a result, the reduction potential (from galvanostatic measurements for Li cells) can be dramatically increased from < 2.0 V to > 2.9 V vs. Li/Li+ through modulation of the solvent. In addition to activating electrochemically-active pathways, solvent molecules also need to exhibit proper polarities to allow both high miscibility (requiring low polarity), and Li salt solubility (requiring high polarity). Other electrolyte design aspects that can direct the reduction activity of highly fluorinated reactants will also be discussed, including fluoridation of solvent molecules, Li salt dissociation energy, and reactant/salt ratio. These understandings on tuning fluoride bond strength via electrolyte−reactant interactions will open up new design opportunities for fluorinated electrolyte components, either solvents or additives, for Li cells with high cycle stabilities, as well as high-energy Li primary battery with liquid cathodes.
Nucleation and Growth of Solid Electrolyte Interphase on Lithium Metal Batteries
Authors: Angarita Gomez Maria , Guo Ningxuan , Balbuena Perla B.
Published: July 2021

Lithium metal anode is considered a great candidate because of its high theoretical capacity and negative electrochemical potential. However, key factors like poor cyclability as well as the safety issues related to the uneven lithium electrodeposition, dendrite growth, and unstable solid electrolyte interphase (SEI) are keeping lithium metal batteries away from commercialization. Different attempts both experimentally and theoretically have been done to decode the exact structure and distribution of SEI, but due to the inherent dynamic behavior as well as the lithium reactivity, the exact structure of the SEI and its growth mechanisms are still unclear. In this study with the use of molecular simulation and computational chemistry tools, we investigate the initial nucleation and growth dynamics of different SEI components that provide us with thermodynamics and structural information about the nucleating SEI.

Different nucleation and growth mechanisms were studied for the SEI components including LiF, Li2O, and LiOH. An initial mechanism of nucleation is based on the assumption that a Li metal cluster represents a portion of the surface where inhomogeneous Li seeds are nucleating, we use ab initio methods to determine the preferential addition sites for OH or O radicals or fluorine anions. This mechanism allows the study of different structures of SEI in lithium-rich environments simulating initial stages of electrolyte decomposition and SEI formation. Multiple models are studied to understand the formation energies and structures for SEI nanocluster formation in which already formed fragments of SEI are joined together to study the formation of larger SEI clusters. Each of the different components of SEI reveals its preferential growth mechanisms showcasing different degrees of crystallinity and electron density distribution leading to a better understanding of the nucleation and growth of SEI.
Liquefied Gas Electrolytes for Wide-Temperature Lithium Metal Batteries
Authors: Yin Yijie , Yang Yangyuchen , Davies Daniel , Meng Ying Shirley
Published: July 2021

The momentum in developing next-generation high energy batteries calls for an electrolyte that is compatible with both lithium (Li) metal anode and high-voltage cathodes that is also capable of providing high power in a wide temperature range. Here, we present a fluoromethane-based liquefied gas electrolyte with acetonitrile cosolvent and higher, yet practical, salt concentration. The unique solvation structure observed in molecular dynamics simulations and confirmed experimentally shows not only improved ionic conductivity of 9.0 mS·cm-1 at +20°C but high Li transference number (tLi+=0.72). Excellent conductivity (> 4 mS·cm-1) was observed from -78 to +75°C, demonstrating operation above fluoromethane’s critical point for the first time. The liquefied gas electrolyte also enables excellent Li metal stability with a high average coulombic efficiency of 99.4% over 200 cycles at the aggressive condition of 3 mA·cm-2 and 3 mAh·cm-2. Also, dense Li deposition with an ideal Li-substrate contact is seen in the liquefied gas electrolyte, even at -60°C. Attributed to superior electrolyte properties and the stable interfaces on both cathode and anode, the performances of both Li metal anode and Li/NMC full cell (up to 4.5 V) are well maintained in a wide-temperature range from -60 to +55°C. This study provides a pathway for wide-temperature electrolyte design to enable high energy density Li-metal battery operation between -60 to +55°C.
Exploring the Ion Solvation Environments in Solid-State Polymer Electrolytes through Free-Energy Sampling
Authors: Sundararaman Siddharth , Prendergast David
Published: July 2021

Lithium-ion batteries are high energy density power sources that find uses in the automobile industry for electric cars and various portable devices like smartphones, laptops etc. There are strong motivations for developing solid-state electrolytes due to safety concerns associated with the combination of flammable liquid electrolytes and cell shorting due to lithium dendrite growth in current technology. A major issue with solid electrolytes is their low conductivity, which limits the power density (rate of charge/discharge), and possible loss of electrical contact due to anode shrinking. Lithium salts dissolved in poly(ether-acetals) are prime candidates for such electrolytes but the major challenge in improving the performance of these batteries is that the exact mechanism of the motion of the Li+ ions in such systems is not yet well understood. Our goal is to understand the underlying structural differences in the lithium coordination environments in these different systems and how this would affect the movement of the lithium ion from one coordination cage to another. This insight will allow us to suggest new compositions for electrolytes with improved performance for battery applications.

Molecular dynamics simulations using newly developed, accurate interaction potentials have helped elucidate possible mechanisms for various transport properties in these systems. The presence of a second coordination shell around the Li ion, observed in some of these systems, seems to distort the first coordination shell, creating a more open cage structure that may help facilitate transport in these polymers. Furthermore, this distorted coordination may also assist in the formation of a lower coordination transition state while the Li ions jump from one cage to another during diffusion. This may be similar to the pathways followed in solid-state transport - either during topotactic intercalation, as ions move from interstitial to interstitial site; or within materials with solid-solid phase transitions related to thermally induced rotations of complex anions. Free energy calculations further elucidate the relative stability of these different Li-ether coordination environments and the possible pathways to move between them (See figure 1 for example). Furthermore, to understand the associated correlations of glass transition temperature in these systems with microscopic chemical details like the polymer backbone chemistry, ion clustering and coordination, we study the trends in these different systems with extensive statistics from long time molecular dynamics simulations at different temperatures and compositions.

Figure 1
(Invited) Revisiting the Structure–Property Relationships in NaSICON Electrode and Electrolytes
Authors: Canepa Pieremanuele , Deng Zeyu , Singh Baltej , Gautam Gopalakrishnan Sai , Cheetham Anthony K. , Masquelier Christian
Published: July 2021

Sodium (Na) batteries are promising devices for smart grids and electric vehicles due to cost effectiveness arising from the overall abundance of and its even geographical distribution. The energy density of Na-ion batteries is limited by the positive electrode chemistry [1,2]. The Natrium Superionic CONductor (NaSICON) is known for its wide range of electrochemical potentials, its structural and thermal stability and its high conductivity [1-3]. The electrolyte analogue Na1+xZr2SixP3–xO12 (0 ≤ x ≤ 3) is stable toward other NaSiCON electrodes. Despite the share of research on NaSICONs, the structural and thermodynamic properties of these materials require better understanding.

I will analyse the thermodynamic properties of the Na1+xZr2SixP3-xO12 electrolyte by constructing its phase diagram, based on DFT and Monte Carlo simulations. I will discuss the phase diagram as a function of temperature and composition for the rhombohedral phase, which is common in Na3Ti2(PO4)3, Na3V2(PO4)3 and Na3Cr2(PO4)3 [4].

I will chart the chemical space of NaSICON electrodes NaxMM’(PO4)3 (M, M’= Ti, V, Cr, Mn, Fe, etc.), to analyse their thermodynamic stabilities and the intercalation voltages for Na+ ions in 28 distinct NaSICON compositions. I will discuss anomalies in previously reported experimental data in this diverse and important chemical space [5].

[1] Hong, H. Y.-P. Crystal structures and crystal chemistry in the system Na1+xZr2SixP3–xO12. Mater. Res. Bull.1976, 11, 173– 182.

[2] Goodenough, J. B.; Hong, H. Y.-P.; Kafalas, J. A. Fast Na+-ion transport in skeleton structures. Mater. Res. Bull.1976, 11, 203– 220.

[3] Boilot, J. P.; Collin, G.; Colomban, P. Relation structure-fast ion conduction in the NASICON solid solution. J. Solid State Chem. 1988, 73, 160– 171.

[4] Deng, Z.; Gautam, G. S.; Kolli, S. K.; Chotard, J. N., Cheetham, A. K.; Masquelier, C.; Canepa, P. Phase Behavior in Rhombohedral NaSiCON Electrolytes and Electrodes. Chem. Mater. 2020, 32, 18, 7908–7920.

[5] Singh, B.; Wang, Z.; Park, S.; Gautam, G. S.; Chotard, J. N.; Croguennec, L.; Carlier, D.; Cheetham, A. K.; Masquelier, C.; Canepa, P. A Chemical Map of NaSiCON Electrode Materials for Sodium-ion Batteries. J. Mater. Chem. A. 2020, 10.1039/D0TA10688G
Hybrid Solid State “Chaperone” Phases to Improve Solid State Sodium Electrolytes
Authors: Spoerke Erik D. , Gross Martha , Peretti Amanda , Percival Stephen , Small Leo
Published: July 2021

Solid state electrolytes exhibiting high sodium-ion conductivity are promising elements in the advance of high energy density, low temperature molten sodium, solid state sodium, and sodium ion batteries. Traditional solid state Na+-ion conductors, such as β”-Al2O3 or NaSICON are reserved for high temperature operations (~300°C), not only to access higher Na+-ion conductivity, but also to facilitate wetting of molten sodium on the solid electrolyte. Lowering the operating temperature to near or below the ~98°C melting temperature of sodium for new sodium battery applications leads to poor interfacial wetting of the molten sodium to the ceramic electrolyte, increasing interfacial resistance in the cell and ultimately producing poor battery performance. Here, we explore the application of hybrid interfacial “chaperone” phases that dramatically improve physical and charge transfer interfaces between a NaSICON ceramic electrolyte and a metallic sodium anode. Through the application of material such as tin to the NaSICON surface, in-situ transformation during electrochemical cycling leads to the formation of hybrid metallic/intermetallic/ceramic interphases that facilitate efficient sodium wetting and charge transfer. We observe that these chaperone phases dramatically lower cell-limiting interfacial resistance, facilitating higher battery cycling current densities and better overall battery performance. Continued optimization of such functional interphase materials promises new advances in emerging sodium batteries. 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.
Effects of Non-Solvating Fluorinated Solvents in Localized High-Concentration Electrolytes for Lithium Metal Batteries
Authors: Cao Xia , Gao Peiyuan , Ren Xiaodi , Zou Lianfeng , Engelhard Mark H. , Matthews Bethany E. , Hu Jiangtao , Niu Chaojiang , Liu Dianying , Arey Bruce W. , Wang Chongmin , Xiao Jie , Liu Jun , Xu Wu , Zhang Ji-Guang
Published: July 2021

High-voltage lithium (Li) metal batteries (LMBs) have been revived in recent years due to their high energy density. 1 However, their practical application is still hindered by the poor stability of the Li metal anode (LMA). The electrolyte is critical to the stability of LMA and the performance of LMBs, because the electrolyte formulation and structure determine the properties of the solid electrolyte interphase (SEI) formed on the LMA surface, which acts as a kinetic barrier for the continuous reaction between the LMA and the electrolyte. 2 High-concentration electrolytes (HCEs) and localized high-concentration electrolytes (LHCEs) have been recognized as good alternatives to replace state-of-the-art LiPF6/carbonate electrolytes and overcome the challenges in LMBs. 3 There are three basic components in the LHCEs: conducting salt, solvating solvent and non-solvating solvent (called diluent), forming a unique solvation structure, where highly concentrated salt-solvent clusters are distributed in the diluent. Here we investigated four types of fluorinated solvents in searching for the most suitable diluent for HCEs, including fluorinated ethers, fluorinated carbonate, fluorinated borate or fluorinated orthoformate. Their roles in the electrolyte solvation structures and effects on the electrode/electrolyte interphases will be discussed during the presentation together with battery performance. These systematic investigations and fundamental insights into LHCEs using different fluorinated solvents can guide further design of advanced electrolytes for high-voltage LMBs.

References:

Liu, J.; Bao, Z.; Cui, Y.; Dufek, E. J.; Goodenough, J. B.; Khalifah, P.; Li, Q.; Liaw, B. Y.; Liu, P.; Manthiram, A.; Meng, Y. S.; Subramanian, V. R.; Toney, M. F.; Viswanathan, V. V.; Whittingham, M. S.; Xiao, J.; Xu, W.; Yang, J.; Yang, X.-Q.; Zhang, J.-G., Pathways for practical high-energy long-cycling lithium metal batteries. Nature Energy
2019,
4 (3), 180-186.

Zhang, J.-G.; Xu, W.; Xiao, J.; Cao, X.; Liu, J., Lithium Metal Anodes with Nonaqueous Electrolytes. Chemical Reviews
2020.

Chen, S.; Zheng, J.; Mei, D.; Han, K. S.; Engelhard, M. H.; Zhao, W.; Xu, W.; Liu, J.; Zhang, J.-G., High-Voltage Lithium-Metal Batteries Enabled by Localized High-Concentration Electrolytes. Advanced Materials
2018,
30 (21), 1706102.
Electrophoretic NMR of Concentrated Electrolytes for Li-Ion Batteries: Understanding the Role of Solvent Motion
Authors: Halat David M. , Hickson Darby , Balsara Nitash P. , Reimer Jeffrey A.
Published: July 2021

In this work cation, anion, and solvent velocities are reported in concentrated Li-ion battery electrolytes using an electrophoretic NMR (eNMR) methodology. Recent computational studies suggest that in concentrated electrolytes, ion aggregation may lead to transport of Li+ in negatively-charged clusters, resulting in negative cationic transference numbers.1,2 Additionally, increasing ion–solvent coordination may lead to a significant non-zero solvent velocity. These unusual transport properties have important implications for fast-charging performance, but as of yet only limited experimental evidence exists for these phenomena.3 Pulsed-field-gradient (PFG) NMR experiments on their own give self-diffusion coefficients but do not report on the drift of charged species, or induced solvent motion; by running PFG under synchronized application of an electric field (i.e., eNMR), the sign and magnitude of electrophoretic mobilities can be determined with spectroscopic specificity. Through 7Li, 19F and 1H eNMR measurements on carbonate- and glyme-based concentrated electrolytes, we show average species velocities in good agreement with conductivity data, and also directly measure transference numbers in the solvent reference frame. eNMR may provide rapid screening of potential electrolytes at various concentrations to discern which systems (both liquid- and polymer-based) possess efficacious transport properties.

(1) France-Lanord, A.; Grossman, J. C. Correlations from Ion Pairing and the Nernst-Einstein Equation. Phys. Rev. Lett.
2019, 122 (13), 136001. https://doi.org/10.1103/PhysRevLett.122.136001.

(2) Molinari, N.; Mailoa, J. P.; Kozinsky, B. General Trend of a Negative Li Effective Charge in Ionic Liquid Electrolytes. The Journal of Physical Chemistry Letters
2019, 10 (10), 2313–2319. https://doi.org/10.1021/acs.jpclett.9b00798.

(3) Gouverneur, M.; Schmidt, F.; Schönhoff, M. Negative Effective Li Transference Numbers in Li Salt/Ionic Liquid Mixtures: Does Li Drift in the “Wrong” Direction? Physical Chemistry Chemical Physics
2018, 20 (11), 7470–7478. https://doi.org/10.1039/C7CP08580J.
Bulk XAS and Xes Spectroscopy Accessing the Origin of Lithium- and Manganese-Rich Cathodes Performances
Authors: Simonelli Laura , Ali Shehab , Sorrentino Andrea , Bresser Dominic , Passerini Stefano , Tonti Dino
Published: July 2021

Li-rich layered transition metal oxides Li[Li0.2Ni0.16Mn0.56Co0.08]O2 are attractive electrode materials providing high energy densities, relatively good cycling stability with reduced environmental costs [1]. However, their utility in many applications suffers from both voltage and capacity fade, most likely related to structural transformations and not yet fully understood.

The intrinsic complex nature of such materials strictly requires a multi-techniques approach to disentangle the several compositional degrees of freedom involved in their structure. In spite of being rich in Mn, not much attention is generally paid to the role of this component of such cathodes. In effect, it is important to access the Mn oxidation and spin states. Both such parameters are linked to the Mn size and magnetic interactions, and result key in defining the possible phases in which this cation is involved [1, 2-3], fundamental to control the reversibility of the reactions along cycling. Moreover, the Mn redox and spin state resulted correlated with Ni oxidation/reduction, also spatially, suggesting that strains induced on the Mn−O sublattice by the Ni oxidation are not negligible and can be used to control both the structure and the charge compensation mechanisms [2-3].

The results suggest that strategies can be elaborated to control the Li-rich NMC structure, hindering the spinel formation at the benefit of the electrode cycle life, and the charge compensation mechanism, accessing to an optimum O oxidation along the charge.

[1] Rozier, P.; Tarascon, J. M. Li-Rich Layered Oxide Cathodes for

Next-Generation Li-Ion Batteries: Chances and Challenges. J. Electrochem.

Soc. 2015, 162 (14), A2490.

[2] L. Simonelli et al. J. Phys.
Chem.
Lett. 10, (2019), 3359

[3] S. Ali et al. J. Phys.
Chem.
Lett. 12, (2021), 1195