bluuebunny/crossref_metadata_2025_split huggingface dataset:
Operando Mössbauer Spectroscopy Investigations of Li-Ion Batteries and Non-Precious Metal Electrocatalysts for PEM Fuel Cells
Authors: Sougrati Michel , Jumas Jean-Claude , Stievano Lorenzo 
Published: February 2020

In the last decade, a growing number of Mössbauer spectroscopy papers dealing with Li-ion batteries and non-precious metal catalysts have been published.[1] As for other Material Science branches, this technique is first used in each of the steps leading to the synthesis of innovative materials. Moreover, Mössbauer spectroscopy is almost routinely used for ex situ and in situ investigations of the electrochemical behavior of electrode materials containing the common Mössbauer isotopes 121Sb[2]
119Sn[3] and more frequently 57Fe[4].
In this presentation, we will see how Mössbauer spectroscopy has became indispensable for optimizing the synthesis routes as well as the performances of functional materials. Through examples from our group and other published work, we will illustrate the importance of this technique for batteries study.
Many iron and tin compounds will be presented (LiFe1-xMnxSO4F, LiFe1-xMnxPO4, TiSnSb etc). Among them, the newest cathode material LiFeSO4F can be given as a pedagogic example showing the role that can be played by Mössbauer spectroscopy in the preparation of this phase, its characterization, and the fabrication of polymeric electrode[5].
Finally, application of Mössbauer spectroscopy to heat-treated transition iron-NxCy electrocatalysts for O2 reduction in acid PEM Fuel cells will be presented [6].
References:
[1] (a) J. C. Jumas and P. E. Lippens, Mössbauer Effect Reference and Data Journal 2010, 33., (b) 1. Jaouen, F.. In Non-Noble Metal Fuel Cell Catalysts, Wiley-VCH Verlag GmbH & Co. KGaA: 2014; pp 29-118.
[2] C. Villevieille, C. M. Ionica-Bousquet, J. C. Jumas, and L. Monconduit, Hyperfine Interactions 2008, 187, 71.
[3] F. Robert, P. E. Lippens, J. Olivier-Fourcade, J. C. Jumas, F. Gillot, M. Morcrette, and J. M. Tarascon, Journal of Solid State Chemistry 2010, 180, 339.
[4] Ou Mao, R. A. Dunlap, I. A. Courtney, and J. R. Dahn, Journal of The Electrochemical Society 1998, 145, 4195.
[5] M. Ati, Moulay T. Sougrati, N. Recham, P. Barpanda, J. B. Leriche, M. Courty, M. Armand, J. C. Jumas, and J. M. Tarascon, Journal of The Electrochemical Society 2010, 157, A1007.
[6] A. Zitolo, V. Goellner, V Armel, M. T. Sougrati, T. Mineva, L. Stievano, E. Fonda, F. Jaouen. Nat Mater 2015, 14, 937.
Quantitative Life Prediction Using High Precision Coulometry with Automotive Current Rates
Authors: Marcicki James , Masias Alvaro , Coupar Thomas , Elsayed Omar 
Published: February 2020

The experimental verification of a Lithium-ion battery for automotive life requirements utilizes significant laboratory resources and calendar time. If the amount of life testing required to validate a cell design for automotive applications can be reduced, new cell designs could be confidently implemented at lower cost and in shorter time. High precision coulometry (HPC) has recently emerged as a promising candidate for shortening the time required for validating cell life. Literature examples have demonstrated improved identification of the mechanisms causing capacity fade1 and qualitative sorting of higher performing cells2.
Academic groups have pioneered this approach but have been primarily limited to testing low currents that are used to probe the rates of side reactions in calendar life scenarios. Our research focus has been the design, development and validation of a 200 A, high precision (<50 ppm current and <25 ppm voltage) battery tester in partnership with Arbin Instruments and Sandia National Laboratory, with the support of the US Department of Energy (DOE) Advanced Research Projects Agency- Energy (ARPA-E)3. The capability to perform high precision measurements at currents up to 200 A means the additional degradation brought about by high-rate cycling can be evaluated in addition to calendar assessments. Additionally, we aim to quantitatively assess performance degradation trends by linking presently measured values to future performance.
Validation testing is presented using 5 Ah prismatic cells to quantify the reduction in test time that is practically achievable using high precision measurements. Continuous cycle aging using multiple current profiles and ambient temperatures is conducted with periodic reference performance tests. The mathematical relations between capacity, resistance, coulombic efficiency, and electrode endpoint slippage are leveraged to define various life prediction methods. The reference performance test measurements from both the high precision tester and standard commercial reference tester are entered as inputs into the life prediction models. Improved measurement precision can result in reduced uncertainty bands when extrapolating life metric trends into the latter stages of cell life. Enhanced measurement precision can also enable the quantification of long term trends at earlier stages of testing.
References:

A.J. Smith, J.C. Burns, D. Xiong, and J.R. Dahn, J. Electrochem. Soc., 158 (10), A1136 – A1142 (2011).

J.C. Burns, A. Kassam, N.N. Sinha, L.E. Downie, L. Solnickova, B.M. Way, and J.R. Dahn, J. Electrochem. Soc., 160 (9), A1451 – A1456 (2013).

A. Masias, The Bridge – National Academy of Engineering. 45 (1), 13 – 20 (2015).
Developing High Cycling Stability Graphite/LiNi0.5Mn1.5O4 Li-Ion Cells
Authors: Gabrielli Giulio , Axmann Peter , Wohlfahrt-Mehrens Margret 
Published: February 2020

Key issues for the next generation of Li-Ion batteries are increasing the specific energy and reducing the cell cost. It is possible to achieve both this targets by adopting innovative and cheap cathode materials presenting either higher capacity or higher operating potential than standard cathode materials. Among the high voltage materials, LiNi0.5Mn1.5O4 (LMNO) is one of the most promising candidates for Li-Ion cells application because of its operating potential of 4.7 V vs. Li/Li+, its good specific capacity (147 mAh g-1) and low cost. Graphite/LMNO cells guarantee considerable improvements in the specific energy of Li-Ion batteries by increasing the cell operating voltage to ca. 4.6 V. Unfortunately Graphite/LMNO systems undergo a strong aging process and a rapid capacity fade because of the electrolyte degradation reactions occurring at high potential. Thus, it is necessary to adopt different strategies such as the optimization of the active material, the adoption of coatings and the optimization of the electrolyte in order to stabilize the cathode/electrolyte interface. Adopting these strategies, it was possible to significantly increase the cycling life of Graphite/LMNO cells up to more than 700 cycles (Figure).
The development of stable Graphite/LMNO cells starts with the optimization of the cathode active material. Thus, we studied and tailored morphological properties of LMNO such as particle architecture, composition, crystallite size and particle size. This study aimed to realize an optimized LMNO, presenting features in line with commercial cathode materials and the best compromise between electrochemical performance and reduced electrolyte degradation. The optimized LMNO in full-cells vs. graphite anodes showed remarkable electrochemical performance and a stable reversible capacity for more than 300 cycles.
Additional strategies for improving the cycling life of Graphite/LMNO cells included a facile oxidic treatment of the LMNO particles surface. The aim of this treatment was to further stabilize the cathode/electrolyte interface without altering the electrochemical performance of the active material. Moreover, we pointed out the importance of using a suitable electrolyte composition, which guarantees high voltage stability without interfering with the performances of the full-cells. Electrochemical studies in full-cells showed a significant contribution of these improvements to the cycling stability of Graphite/LMNO cells and the validity of the adopted strategies.

Figure 1
Selenides Based Sodium Superionic Conductors
Authors: Bo Shou-Hang , Wang Yan Eric , Kim Jae Chul , Richards William Davidson , Ceder Gerbrand 
Published: February 2020

All-solid-state Na-ion batteries that operate at or close to room temperature are a promising next-generation battery technology with enhanced safety and reduced manufacturing cost. An indispensable component of this technology is the solid state electrolyte that allows rapid shuttling of the mobile cation (i.e., Na+) between the cathode and anode. However, there are very few fast Na-ion conductors with ionic conductivity approaching that of the liquid counterparts (i.e., 1 mS cm-1).
Compared to oxides and sulfides, selenides form a huge unexplored chemical space for fast ionic conductor discovery. Based upon ionic size considerations, selenide-based compounds may provide a more suitable structural framework for the rapid diffusion of the much larger Na+ cations compared with Li+. This consideration led us to an extensive search of fast Na-ion conductors in the Se-based chemical space via high-throughput computational screening, and has identified cubic Na3PSe4 as one of the most promising candidates.
In this work, we present the synthesis and structural characterization of Na3PSxSe4-x (x = 0, 1, 2, 3, 4). The structures of these phases are determined from high-resolution synchrotron X-ray diffraction data, which allow us to unambiguously identify a tetragonal-to-cubic phase transition with increasing Se concentration in Na3PSxSe4-x. The Na-ion conductivity and activation energy for Na-ion diffusion were further characterized via variable temperature impedance spectroscopy, from which a negative correlation between the activation barrier and Se concentration can be established. Of particular note is that the x = 4 end member (i.e., cubic Na3PSe4) possesses a room-temperature ionic conductivity exceeding 0.1 mS cm-1, and does not require high temperature sintering to minimize grain boundary resistance, making it a promising solid-state electrolyte candidate for all-solid-state Na-ion battery applications. These experimental results were complemented by ab initio computation through which we demonstrate an intriguing interplay between the tetragonal-to-cubic phase transition, defect formation, and Na+ migration.
This work has two important implications for future studies in related fields: (1) selenide based compounds represent a promising platform for the discovery of new fast Na-ion conductors; and (2) the current study opens up new opportunities for the exploration of Se and/or S based battery chemistry, such as the construction of all-solid-state Na/Se battery.
X-Ray Nanotomography of Cu6Sn5 Anode Material for Li-Ion Batteries
Authors: Ausderau Logan , Buckley Joseph , De Andrade Vincent , Nelson George J. 
Published: February 2020

In recent years, great attention has been paid to tin as an alternative to graphite as a negative electrode material in Li-ion batteries due to the high theoretical capacity of its fully lithiated phase, Li4.4Sn (994 mAh∙g-1). However, tin suffers from large volume expansion during lithiation and delithiation causing capacity to drop quickly as a function of cycle number. Significant volume expansion of the negative electrode has severe effects that reduce the cycle lifetime of the electrode such as material pulverization, separation from the current collector, and instability of the solid electrolyte interphase. One way to reduce this expansion is to create an inert matrix to help support the Sn during electrochemical cycling such as the use of copper in the form of the intermetallic alloy Cu6Sn5.
As the issues stemming from this severe volume expansion all occur on a microstructural level, x-ray nanotomography (XNT) is used to image the anode material at a resolution of 60 nm. XNT provides the opportunity to non-destructively obtain the 3D structure of heterogeneous materials and provide a series of high resolution digital images for microstructural analysis and computational modeling. In this current study, Cu6Sn5 was synthesized by sintering copper and tin in the stoichiometric proportion to form the alloy anode material. XNT measurements were taken of the resulting non-lithiated material at 8.8 KeV over a 180° range of rotation. Single component and mixed samples containing the bronze alloy, Cu, and Sn were imaged. Based on absorption contrast regions of Cu, Sn, and Cu6Sn5 were differentiated throughout multiple samples. The capability to distinguish the different materials within mixed samples suggests that microstructure and composition changes resulting from lithiation and delithiation in Cu6Sn5 can be observed and better understood with 3D x-ray imaging methods. These methods may also be applicable to other intermetallic alloy electrode systems.
(Invited) Synthesis of Nitrogen-Embedded Buckybowl and Its Strong Association Behavior with C60
Authors: Hiroto Satoru , Yokoi Hiroki , Sakamaki Daisuke , Seki Shu , Shinokubo Hiroshi 
Published: February 2020

Curved π-conjugated molecules have attracted considerable interest because of their unique properties originating from their curved π surface. Besides their figurative beauty, the curved psurface generates unique functions such as chiroptical properties, anisotropic electron transitions, and dynamic motion in solution and solid states. However, the synthesis of such distorted molecules requires harsh conditions, which hamper an easy access to heteroatom-containing curved π-systems.
Buckybowls represent important curved π-conjugated molecules, which can be precursors for the bottom-up synthesis of fullerenes and nanotubes. The nitrogen-embedded bowl-shaped molecules have been sought as model compounds for azafullerenes and nitrogen-doped carbon nanotubes. However, the synthesis of buckybowls with internal nitrogen atoms has been still challenging.
Here we report the synthesis of a π-extended azacorannulene with nitrogen in its center. The oxidation of 9-aminophenanthrene provides tetrabenzocarbazole, which is converted to the azabuckybowl through palladium-catalyzed intramolecular coupling reaction. The structure was unambiguously elucidated by X-ray diffraction analysis, showing its bowl-shaped conformation. The electron-donating nature and curved π surface of the azabuckybowl enable its tight association with C60 in solution and solid states. The titration experiments with C60 by electronic absorption and emission spectroscopic analysis indicate the presence of intermolecular charge-transfer interaction between them. In addition, high charge carrier mobility was observed for the azabuckybowl/C60 assembly in solid state. This new compound would be a novel molecular entity in the field of curved π systems as fullerene hosts, anisotropic π donors, and precursors to nitrogen-containing nanocarbon materials.

Figure 1
(Invited) Synthesis of Fluorescent Graphene Quantum Dots
Authors: Haino Takeharu 
Published: February 2020

A Graphene quantum dots have received great attention for a potential role in the development of unique optoelectronic materials. In the development of optoelectronic devices, the preparation of GQDs that are controlled with their size and dimensions and are un-oxidized at the sp2 surfaces is needed. We developed GQDs functionalized with bulky dendritic wedges at the GQD periphery. The single-layered and size-regulated structures of the dendronized GQDs were revealed by atomic force microscopy. The edge-functionalization of the GQDs gave rise to uncommon white light emission.
In this presentation, I will describe the synthesis and characterization of newly developed graphene quantum dots, and the unique photochemical features.
1) Sekiya, R.; Uemura, Y.; Murakami, H.; Haino, T. Angew. Chem. Int. Ed.
2014, 53, 5619-5623.

Figure 1
(Invited) Photoinduced Charge Transfer Reactions and Excited State Properties in Triphenylamine C60 Donor-Acceptor Conjugates
Authors: Solà Miquel , Martínez Juan Pablo , Osuna Sílvia , Voityuk Alexander 
Published: February 2020

The molecular heterojunction triphenylamine/C60 is a potential material to construct high-efficient dye-sensitized solar cells. We have carried out a combined molecular dynamics and time-dependent density functional theory study to analyze charge separation and exciton delocalization in excited states of two constitutional isomers of this interface.[1] Our results reveal the presence of exciton states characterized by partial charge-transfer character (hybrid states); which are suggested to promote the direct charge separation process by excitation. These states may have a significant impact on the efficiency of the light-harvesting ensembles. That is to say, a greater amount of such hybrid states is found at short distances between the triphenylamine fragment and the C60 cage; as a result, charge transfer reactions can occur faster. This trend resembles the experimental evidence since rate constants for photoinduced charge transfer reactions kct
are bigger for the constitutional isomer with the shortest distance between the triphenylamine fragment and the C60 cage.[2] We have also evaluated the performance of U-CAM-B3LYP/6-31G* and TD-CAM-B3LYP/6-31G* level of theories to compute the different parameters affecting kct
; that is the reorganization energy λ, the electronic coupling Vij
, and free energies ΔG.[3] Our study is done under the theory of nonadiabatic electron transfer. By using the standard Marcus formulation, our results show that the outer-sphere contribution to λ and ΔG for the recombination reaction are the parameters that more uncertainty introduces to the estimation of kct
. We implemented a low-cost methodology based on U-DFT for the evaluation of the outer-sphere part of λ and ΔG; wherein Franck-Condon and relaxed charge-transfer states are conveniently modeled, including properly the solvent reorganization energy, by U-CAM-B3LYP/6-31G* coupled to continuum solvation models. Finally, it is worth to mention that the replacement of the C60 cage by Ih
-Sc3N@C80 generates longer-lived charge-transfer states; which is attributed to the lower ΔG of the charge recombination reaction.[2] Our group is currently analyzing this trend for the whole family of endohedral metallofullerenes; for which dynamics is expected to be in the normal region of the Marcus parabola.
[1] J. P. Martínez, S. Osuna, M. Solà, A. Voityuk, Theor. Chem. Acc.
2015, 134, 12.
[2] J. R. Pinzón, D. C. Gasca, S. G. Sankaranarayanan, G. Bottari, T. Torres, D. M. Guldi, L. Echegoyen, J. Am.
Chem. Soc.
2009, 131, 7727–7734.
[3] J. P. Martínez, M. Solà, A. Voityuk, 2015, in preparation.

Figure 1
(Invited) Fullerene-Based Multichromophoric Antennas
Authors: Bonifazi Davide 
Published: February 2020

Based on the unique electronic and structural properties, carbon nanostructures and are promising candidates for the constructions of advanced multidimensional organic architectures. Therefore a detailed understanding of the chemical and physical properties of these all-carbon structures is crucial for the further and targeted development of advanced materials. The main purpose of our work is to design and investigate new classes of carbon nanostructures with defined structural, physical, and chemical properties which are suitable as functional materials, e.g. in the field of organic conductors, photonic applications, and biological applications.
Herein we report the recent progresses achieved in our laboratory on the synthesis, characterization, and physical studies of new classes of [60]fullerene-based reaction centers equipped with new chromophoric antennas.
(Invited) Carbon Nanotubes-Fullerene Hybrids
Authors: Langa Fernando , Gomez-Escalonilla María J. , Barrejon Myriam 
Published: February 2020

The combination of two carbon nanostructures in a single material, giving rise to new hybrids with improved mechanical, electrical, and thermal properties, has sparked a great interest in the last years.[1],[2],[3] Hybrids combining carbon nanotubes and fullerene derivatives have been described by endohedral,[4] supramolecular[5] and covalent[1] approaches, showing, in general, rather poor solubility in common solvents, which hampered the study of the resulting photophysical properties. In this regard, the synthesis of nanohybrids bearing long alkyl chains,[2]
,
[6]improve the dispersibility in organic solvents, rendering them excellent candidates for their application in the semiconducting materials field.
In this presentation, we will discuss our recent studies involving the synthesis of nanohybrids combining carbon nanotubes and C60, as well as the new photophysical properties arising from the combination of both carbon nanomaterials.

[1] J. L. Delgado, P. de la Cruz, A. Urbina, J. T. López Navarrete, J. Casado and F. Langa, Carbon, 2007, 45, 2250.
[2] M. Vizuete, M. J. Gómez-Escalonilla, J. L. G. Fierro, M. Yudasaka, S. Iijima, M. Vartanian, J. Iehl, J.-F. Nierengarten and F. Langa, Chem.
Commun., 2011, 47, 12771.
[3] M. Vizuete, M. Barrejón, M. J. Gómez-Escalonilla and F. Langa, Nanoscale, 2012, 4, 4370.
[4] B. W. Smith, M. Monthioux and D. E. Luzzi, Nature,
1998
, 396, 323.
[5] D. M. Guldi, E. Menna, M. Maggini, M. Marcaccio, D. Paolucci, F. Paolucci, S. Campidelli, M. Prato, G. M. A. Rahman and S. Schergna, Chem. Eur. J.
2006, 12, 3975.
[6] N. Mackiewicz, T. Bark, B. Cao, J. A. Delaire, D. Riehl, W. L. Ling, S. Foillard and E. Doris, Carbon, 2011, 49, 3998.
(Invited) New Photocurrent Generating Pathways in Twisted Bilayer Graphene and Stacked Transition Metal Dichalcogenide Materials
Authors: Graham Matt W 
Published: February 2020

The high-conductivity, low cost and relative ease of fabrication have made graphene well-suited to transform nanoscale electronics. Unfortunately, as a gapless semimetal, photo-excited electrons in graphene recombine far faster than electron-hole pairs can be extracted.[1] To make carrier lifetimes in 2D materials more competitive with carrier separation, we demonstrate promising, new electron extraction pathways in graphene-like systems including twisted bilayer graphene (tBLG) and transition metal dichalcogenides (TMD). In tBLG, we show the emergence of twist angle-tunable excitonic absorption peaks that result from the rehybridization of constrained interlayer 2p orbitals[2]. Specifically, we use one and two-photon transient absorption microscopy to directly image the predicted[3] bright and dark stable, strongly-bound excitons states. This observation of strongly bound excitons is a first for a 2D metallic system, and serves to substantially increase graphene’s carrier lifetime, suggesting new pathways for photocurrent collection. Unlike graphene, semiconducting 2D TMDs like WSe2, have long carrier lifetimes, but challenging mobility and exciton dissociation bottlenecks that inhibit photocurrent generation. By combining femtosecond resolved photocurrent microscopy[1,4] with ultrafast transient absorption, we have selectively imaged the dominant kinetics bottlenecks that inhibit photocurrent production in devices made from WSe2TMD materials. Using these ultrafast space-time maps of the electron-hole dissociation dynamics, we hope to better engineer 2D material heterostructures devices to avoid efficiency-destroying, carrier recombination bottlenecks and maximize photocurrent yield.
(1) M.W. Graham, S. Shi, D.C. Ralph, J. Park, P.L. McEuen (2013), Nature Physics, 9, 103
(2) H. Patel, R. Havener, L. Brown, Y. Liang, L. Yang, J. Park, M.W. Graham (2015), Nano Letters, 15, 5932-7
(3) Y. Liang, R. Soklaski, S. Huang, M.W. Graham, R. Havener, J. Park, L. Yang (2014), Phys Rev B, 90, 115418
(4) M. Massicotte, P. Schmidt, F. Vialla, K. G. Schädler, A. Reserbat-Plantey, K. Watanabe, T. Taniguchi, K.-J. Tielrooij, and F. H. L. Koppens (2015), arXiv:1507.06251 [cond-mat]