bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Solid State Sulfonation of Poly(phenylene) on Mechanical Robustness and Proton Conductivity
Authors: Lee Michael , Senathiraja Thivani , Swan Bradley , Cornelius Chris
Published: November 2022

To meet ever increasing demands for energy worldwide, advances in both energy storage and energy conversion must be meet. Fuel cells, especially polymer electrolyte fuel cells (PEMFCs), and vanadium redox batteries problems include electrolyte instability and fuel crossover. Nafion® is the industry standard, but several drawbacks include low selectivity due to it bicontinuous morphology, large water uptake, and production cost. Several alternative ionomers have been investigated, however post sulfonated diels alder poly(phenylene) membranes have shown ideal properties with respect to selectivity, mechanical robustness, ionic conductivity, and thermal transitions. A homogeneous sulfonation has limits due to swelling above an IEC of 2.2 This study focuses on a solid-state surface modification in dilute and sub-ambient conditions via direct immersion in a chlorosulfonic acid solution followed by an exchange with a monovalent counter-ion. Planned thermal and mechanical studies include defining degradation temperature, toughness, and Young’s modulus in the monovalent form. Further property determination includes assigning experimentally determined diffusion coefficients for water vapor, proton conductivity, gas, and liquid water. Both in plane and through plane conductivity measurements are planned to be done at different degrees of water saturation. Lastly, chemical composition and structure will be determined through Fourier transform infrared spectroscopy- attenuated total reflectance studies and transmission and grazing-incidence small-angle x-ray scattering. Future studies include evaluation of fuel cell performance and further phase analysis through transmission electron microscopy.
(Digital Presentation) Fine Nitride Phosphors for Mini-LED Backlights
Authors: Xie Rong-Jun
Published: November 2022

Mini-LED backlights, combining color conversion materials with blue Mini-LED chips, promise traditional liquid crystal displays (LCDs) with higher luminance, better contrast and wider color gamut. As color conversion materials, Cd- or Pb-based quantum dots are usually toxic and unstable, and commercially available inorganic phosphors are quite stable and cheap, but they have a large size due to their synthesis at high temperature, and their quantum efficiency and reliability are size dependent. To make inorganic phosphors to be well combined with Mini-LED chips (usually 100 x100 μm in size) in the emerging Mini-LED backlights, the particle size of the phosphors needs to be reduced to several micrometers or sub-micrometers while the quantum efficiency remains unchanged. In this work, we prepared fine nitride phosphors by treating commercially available phosphors, including CaAlSiN3:Eu2+ and (Sr, Ba)2Si5N8:Eu2+, with ball milling, centrifuging and acid washing. The particle size of phosphors can be easily controlled by the milling speed, and the phosphors with a size varying from 0.5 to 15 mm were thus obtained. The samples remained the comparable quantum efficiency with the original ones even when their particle size was reduced to 2 μm as they contained less surface defects after acid washing. We demonstrated that red-emitting Mini-LEDs can be fabricated by combining the red phosphors with blue Mini-LED chips, which show higher external quantum efficiency, luminance and stability than those made by using quantum dots. It indicates that fine and high efficiency phosphors can be obtained by the proposed method in this work, and they have great potentials for use in Mini-LED displays.
(Digital Presentation) Red and Near-Infrared Emission of Eu2+ Doped Solid-State Phosphors for LED Applications
Authors: Xia Zhiguo
Published: November 2022

Owing to the unique 4f-5d transition, Eu2+ is one of the most commonly used activators in luminescent materials for phosphor-converted light-emitting diodes (pc-LEDs), and Eu2+-doped phosphors exhibit outstanding luminescence properties, including multi-color emission, adjustable bandwidth, excellent thermal stability as well as high luminescence efficiency. These attributes motivate scientists to find Eu2+ doped phosphors that can practically meet the various LED application requirements. In this talk, I will summrize our recent progresses to manipulate Eu2+ emission exhibiting red and near-infrared emissions under blue light excitation. One can expect and further adopt proper structural engineering strategies to tune the Eu2+ luminescence. Moreover, the state-of-the-art LED application including solid-state lighting and near infrared night-vision technologies will be also introduced based on these Eu2+ doped phosphors. We hope this talk will be helpful for controlling the photoluminescence by theory-structure-property relationships and guide scientists discover the next generation of Eu2+ doped phosphors for emerging applications.
(Digital Presentation) Growth of Mn4+-Activated Red-Emitting Photoluminescent Crystals
Authors: Ji Haipeng
Published: November 2022

Compared with Mn4+-activated polycrystalline phosphors in micro powder form, the Mn4+-activated red-emitting crystals with considerable size exhibit improved resistance to deterioration under water attack. Besides, large sized fluorescent crystal can be packaged on LED in the remote configuration. We recently developed a series of methods for growing Mn4+-doped red-emitting crystals which have different solubilities.

(1) For the fluoride hosts that have large solubility in acid solution such as (NH4)2SiF6, (NH4)2TiF6, K2TiF6, a series of centimeter-sized crystalline ingots were prepared by a cooling induced crystallization method (cooling from 20 °C to minus 40 °C). During cooling, the solubility decreases and the centimeter-scale Na2SiF6:Mn4+ ingots as well as the fluoride phosphors with similar physicochemical property including (NH4)2SiF6:Mn4+, (NH4)2TiF6:Mn4+ and K2TiF6:Mn4+ were successfully grown through the supersaturated crystallization process by cooling down.

(2) For the fluoride hosts that are slightly soluble such as BaTiF6, we firstly prepared BaTiOF4 as precursor, which is then mixed with K2MnF6 and gradually fluorinated in HF acid solution at room temperature. After a continuous feeding process, epitaxial growth of the BaTiF6:Mn4+ ended up with ingots up to a record-breaking length of 200−300 μm, which exhibit better water resistance than commercial K2SiF6:Mn4+ micro phosphor.

(3) For the oxide hosts that are insoluble such as MgAl2O4, we use the molten salt method, and by optimizing the type of molten salt to adjust the dissolution and migration of Mg2+/Al3+/Mn4+ ions in it, the MgAl2O4:Mn4+ crystals in tetragonal bipyramid shape with uniform size of 2−4 μm were prepared under relatively mild conditions at 950 °C. The phosphor exhibits a broadband emission peaking at 651 nm under the 450 nm excitation, which is the highest energy of the Mn4+
2E→4A2 transition energy in oxides.

Figure 1
(Digital Presentation) Cr-Doped High-Efficiency Broadband Near-Infrared Luminescent Materials
Authors: Song Zhen , Liu Quan Lin
Published: November 2022

Cr-doped high efficiency broadband near-infrared (NIR) luminescent materials have attracted huge research interests in food analysis, plant growth, night vision and biomedical imaging owing to their invisibility and characteristic absorptions by certain molecules. Transition metal element Cr3+ with [Ar]3d3 configuration serves as an ideal activator for broadband NIR emission due to the broad absorption bands in the blue and orange-red spectral regions, among which the blue band matches well with the commercial blue LED chips. Besides, the NIR emissions of Cr3+-doped phosphors are greatly affected by the crystal field strength of the matrix lattice. In the weak crystal field, the spin-allowed 4T2 → 4A2 transitions give out the preferable wide-band emissions. However, the NIR luminescence of Cr3+ encounters several problems aiming at further developments. The materials with main emission peak beyond 800 nm are lacking. Meanwhile, the quantum efficiency and thermal luminescence stability need improvement to fulfil the application requirements. Also, it remains a challenge to predict the Cr3+ luminescence by crystal-field theory theoretically. To address those problems, we introduce several high-efficiency Cr3+ doped materials with distinct crystal structures, such as SrGa12O19:Cr3+, LaMgGa11O19:Cr3+, LiInGe2O6:Cr3+, and Sr2ScSbO6:Cr3+, together with the structural confinement strategy to improve the NIR performance. The further research topic including the local structure is also discussed.
(Invited, Digital Presentation) Substituent Effect on Fluorescent Probes: Photophysical- and Electrochemical Properties and Their Application As Chemosensors
Authors: Lee Sunhee , Lee Yeeun , Han Won-Sik
Published: November 2022

Stimulus-responsive materials have great potential for sensing applications, and their photophysical- and electrochemical properties can be finely tuned as modifying molecular structure. In this presentation, two series of fluorescent probes, BF2dbm and CzPyr, will be introduced as nitro-explosive and acid chemosensors, respectively. Both series of compounds showed different sensing abilities, varying from electron-withdrawing to electron-donating abilities in the peripheral phenyl groups. The photophysical- and electrochemical properties of these compounds, along with density functional theory and time-dependent density functional theory calculations, are systematically investigated to study the structure-property relationships. For BF2dbm, the emissions in chloroform solution are quenched exponentially by adding o-nitroaniline, with quenching constants up to 17,800 M−1. For CzPyr, an evaluation of the emission properties in the solid-state revealed the photochromic activity, and reversibly switched on and off by controlling the pH conditions.
Enhanced Phase, Thermal and Aqueous Stability of the Embedded the CsPbI3 Ncs in Cs4PbI6 Ncs
Authors: Cho Han Bin , Im Won Bin
Published: November 2022

Increasing the stability of lead halide perovskites (LHPs) is required for integrating them into light-emitting devices. To date, most studies toward this direction have primarily concentrated on improving the chemical stability of green-emitting LHPs. In this work, red-emitting CsPbI3–Cs4PbI6 hybrid nanocrystals (NCs) were synthesized with a high photoluminescence (PL) quantum yield of ∼90%. Their hybrid structure was examined via structural (Rietveld) refinement analysis and transmission electron microscopy. Rietveld refinement also revealed that the black polymorph of CsPbI3 NCs is an orthorhombic perovskite rather than a cubic one. The thermodynamic stability of the CsPbI3 NCs in Cs4PbI6 matrices is enhanced in both solutions and films for up to several weeks. The enhanced stability of the embedded CsPbI3 NCs is attributed to the lowering of their Gibbs free energy, as determined on the basis of experimental data. Additionally, the hybrid NCs exhibit unprecedented emission stability—maintaining 65% of their original PL efficiency at 150 °C—and improved aqueous stability.
Ultra-Low Detection of Infectious Disease Nucleic Acid Biomarkers By a Visual Colorimetric Sensor
Authors: Syed Zia
Published: November 2022

The gold standard method for detecting nucleic acid markers is the polymerase chain reaction. However, this method demands high technical skills, labor-intensive, time-consuming, and expensive. Many resource-limited countries around the globe do not have access to such laboratory-based PCR tests. To address the global test needs of virus and other pathogen infections, as well as address the early biomarker detection of diseases. We have developed an affordable nanoparticle colorimetric sensor approach. In our system, the virus RNA marker is captured by the complementary oligonucleotide attached to low fouling gold-coated iron oxide nanoparticles. Further specificity is achieved through a second complementary hybridization probe conjugated with streptavidin-horseradish peroxidase labels. Visual colorimetry is performed using a chromogenic substrate allowing the visual conversion of the colorless solution to a blue color confirming a positive test. The intensity of the color is in direct correlation to the concentration of the virus RNA marker. We have successfully demonstrated attomolar detection in buffer and picomolar detection in real undiluted biofluids such as in neat human serum. Our ongoing efforts focus on saliva-based non-invasive detection with ultra-low capabilities, optimization of the assay, repeatability, and expanding this work for a multiplex detection format
An Electrochemical Activity Assay of Non-Electroactive Enzymes
Authors: Gerulskis Rokas
Published: November 2022

Enzymatic tools serve important functions in all areas of human life. Research aimed at comparing the catalytic rates of functionally overlapping enzymes of interest (EOIs) is hampered by expensive and time-consuming growth and purification procedures. Assaying the performance of already purified EOIs requires further laborious optimization. These assays are typically colorimetric and employ a downstream signal producing enzyme such as NADH-coupled dehydrogenases, which complicate assay optimization with their own unique chemical and pH requirements. Electrocatalysts such as 2,2,6,6-tetramethylpiperidine 1-Oxyl (TEMPO) have much broader pH ranges and substrate scopes (TEMPO oxidizing aldehydes and non-tertiary alcohols) than signal enzymes and output their catalytic rates directly as current density. The field of electrochemistry is also making strides in enzyme-electrode immobilization, with several works now reporting methods to anchor enzymes onto electrode surfaces directly from cell lysate, avoiding lengthy column-purification procedures.

This work proposes a hybrid electrolytic cell in which the catalytic rate of immobilized enzyme is quantified as current density produced by TEMPO-mediated oxidation of its products. The rate of production of carbon paper electrodes has been expedited and their functional area has been standardized through novel cutting and waxing procedures, demonstrating surface area coefficient of variation values up to an order of magnitude lower and production rates an order of magnitude higher than those of traditionally produced electrodes. Variation in electrode-loading of pyrene-anchored TEMPO has also been minimized, demonstrating current density variation identical to that of electrode functional area. Current work is investigating enzyme immobilization architectures employing electrode-immobilized DNA and Zinc-finger anchored enzyme to maximize enzyme loading, as well as enzyme-electrocatalyst reactivity to minimize background signal. In summary, we aim to develop an electrochemical assay of enzyme activity able to quantify the catalytic rates of a wide range of aldehyde and non-tertiary alcohol producing EOIs while minimizing the lengthy enzyme purification and assay optimization procedures of traditional colorimetric assays.
Mechanistic Insights into the Electrochemical Oxidation of Cyclohexane
Authors: Siboonruang Tana , Tang Maureen
Published: November 2022

The detrimental effects of CO2 emissions from fossil fuels and the decreasing cost of electricity have accelerated interest in electrochemical synthesis. Electro-organic synthesis offers a sustainable and cost-effective pathway for chemical manufacturing. This method has the potential to minimize greenhouse gas emissions, enhance reaction selectivity, and replace hazardous chemical reagents with electric current.

Electrochemistry enables alternative mild temperature and pressure pathways to traditional thermochemical reactions. An intermediate step to producing nylon 6,6 is synthesis of KA oil, a mixture of cyclohexanone and cyclohexanol, from cyclohexane. This reaction is limited by low conversion and high pressures. An electrochemical approach can introduce a more selective reaction pathway at more benign conditions. Although electrochemical cyclohexane oxidation to KA oil has been demonstrated in literature, its mechanism remains poorly understood. In this work, we elucidate the mechanism of electrochemical cyclohexane oxidation. We report the oxygen source (water vs. oxygen) and the role of the counter electrode reaction cyclohexane oxidation. Through analysis of side products and electroanalytical methods, we suggest a reaction pathway. In addition, we use chronoamperometry to demonstrate that electrode material affects cyclohexane conversion and recommend the optimal catalyst for this reaction.
Suppressing the Dark Current through Interfacial Modification Using Metal–Organic Framework Thin Film Grown with Layer-By-Layer Method
Authors: Duan Jiaxin , Hupp Joseph
Published: November 2022

Dye-sensitized solar cells (DSSCs) are promising photovoltaic devices and research was done in enhancing their efficiency so that they could be the potential alternatives to the p-n junction devices. Metal–organic frameworks (MOF) with porphyrin linkers as the photosensitizer have demonstrated their potential in preventing the aggregation of the dye over the transparent electrode surface. We aim to achieve the suppression of dark current by modifying the interface between the electrode and the photosensitizing film so that the efficiency can be further enhanced. To achieve this, we utilized the layer-by-layer growth method aiming for the control of the very layer(s) in between the indium tin oxide(ITO) electrode and the MOF layers. A change in the dark current produced by ITO/Insulation-layer/MOF system can be observed.
Me-N-C Electrocatalysts for Electrochemical CO2 Reduction to High-Value Products
Authors: He Yanghua , Weiss John Christian , Zelenay Piotr
Published: November 2022

The development of sustainable carbon-neutral energy technologies to mitigate greenhouse gas emissions has become imperative and urgent. Of special interest and importance in this context is the use of electricity from intermittent renewable energy sources (wind, solar) for electrochemical conversion of carbon dioxide (CO2) to easily storable and transportable value-added products: fuels and feedstock chemicals. Nanoparticles of non-precious metals, e.g., Cu, Sn, Co, show high activity for electrochemical CO2 reduction reaction (CO2RR) but suffer from poor selectivity, resulting in a mixture of products that require tedious and costly separation. Recently, transition metal- and nitrogen-doped carbon (Me-N-C) materials have been emerged as promising CO2RR catalysts thanks to their well-defined structures and good activity. However, their selectivity, while respectable for the generation of carbon monoxide (CO), is low for high energy-content products. A limited understanding of reaction pathways and degradation mechanism of Me-N-C catalysts for CO2RR has additionally stemmed a rational design of these materials.

In this presentation, we summarize our study of the activity, selectivity, and stability of Me-N-C (Me = Fe, Co, Ni, or Cu, etc.) catalysts for the CO2RR, focusing on the role of the local coordination environment at metal centers and metal-carbon substrate interactions. We also report the obtained bimetallic M1M2-N-C catalysts, designed to enable the formation of multi-carbon products through CO2RR and utilizing high surface-area three-dimensional carbon matrix as support for metal sites with improved CO2RR activity. The main objective of this work is to use Me-N-C catalysts to produce high energy-density chemicals, enhance mechanistic understanding, and bring CO2RR closer to practical applications.
Effect of Nitrogen Ligand Type on 3d Orbital Level Rearrangement of Cobalt Single Atom Catalysts
Authors: Jeong Taeyoung , Kang Joonhee , Kim Byung-Hyun , Kim Myeongjin
Published: November 2022

Transition metal single atom catalysts have recently emerged in acid oxygen evolution reactions (OER) due to their maximum atomic efficiency and high durability. Herein, we report a 3d orbital level rearrangement in square planar symmetry according to the ligand type of a cobalt single atom catalyst. We fabricate cobalt single atom catalyst supported on pyrrole type nitrogen doped crumpled graphene (Pyrrolic CoN4-CG) for acidic OER and it shows orbital rearrangement phenomenon because of their longer Co-N bond distance than pyridine type CoN4 sites. When pyrrole type nitrogen is introduced as a ligand of a cobalt single atom catalyst, the degree of oxidation during OER reaction is much greater than when pyridine type nitrogen ligand is introduced, which is confirmed by Operando X-ray absorption spectroscopy measurements. In addition, the reduction of OH- adsorption energy according to the orbital level rearrangement of Pyrrolic CoN4 and the change in the rate determination step are revealed by density functional theory calculations.
Influence of Fe Content in the Bifunctional Activity of LaFexCo1-XO3-δ Perovskite Catalysts for Zinc Air Batteries and Reversible Fuel Cells
Authors: Siddiqui Humera Khatoon , Waidha Aamir Iqbal , Kanbach Sabine , Kübler Markus , Palakkal Jasnamol Pezhumkattil , Haller Steffen , Clemens Oliver , Alff Lambert , Kramm Ulrike I.
Published: November 2022

Eco-friendly energy-storage systems are needed to lower the fossil-fuel dependence and environmental contamination. Among energy storage technologies, metal air batteries offer a good and cheap perspective for the energy supply in small devices. However, its efficiency is low due to the slow kinetics of key reactions namely oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). The same reactions occur in a reversible fuel cell. Perovskites have emerged as a promising candidate for alkaline condition due to the diversity in crystal structure, possibility of tuning electronic properties, low cost and earth abundance. Different catalytic descriptors for these ABO3-type systems are for instance eg orbital filling on B-site metals [1], high structural and chemical stability [2], oxygen vacancies [3], B-site metal oxygen covalency [4] and crystal structure [5]. Thus, a variation of the B-site is an effective strategy in order to enhance the catalytic properties [4][6].

In this work, LaFexCo1-xO3-
δ (x = 0 to 1) perovskites have been synthesized using a sol-gel approach and are characterized by several physicochemical techniques to identify the composition, structure and electronic state of iron and cobalt. We will discuss to what extent the activity depends on the descriptors as discussed above. Moreover, for our best performing material, its performance in Zn air battery was evaluated.

References:

[1] Suntivich, Y. S. Horn et al., Nat.
Chem.
3 (2011) 7, 546–550.

[2] Suntivich, Y. S. Horn et al., Science
334 (2011) 6061, 1383-1385.

[3] T. Mefford, K. J. Stevenson et al., Nat. Commun. 7 (2016) 11053.

[4] Duan, Z. J. Xu et al., Chem. Mater.
29 (2017) 24,10534–10541.

[5] Zhou and J. Sunarso, J. Phys. Chem. Lett. 4 (2013) 17, 2982–2988.

[6] Wang, Z. Feng et al., ACS Appl. Mater. Interfaces
11 (2019) 6, 5682-5686.

Figure 1
Reactivity of Metal Ions with Excess Electrons in Molten MgCl2-KCl Mixtures
Authors: Wishart James F. , Iwamatsu Kazuhiro , Layne Bobby , Halstenberg Philip
Published: November 2022

Molten salts are proposed as liquid fuels or coolants in a new fleet of molten salt nuclear reactors that would have operational and safety advantages over present reactor systems. Under those conditions, the salt will be exposed to high radiation levels, and understanding the chemical effects of radiolysis on the molten salt fuel or coolant is essential to reliable, efficient and sustainable reactor operation. Building this understanding begins with identifying primary salt radiolysis products and characterizing their reactivities, for which we perform high-temperature pulse radiolysis transient absorption spectroscopy at the BNL Laser-Electron Accelerator Facility. Salt mixtures containing monovalent and divalent cations are of particular interest because of their tunable Lewis acidity-basicity that can be used to control the solubility of dissolved metal ions in the reactor. Changing the MgCl2:KCl mixing ratio alters the absorption spectra of radiolytically-produced excess electrons, with increasing blue shifts related to the probable number of Mg2+ ions close to the cavity electron. These strong blue shifts imply significant changes in the electron’s energetics and reactivity that we quantify by measuring reaction kinetics with metal ion electron acceptors. This work was supported as part of the Molten Salts in Extreme Environments Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science.
(Invited) 20 Years of CO2 Capture By Ionic Liquids, Molecular Liquids, and Liquids in-between
Authors: Davis James H. , West Kevin N.
Published: November 2022

In 2002 we reported the first synthesis and use of a functionalized ("task-specific") ionic liquid for the reactive but reversible capture of CO2. Our original application target was the use of these salts in natural gas purification. However, in succeeding years considerable fervor grew up around us focused on accomplishing large-scale CO2 capture due to concerns about its contribution to global climate change, and that has since supplanted the former application as a major driver of our research. Recognizing that our early materials were likely prohibitively expensive for large scale use, we then spent five years devising new ones which could be made inexpensively from bulk commodity chemicals. In the time since, work with that class of salts, including the edible-in-principle salt choline taurate, has continued apace. These efforts have now resulted in systems which are being actively assessed by the Navy and NASA for closed-system removal of CO2 from breathing air, and which are being tested at pilot plant scale, in collaboration with Norton Engineering, for industrial emissions gas CO2 capture, as well as CO2 capture from ambient air. A brief discussion of the timeline of these developments will be presented, as will details about the ionic liquids currently being used in these tests and our results to date. In addition, we will briefly discuss the potential for using in-situ electrochemical reduction of CO2 in the 'loaded' ILs as a means to convert them into value-added products. Finally, we will also briefly comment on terminology as it relates to ionic liquids, molecular liquids, and liquids "in-between."

Figure 1
Understanding Structure-Property Relationships in Deep Eutectic Solvents (DESs)
Authors: Spittle Stephanie , Brackett William , Sangoro Joshua
Published: November 2022

Deep eutectic solvents (DESs) are an emerging class of highly tunable solvents with unique properties such as high solvent strength, wide electrochemical and thermal stability windows, nonflammability, and biodegradability/nontoxicity. These have given them potential as in many areas, including electrochemical technology applications like redox flow batteries and solar cells. However, they are held back by their relatively high viscosities and low conductivities. For this reason, it would be useful to understand how to improve these materials for target applications based off their molecular identity. Here, we use a variety of experimental techniques to study a series of choline-based DESs which are systematically varied by functional group and its position to examine the changes in local structure and dynamics and that effect on macroscopic properties. Generally, we observe that slight structural changes result in significant changes in the eutectic composition, viscosity, and dc ionic conductivity.
(Digital Presentation) Physicochemical Characterization of Sulfonate-Based Phosphonium Ionic Liquids
Authors: Tsunashima Katsuhiko , Hasegawa Shun , Okuno Yoshiharu , Yamada Hirohisa
Published: November 2022

Ionic liquids (ILs) have unique physicochemical properties such as favorable solubility of organic and inorganic compounds, relatively high ionic conductivity, no measurable vapor pressure, high thermal stability, low flammability, etc. ILs are also promising liquid materials available for various applications because their function can be easily controlled by changing the combination of cations and anions and by introducing substituents. Although many kinds of ILs have already been investigated, phosphonium cation based ILs have rarely been proposed. We have previously designed and synthesized the phosphonium ILs together with typical sulfonylamide-based anions such as bis(trifluoromethylsulfonyl)amide and bis(fluorosulfonyl)amide anions.1,2) On the other hand, interests in phosphonium ILs consisting of the other anions is increasing for diverse applications. In this work, we design and prepare the ILs based on tetrabutylphosphonium cation (P4444
+) together with various sulfonate-based anions (Fig. 1), characterizing their physicochemical properties as a new family of ILs.

The phosphonium IL was prepared by an aqueous neutralization reaction of tetrabutylphosphonium hydroxide with the stoichiometric amounts of various sulfonic acids. The obtained phosphonium ILs were isolated by water evaporation, and were dried in vacuo for at least 1 day. The physicochemical properties of ILs, e.g. density, viscosity, conductivity (ac impedance method) and thermal decomposition temperature (thermogravimetric analysis), were measured under argon atmosphere.

The phosphonium salts based on unsubstituted sulfonate anions such as SO3CH3, SO3CH2CH3 and SO3(CH2)2CH3 were white crystalline solids at room temperature, whereas both amino- and hydroxy- substituted sulfonate salts were viscous liquids at room temperature. All phosphonium salts obtained were hydrophilic. Table 1 summarizes the physicochemical properties of phosphonium ILs based on amino- and hydroxy-substituted sulfonate anions. These phosphonium ILs exhibited considerably high viscosities when compared to the previously published viscosity value of P4444-lactate IL (415 mPa s at 25 °C)3), which suggests that the electrostatic interaction between P4444 cation and the sulfonate anions is much stronger than those in the case of carboxylate-based phosphonium ILs. It should be noted that P4444-SO3(CH2)3NH2 obviously indicated not only the highest density but also the highest viscosity and the lowest conductivity, which might be due to the fact that the IL has the largest anion to give a significant van der Waals interaction.

Figure 1
Interplay of Local Dynamic Heterogeneity, Mesoscale Aggregate Dynamics, and Transport Properties of Imidazolium Ionic Liquids
Authors: Cosby Tyler , Durkin David P. , Mantz Robert A , Trulove Paul C.
Published: November 2022

Ion dynamics and charge transport in 1-methyl-3-octylimidazolium ionic liquids with chloride, bromide, tetrafluoroborate, tricyanomethanide, hexafluorophosphate, triflate, tetrachlorodialuminate, bis(trifluoromethylsulfonyl)imide, and heptachlorodialuminate anions are investigated by broadband dielectric spectroscopy, rheology and viscometry. A detailed analysis reveals anion and temperature-dependent separation of characteristic relaxation rates extracted from various representations of the dielectric spectra. The degree of separation is interpreted as an experimental signature of significant heterogeneity of the local ion dynamics associated with the structural glass transition, viscosity, and dc ion conductivity. It is found that the degree of dynamic heterogeneity correlates closely with the strengths of slow dielectric and mechanical relaxations previously attributed to the dynamics of mesoscale solvophobic aggregates. Increasing local dynamic heterogeneity correlates with an increase in the strength of the slow, aggregate dielectric relaxation and a decrease in the strength of the slow, aggregate mechanical relaxation. Accordingly, the local dynamic heterogeneity correlates with an increase in the static dielectric permittivities and a decrease in the contribution of aggregate dynamics to the zero-shear viscosities. These results are presented within a broader framework of current understanding of dynamics in ionic liquids and the interplay of dynamics, solvophobic aggregation, and charge transport in these technologically important systems.
(Digital Presentation) Dielectric and Vibrational Spectroscopic Study on Asymmetric Quaternary Phosphonium-Based Ionic Liquids
Authors: Matsumoto Mitsuhiro , Kazuki Takeuchi , Inoue Yohtaro , Tsunashima Katsuhiko , Yamada Hirohisa
Published: November 2022

Ionic liquids (IL) have a great potential of applications in electrochemical devices such as electrolytes for fuel cells. In particular, quaternary phosphonium cation-based ionic liquids (P-ILs) is much suitable due to lower viscosity and better ionic conductivity compared with corresponding quaternary ammonium cation-based ionic liquids (A-ILs). Over the past decade, fundamental properties of P-ILs have been investigated by viscometry, calorimetry, spectroscopy, calculation, and so on. However, little is known about molecular mechanism for such better potential of P-ILs. The present study aimed to reveal the relationship between molecular structure and macroscopic material properties of P-ILs in terms of alkyl chain asymmetry.

The P-ILs used in this study were prepared by quadrification of trialkylphosphine followed by ion exchange with bis(trifluoromethanesulfonyl)imide (TFSA) anions. We named P-ILs based on the number of alkyl chain length. For example, P2225 means triethyl(penta)phosphonium cation. In this study, we used P2225-TFSA, P2228-TFSA, and P222(12)-TFSA. We conducted temperature-variable broadband dielectric spectroscopy between 20 Hz and 100 MHz. We also carried out Raman spectroscopy (laser excitation at 532 nm) and THz spectroscopy.

The obtained complex dielectric spectra were dominated by (i) electrode polarization, (ii) ionic conduction, and (iii) reorientational relaxation, depending on the frequency and temperature. The spectra at the frequency regions between ionic conduction and reorientational relaxation were well-fitted with a Havriliak-Negami dielectric relaxation function, superimposed with a conductivity term. Thus, we determined both ionic conductivity (σdc) and relaxation time for structural relaxation (τHN) of ionic liquids. Although the σdc for all of the P-ILs used in this study exhibited similar Vogel-Fulcher-Tamman-type temperature dependence, the σdc slightly decreased with increasing the asymmetric alkyl chain length. Such temperature dependence was also observed in τHN, meaning that translational dynamics partly coupled with segmental dynamics. This result is consistent with that internal motion of the alkyl chains should depend on the chain length. Raman and THz spectroscopy provided an information on molecular structure (such as conformation) and inter- and intra-molecular interaction between anions and cations. In the presentation, we will describe the relationship of charge carrier transportation with ion conformations and intermolecular structures.
An Electrochemical Approach to Critical Materials Via Molten Salts and Ionic Liquids
Authors: Dai Sheng
Published: November 2022

Both graphite and rare-earth materials are considered by the US Department of Energy to be critical materials. Due to their widespread use as anodes in batteries and magnets in wind turbines, the demand for high purity graphite and rare earth elements for battery and clean-energy applications is expected to increase for the foreseeable future. Herein, an electrochemical method for graphitization based on molten salts and an electrodeposition of rare earth elements based on ionic liquids, which require significantly reduced processing temperatures, will be presented. These electrochemical processes have great potential to reduce energy costs compared to existing processes.
Differentiating the Structure and Dynamics of Solute-Bound Vs. Bulk Water in Deep-Eutectic Aqueous AlCl3 Solutions
Authors: Shipman Angela Marie , Martin James D
Published: November 2022

Aqueous solutions of aluminum chloride exhibit a deep eutectic (-52˚C) that is likely due to solute-directed formation of complex network structures in the solvent. It is well known that the solute-bound solvent must have a distinct chemical environment from that of the bulk solvent. Commonly used vibrational spectroscopic measurements of aqueous salt solutions are not selective enough to directly identify distinct water environments in solution. However, variable-temperature 1H-NMR spectroscopy of aqueous solutions, specifically those with high charge density salts, can distinguish water directly bound to the cation from water of the bulk solution. This unique ability to resolve characteristic water peaks by NMR spectroscopy affords the opportunity to explore the hydration structure and dynamics of deep-eutectic aqueous solutions. The aqueous AlCl3 system is an excellent model to study solution structure since we can exploit the high charge density of the ions for which strong ion-dipole interactions are structure-directing to the solvent waters, allowing resolution of distinct water chemical environments. We conducted a thorough investigation of the composition- and temperature-dependent solution structure of the AlCl3 : water system using 1H-NMR spectroscopy, and X-ray and neutron diffraction. The room-temperature proton chemical shift of water proceeds downfield with increasing salt concentration until AlCl3•22H2O, the eutectic composition, after which further increasing concentration results in an upfield chemical shift (see Figure.) Using VT-NMR, we can resolve the first-nearest neighbor water signals from the bulk signal upon cooling. 1H-NMR T1 and T2 relaxation measurement of the distinct water environments reveal stark differences in proton mobility for compositions on the water-rich versus AlCl3-rich sides of the eutectic, implying significant changes in hydration structure. To evaluate the extent to which these changes are structural, a parallel set of composition- and temperature-dependent neutron and X-ray diffraction experiments demonstrate that both cations and anions exhibit significant structure-directing influences on the solution, which we hypothesize underlies deep eutectic behavior in aqueous solutions.

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To Freeze or Not to Freeze: Questioning the Origin of the Deep Eutectic in the Zinc Chloride Hydrate System
Authors: Martin James D , Boyd Shelby
Published: November 2022

Zinc chloride is one of the most soluble salts in aqueous solutions, with an ambient temperature solubility of over 430 g per 100 g of water (ZnCl2·R H2O, R = 1.8). It also exhibits a deep eutectic, at R = 7.25 and -60 °C between pure water and the most water-rich crystalline hydrate, R = 4.5 (see Figure). We previously demonstrated that the molecular ions of the crystalline R = 3 hydrate persist into the melt (Tm = 5 °C) resulting in the ionic liquid [Zn(OH2)6][ZnCl4]. Results from an extensive series of Raman spectroscopy and synchrotron diffraction measurements will be shown to demonstrate that the [ZnCl4]2- anion persists to high dilution. These data further provide evidence for a complex hydration structure beyond the first neighbor water of the hexaaquo zinc cation. Notably the complex speciation/hydration structure directly correlates with the concentration-dependent differential scanning calorimetry of this system and will be shown to be the origin of the system’s deep eutectic. Evaluating the concentration dependence of the temperature and heat of the liquidus reveals that this salt solution exists as an ionic liquid up to a concentration of about 98 mole percent water, beyond which it follows more traditional electrolyte descriptions. The principles derived from this structural and spectroscopic analysis can be applied to more generally explain the freezing point depression in diverse systems. In particular, this analysis demonstrates how the phase diagrams and liquidus heat and temperature can reveal the nature of speciation within aqueous salt solutions.

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Deferred-Action Lithium-Based Batteries
Authors: Liu Danny , Garich Holly , Snyder Stephen , More Santosh R , Hall Timothy , Inman Maria , Taylor E. Jennings
Published: November 2022

Deferred-action batteries, also known as reserve batteries, fulfill a unique role among energy storage technologies in which long-term shelf life (years, decades) is required while ensuring optimal performance upon activation. This objective is typically achieved through isolation of the electroactive components until battery operation is desired. Commonly, the electrolyte is isolated from one or both electrodes, and thus, limiting premature degradation and parasitic side-reactions until battery power is needed. During the reserve battery activation process, electrolyte is delivered to the electrode(s), which enable ionic conduction between the anode and cathode, and thus permitting normal operations analogous to a non-reserve design – which is ubiquitous among off-the-shelf batteries.

The feasible activation mechanisms are largely determined by battery chemistries and material properties, which give rise to several classifications including: thermal, spin-activated, and gas-activated reserve type batteries. Reserve battery activation under these various classifications require ancillary components and specific conditions which contribute excess complexity, weight, and volume towards the overall battery design and thus, significant penalties in reliability, specific and volumetric densities are incurred. Improvements in reserve battery technology must include strategies for limiting these penalties through innovated electrolyte delivery designs tailored for modern, high-energy, high-power density lithium-based batteries.

Herein, we report a novel electrolyte delivery mechanism facilitated by an electrochemical aperture. The electrochemical aperture serves as a physical barrier, isolating the liquid, lithium-containing electrolyte. Reserve battery activation proceeds via lithium transport, inducing physical transformations via the electrochemical aperture, which permit liquid electrolyte injection into the appropriate compartment(s). Accordingly, ionic conduction between the anode and cathode is established, and ultimately resulting in battery activation and enabling typical battery operation. Strategies for quantifying and reducing activation time via material optimization will be explored.

Acknowledgements: Faraday Technology acknowledges the technical assistance of Dr. Joseph P. Fellner at the Air Force Research Laboratory, Wright-Patterson AFB (Dayton, OH) under Air Force Contract No. FA8650-19-P2024 (Phase I SBIR) and FA8650-21-C-2300 (Phase II SBIR).

Figure 1
Key Aging Modes and Mechanisms for Extreme Fast Charging of Lithium-Ion Batteries
Authors: Tanim Tanvir R. , Yang Zhenzhen , Finegan Donal P. , Colclasure Andrew M. , Dufek Eric J. , Bloom Ira , Weddle Peter J , Evans Michael , Smith Kandler , Jansen Andrew N.
Published: November 2022

Enabling extreme fast charging (XFC, charging in 10 to 15 minutes) in a lithium-ion battery (LiB) could play a key role in subsiding consumer’s range anxiety and spur the widespread adoption of electric vehicles (EVs).1,2 Such a high rate of charging induces unique aging modes in LiBs, thereby requiring a comprehensive understanding to enable effective solution strategies to minimize the negative effects of life and performance. This presentation will present a comprehensive understanding of the dominating aging modes and mechanisms of XFC in low- and moderate-loading Gr/NMC LiBs.

We will discuss the major limitations of XFC in LiBs by first using experimental and modeling results followed by a comprehensive electrochemical analysis of cycle life aging implications for different charging conditions (e.g., 1C to 9C rate conditions). We will then discuss the aging mechanisms using comprehensive post-testing as well as multimodal and multi-scale microscopy techniques.

Solid state diffusion in the negative electrode is not a key limiting factor for the fast charge conditions evaluated. Inadequate Li+ transport through the electrolyte primarily causes performance and distinct aging phenomena in LiBs. Eliminating the Li+ transport limitation within the electrolyte can offer a distinct increase in material utilization, avoiding Li deposition. Under such circumstances, the cathode could degrade in distinct ways depending on the particular NMC (e.g., NMC532 vs. NMC811) variants.

NMC811 experiences a greater subsurface crystallographic degradation and interfacial degradation and displays similar extents of sub-particle cracking as compared to NMC532 under comparable charging conditions. Surprisingly, the NMC811 maintains superior electrochemical performance despite the more aggressive degradations. We found the better cycle life performance of NMC811 to be related to its inherently better solid state diffusion, electronic conduction, and radially oriented grain architecture.

References

S. Ahmed et al., J. Power Sources, 367, 250–262 (2017).

Y. Liu, Y. Zhu, and Y. Cui, Nat. Energy, 4, 540–550 (2019).
Designing Ether-Based Electrolytes for Stable Lithium Metal Cycling at Low Temperatures
Authors: Yoon Sun Geun , McDowell Matthew T
Published: November 2022

The lithium metal anode is important for battery applications because of its promising electrochemical properties. However, its poor performance at low temperatures (below -20 °C) is one of the most challenging issues for practical battery applications. Herein, we designed a new ether-based electrolyte for improved lithium metal anode cycling at low temperature conditions and investigated its solvation behavior and the nature of the solid-electrolyte interphase (SEI). We combined the binary solvents 1,3-dioxolane (DOL) and 1,1,2,2-tetrafluoroethyl 2,2,2-trifluoroethyl ether (TTE), along with a fluoroethylene carbonate (FEC) additive, to achieve high Coulombic efficiency (CE) at low temperature conditions (CE = 91.4% and 86.3% at -40 °C and -50 °C, respectively). Based on X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis, we found that TTE increased the interfacial decomposition of FEC and the counter-anion bis(trifluoromethane)sulfonimide (TFSI-), thereby helping to form a stable SEI layer for low temperature lithium cycling. Our findings provide engineering strategies for tailoring the SEI layer and desolvation energetics to enable more highly reversible Li electrodeposition at low temperature, and they are an advance toward improved operation of Li batteries at low temperatures.