bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Excited State Processes in Semiconductor Nanocrystals and Their Relationships with Light-Driven Multi-Electron Catalysis
Authors: Dukovic Gordana
Published: February 2020

This presentation will focus on the excited state behavior of semiconductor nanocrystals as light absorbers that, coupled with redox catalysts, drive light-driven multi-electron transfer reactions. Reactions of interest include hydrogen generation, carbon dioxide reduction, nitrogen fixation, and water oxidation. We have demonstrated that nanocrystal excited state behavior, charge transfer dynamics, and surface chemistry play a governing role in the overall photochemistry of nanocrystal-catalyst complexes. This presentation will describe our most recent findings about how the reactions of interest can be driven and controlled through manipulation of nanocrystal excited state dynamics. In particular, the presentation will focus on: (i) measurement (by transient absorption spectroscopy), kinetic modeling, and control of electron transfer kinetics for injection of photoexcited electrons into redox enzymes; and (ii) elucidation of the motion of photoexcited holes on nanocrystal surfaces, using a combination of transient absorption measurements, modeling, and theory, and the implications of this motion on oxidation photochemistry.
(Invited) Atomic View of Nickle Dithiolene Electro- and Photo-Catalysis Using X-Ray Absorption Spectroscopy
Authors: Cordones-Hahn Amy
Published: February 2020

Metal dithiolenes are a class of molecular catalysts known for their redox-active ligands and their efficient and robust electro- and photo-catalysis of the hydrogen evolution reaction. To understand how the redox-active ligands of these catalysts participate in their chemical reactions, we need atom-specific probes of charge and bonding at both metal and ligand atomic sites. X-ray absorption spectroscopy (XAS) affords us this opportunity and is used to study the electro- and photo-catalytic reaction mechanisms of these complexes, with a specific focus on the role of metal versus ligand atomic sites. Static soft x-ray XAS studies of Nickle dithiolene catalysts at the Ni L-edge and S K-edge will be presented to resolve the electronic structure of these complexes. Static and transient XAS of Nickle aminothiolate complexes at the Ni K-edge will be presented to resolve their electro- and photo-catalytic reaction mechanisms. These results highlight the unique ability of x-ray spectroscopy to clarify the role of redox-active ligands during catalysis.
High-Entropy Transition Metal Dichalcogenides As Exceptional Electrocatalysts of Hydrogen Evolution Reaction (HER)
Authors: Lan Tian , Hlova Ihor , Pecharsky Vitalij , Pathak Arjun , Balema Viktor , Padalkar Sonal
Published: February 2020

Hydrogen is a unique energy carrier in that it can be produced via diverse pathways utilizing a variety of available feedstocks, including natural gas, biomass, and water. Electrolysis of water is among the most versatile methods of hydrogen generation that currently play a significant role in hydrogen gas production [1]. Among different water splitting technologies, low temperature electrolysis emerges as superior contender, demonstrating high current density (2 Am-2), low working temperature (82 oC) and operation under high pressures of H2 (~200 bar) [2]. However, one of its main weaknesses is the high cost and scarcity of platinum (Pt), which is an essential element of conventional electrolytic systems. Hence, the development of novel, efficient Pt-free electrocatalysts for hydrogen evolution reaction (HER) belongs to the major objectives of the water splitting materials research.

This talk highlights a new family of high-entropy materials – multi-principal element transition metal dichalcogenides (HE-TMDCs) – that show exceptional electrocatalytic activity approaching the water-splitting activity of platinum in HER. Novel HE-TMDCs, developed with support from Ames Laboratory’s LDRD funding, are single-phase, layered materials, which are built from several different 3d – 5d metals (M = Mo, W, Nb, Ta etc.) and chalcogens (X=S, Se), e.g. (M,M’,M’)(X,X’) [3]. Their electrochemical performance will be presented, and compared with those of conventional binary TMDCs, and Pt. Electrode preparation techniques, the electrochemical measurements and possible reasons for the exceptional performance of the HE-TMDCs electrodes will be discussed.

References

1. https://www.energy.gov/eere/articles/hydrogen-clean-flexible-energy-carrier

2. Schmidt, O. et al. Int. J. Hydr. Energy,
42, 30470 (2017)Hlova, I.Z. et al. Chem. Commun.
54, 12574 (2018)

3. Hlova, I.Z. et al. Chem. Commun.
54, 12574 (2018)
(Invited) Hole Extraction Layer Boosting Photoelectrochemical Solar Water Splitting
Authors: Park Jong Hyeok , Zhang Jong
Published: February 2020

As the development of oxygen evolution co-catalysts (OECs) is being actively undertaken, the tailored integration of those OECs with photoanodes is expected to be a plausible avenue for achieving highly efficient solar-assisted water splitting. Here, we demonstrate that a black phosphorene (BP) layer, inserted between the OEC and BiVO4 can improve the photoelectrochemical performance of pre-optimized OEC/BiVO4 (OEC: NiOOH, MnOx, and CoOOH) systems by 1.2~1.6-fold, while the OEC overlayer, in turn, can suppress BP self-oxidation to achieve a high durability. A photocurrent density of 4.48 mA·cm-2 at 1.23 V vs reversible hydrogen electrode (RHE) is achieved by the NiOOH/BP/BiVO4 photoanode. It is found that the intrinsic p-type BP can boost hole extraction from BiVO4 and prolong holes trapping lifetime on BiVO4 surface. This work sheds light on the design of BP-based devices for application in solar to fuel conversion, and also suggests a promising nexus between semiconductor and electrocatalyst.
(Invited) High-Rate Solar-Light Photoconversion of CO2 to Fuel: Synthesis and Characterization
Authors: In Suil
Published: February 2020

The production of solar fuels oﬀers a viable pathway for reducing atmospheric CO2 concentrations and the storage and transport of solar energy. While photoconversion of CO2 into C1 hydrocarbon products, notably methane (CH4), is known, the ability to directly achieve significant quantities of higher-order hydrocarbons represents an important step towards practical implementation of solar fuel technologies. We describe an eﬃcient, stable, and readily synthesized CO2-reduction photocatalyst, Pt-sensitized graphene-wrapped defect-induced blue-coloured titania, that produces a record high combined photocatalytic yield of ethane (C2H6) and methane. For the first time, a systematic ultraviolet photoelectron spectroscopy study on the mechanism underlying ethane formation indicates that the process is dependent upon upward band bending at the reduced blue-titania/graphene interface. Furthermore, transient absorption spectroscopy indicates photogenerated holes move into the graphene while electrons accumulate on the Ti3+ sites, a phenomenon contradicting prior assumptions that graphene acts as an electron extractor. We find that both mechanisms serve to enhance multielectron transfer processes that generate ·CH3. Utilizing a continuous flow-through (CO2,H 2O) photoreactor, over the course of multiple 7 h runs approximate totals of 77 mmol g-1 C2H6 and 259 mmol g-1 CH4 are obtained under one sun AM 1.5G illumination. The photocatalyst exhibits an apparent quantum yield of 7.9%, 5.2% CH4 and 2.7% C2H6, and stable photocatalytic performance over the test duration of 42 h. The carbon source for both products is verified using 13CO2 isotopic experiments.
Evaluating Photoelectrochemical Redox Processes for Wastewater Nitrate Removal Coupled with Energy and Nutrient Recovery
Authors: Barrera Luisa , Bala Chandran Rohini
Published: February 2020

Excessive anthropogenic production of nitrogen fertilizers combined with rapid industrialization has disrupted the natural balance of the nitrogen cycle leading to increased concentrations of reactive-nitrogen/nutrient species including nitrates (NO3
-), nitrites (NO2
-), and ammonium (NH4
+) in groundwater, rivers and lakes1,2. These nutrient imbalances can lead to health risks to human beings by causing methemoglobinemia in infants, also known as “blue baby syndrome,” and may cause cancer in adults, and negatively impact the environment by causing acid rain and algal blooms. Despite the chemical energy that is stored in common dissolved contaminants in water, wastewater treatment poses the challenge of being a highly energy intensive process. In this study we propose a photoelectrochemical approach (see figure below) to oxidize water and reduce nitrates (NO3
-) to various nitrogen-species including N2, and other value-added products such as NH3 and N2O. NH3 can be directly used as a fuel and/or for fertilizer production, and N2O is a powerful oxidant in combustion reactions (used as “nitrox” to supercharge engines of high performance vehicles); in the combustion of methane (CH4), N2O increases the heat released in the reaction by 37% as compared to when O2 is used as an oxidant.

Thermodynamic analyses is first performed to predict the solar energy conversion efficiencies for the various product species. Thermodynamic predictions show that N2O could be a more promising value-added NO3
- reduction product compared to NH3 due to the increased aqueous solubility of the latter, which leads to significant dissolved gas crossover losses. Furthermore, a coupled species transport and reaction kinetics model is developed to predict overall rates of product formation for tandem photoelectrochemical reactor designs. Specifically, the model developed is applied to quantify the influences of competing oxidation and reduction reactions and species mass transport on the energy and nutrient recovery potential of the proposed photoelectrochemical device.

References:

Falkowski, P. et al. The Global Carbon Cycle : A Test of Our Knowledge of Earth as a System. Science (80 ).
290, 291–297 (2000).

Duca, M. & Koper, M. T. M. Powering denitrification: the perspectives of electrocatalytic nitrate reduction. Energy Environ. Sci.
5, 9726 (2012).

Figure 1
(Invited) Designing Materials to Revolutionize and Engineer the Future of Clean Energy Technologies through Computationally-Led and Data-Driven Approaches
Authors: Schlueter John
Published: February 2020

The Materials Genome Initiative (MGI) is a multi-agency partnership that seeks to accelerate the pace of materials development across the Materials Development Continuum. Through use of a computationally-led and data-driven approach, MGI promotes the rapid discovery and progression to deployment of advanced materials that will ensure sustained American leadership in sectors including clean energy. The goals of the MGI include 1) leading a culture shift in materials research through use of an iterative feedback-loop approach, 2) integrating experiment, computation, and theory throughout the materials research community, 3) making digital data accessible and useful to the larger community, and 4) creating a world-class materials science and engineering workforce. The Designing Materials to Revolutionize and Engineer our Future (DMREF) program at the National Science Foundation (NSF) partners with a number of other federal agencies to promote these objectives. DMREF currently funds about one hundred projects that cover the full spectrum of materials research, including a number that focus on energy conversion technologies. This talk will provide an overview of the DMREF program and provide specific examples of ways that DMREF teams are benefitting from collaboration with MGI-related efforts at other federal agencies. Interactions with the U.S. Department of Energy's (DOE) Energy Materials Network (EMN) will be highlighted. Future priorities and funding opportunities for the DMREF program will be discussed.
(Invited) Accelerated Discovery for Solar Fuels
Authors: Atwater Harry A , Jaramillo Thomas F. , Houle Frances A , Toma Francesca M. , Gregoire John M. , Weber Adam Z. , Amashukeli Xenia
Published: February 2020

Efficient and selective synthesis of chemical fuels from sunlight, water, and carbon dioxide is a grand challenge for 21st century energy technology. Achieving rapid progress in this area requires accelerated discovery of mechanisms, materials, integration strategies, and device architectures designed for selective catalysis, light capture and conversion, charge transport, and product separation. The current mission of the Joint Center for Artificial Photosynthesis (JCAP) is to accelerate progress in mechanisms, materials, and integrated prototype designs for selective and efficient conversion of carbon dioxide to chemical fuels. In this talk, recent progress accomplished by JCAP will be discussed including discoveries that build upon our previous experience with hydrogen generation via photoelectrochemical water splitting. JCAP's experience with both carbon dioxide reduction and water splitting form a testbed for accelerated discovery, beginning with at the science frontier and culminating in team-oriented development of testbed prototype devices. The structure and achievements of JCAP and related Hub-level research from a materials perspective will be introduced.
(Invited) The U.S. Department of Energy’s HydroGEN Consortium Advances Research for Sustainable Hydrogen Production
Authors: Randolph Katie , Miller Eric L. , Peterson David , Vickers James , Stetson Ned T
Published: February 2020

Dedicated to accelerating the research and development (R&D) of advanced water splitting (AWS) technologies for renewable, low-cost hydrogen production, HydroGEN (https://www.h2awsm.org/) is one of seven of the U.S. Department of Energy’s (DOE) Energy Materials Network (EMN) consortia. HydroGEN comprises six core national laboratories and focuses on four AWS pathways: low- and high-temperature electrolysis, photoelectrochemical, and solar thermochemical water splitting. The consortium provides streamlined access to world-class expertise and experimental and computational capabilities. Current activities span 20 university, industry and national laboratory R&D projects which seek to discover and design new materials, increase the efficiency and durability of water-splitting systems, and advance manufacturing and scale-up efforts. Further, HydroGEN is committed to connecting the AWS research community by developing a data platform for secure data transfers and public data sharing as well as supporting the development of comprehensive best practices and benchmarking methods.
Computational Modeling and Screening of Semiconductor Electrodes for Solar-to-Fuel Conversion
Authors: Dabo Ismaila
Published: February 2020

Solar energy is the most abundant energy source available to humankind, but this energy cannot be harnessed on demand due to the variability of sunlight. Artificial photosynthesis overcomes that variability through the direct photocatalytic storage of solar power into chemical fuels. Nevertheless, most of the stable photocatalysts in use today rely on metal oxide semiconductors whose bandgap does not match the solar spectrum. This presentation will discuss the development and experimental validation of an accurate computational protocol to understand, predict, and optimize visible-light-active materials that can split water into hydrogen and oxygen with a focus on solar compatibility using electronic-structure methods beyond density-functional theory and electrochemical stability by exploiting quantum-continuum embedding methods.

Figure 1
(Invited) Differences in Emission Properties for Triboluminescent EuD4tea Synthesized Using Both Europium Nitrate or Europium Acetate
Authors: Hollerman William A , Fontenot Ross S
Published: February 2020

Europium tetrakis dibenzoylmethide triethylammonium (EuD4TEA) is one of the most intense triboluminescent (TL) materials currently known. Some time ago, the authors reported that the triboluminescent yield was increased by 82% by changing the starting europium salt from europium chloride to europium nitrate. Unfortunately, europium nitrate has been classified as a hazardous material that cannot be shipped by air, which limits the availability of manufacturers and increases the cost. In an effort to further reduce the synthesis cost of EuD4TEA, we explore the effects of europium acetate on the triboluminescent properties of EuD4TEA by comparing the triboluminescent yield. The photoluminescent spectra as well as crystal structure using an optical microscope will also be explored
Electrogenerated Chemiluminescence of Perovskite Quantum Dots
Authors: Yadav Jeetika , Pan Shanlin
Published: February 2020

Metal halide perovskites have attracted immense scientific interest owing to their unique optoelectronic properties, such as high absorption coefficient, band gap tunable in the entire visible range, and high photoluminescence quantum efficiency. Perovskites have been applied to applications in solar cells, photodetectors, nanolasers, and light emitting diodes (LED) because of these unique properties. Light emitting diodes are based on the luminescence of the material. Tunable photoluminescence (PL) and electrogenerated chemiluminescence (ECL) can be obtained from perovskite quantum dots (QDs) by varying their size and shapes because of quantum confinement effect. In this study, ligand assisted precipitation method is used to synthesize lead based mixed chloride and bromide perovskite quantum dots. The absorbance, fluorescence at 450nm, lifetime and quantum yield results will be presented. The average diameter of 3.5±1nm and the d-spacing of 0.3nm was determined using HR-TEM. ECL can be obtained from a transparent electrode coated with perovskite QDs using tripropylamine (TPrA) as the co-reactant in acetonitrile as solvent, although the ECL performance of dry-coated perovskite QDs suffers from decomposition and/or dissolution of the dots into electrolyte. The ECL stability issue can be partially addressed by coating the QDs along with polystyrene film accompanied with decrease in ECL intensity due to the sluggish charge transfer through polystyrene film. A dual ECL peak spectrum with emissions at 480 nm and 580 nm is observed over the period of ECL generation and collection. Further experiments need to be done to fully understand the mechanism behind this shift.
Lu2O3:Mn Ceramics for Thermoluminescence and Thermometry Dual Functionality
Authors: Kulesza Dagmara , Zeler Justyna , Zych Eugeniusz
Published: February 2020

Manganese is capable of exist in many oxidation states from +1 to +7. In research of phosphors especially attractive and intensively studied in last years is a d-d emissions from Mn2+ and Mn4+. In both cases the luminescence may appear in red spectral range, greatly attractive for WLEDs.1 Yet, being strongly dependent on the host lattice the Mn2+ emission can vary from green to deep red with decay time in the order of ms.

This presentation is devoted to Mn2+ emission in cubic Lu2O3 host lattice which offer two nonequivalent site symmetry, C2 and C3i, for the dopant ion.2 A successful technology of effective permanent stabilization of Mn2+ in this host will be presented.

The preliminary spectroscopic investigation showed that the title system is able to produce thermoluminescence after irradiation with X-rays or UV-rays. Furthermore, in PL measurements detected in wide temperature range the system is able to produce 2 or even 3 different emissions whose intensities change in a complex way. These observations tells to consider the possible usefulness of the system to serve as a prospective luminescence thermometer working over a broad range of temperatures.

This research was supported by Polish National Science Centre upon the grant #UMO-2017/25/B/ST5/00824.

Q. Zhou, L. Dolgov, A. M. Srivastava, L. Zhou, Z. Wang, J. Shi, M. D. Dramićanin, M. G. Brik and M. Wu, Mn2+ and Mn4+ red phosphors: Synthesis, luminescence and applications in WLEDs. A review, J. Mater. Chem. C, 2018, 6, 2652–2671.

E. Zych, Concentration Dependence of Energy Transfer between Eu3+ ions occupying two symmetry sites in Lu2O3, J. Phys.
Condens. Matter, 2002, 14, 5637–5650.
Electrochemical Investigations of L-Tryptophan
Authors: Cheek Graham T. , Choi Pyung O.
Published: February 2020

Introduction

Recent activity in this laboratory has involved the electrochemistry of amino acids such as L-cysteine and L-histidine in aqueous buffers (1-4). The effect of zinc ions, which are involved in determining the structures of “zinc finger” proteins (5), on the electrochemistry of amino acids has also been investigated. The present work has extended these studies to L-tryptophan and some of its derivatives.

Experimental

MOPS (3-(N-morpholino)propanesulfonic acid) was obtained from Sigma-Aldrich Corporation, and L-tryptophan was obtained from Nutritional Biochemical Systems. Electrochemical experiments were carried out under nitrogen using a Gamry Instruments Interface 1000 potentiostat and Gamry Framework software. Working electrodes were obtained from BASi (Glassy carbon, 3.0 mm diameter; platinum 1.6 mm) and eDAQ (gold, 1.0 mm diameter). Potentials were measured with respect to a silver/silver chloride saturated KCl reference electrode (eDAQ).

Results and Discussion

Electrochemical studies of L-tryptophan have been carried out in pH 7.4 phosphate buffer, and we have found that L-tryptophan undergoes oxidation more easily than does L-histidine (4). Complexation studies of Zn(II) by L-tryptophan in pH 7.4 MOPS buffer have shown that the extent of complexation is generally similar to that of L-histidine (4). Similar experiments were also carried out on 5-fluoro-tryptophan and 6-fluoro-tryptophan, revealing that they underwent oxidation at somewhat more positive potentials than does L-tryptophan. This observation reflects the electron-withdrawing effect of the fluorine atom. Despite this positive potential shift, the fluorinated tryptophans were found to effectively complex zinc(II) in pH 7.4 MOPS buffer. Finally, initial experiments in the voltammetric behavior of L-tryptophan in the very polar solvent formamide have been initiated.

References

1. G. T. Cheek and M. A. Worosz, ECS Transactions, 2016, 72(27), 1-8.

2. M. Y. Doan, M. A. Worosz, and G.T. Cheek, ECS Transactions, 2017, 77(11), 1537-1544.

3. G. T. Cheek, M. A. Worosz, M. Y. Doan, and D. C. Clark, ECS Transactions 2017 80(10), 1159-1166.

4. D.C. Clark and G.T. Cheek, ECS Transactions, 2018, 85(13), 1123-1131.

5. C.K. Mathews, K.E. Van Holde, D.R. Appling, and S. J. Anthony-Cahill, Biochemistry, 4th Edition, Pearson Canada, Toronto, 2013.
Microelectrode Human Analysis: Circuit Bath Pegged By Reference Potential
Authors: Burgess James D.
Published: February 2020

Microelectrodes allow human in vivo sensing without IR drop uncertainties. The small currents passed permit reliable use of a two-electrode voltage clamp system. The circuit bath is connected directly to a classical true reference electrode. The reference electrode is immersed in a beaker containing electrolyte and is connected to the circuit bath. The circuit can be completed by the human subject immersing a finger in the beaker with the reference electrode. The reliability of this approach is characterized by two control experiments. One involves the insertion of a salt bridge filled needle subcutaneously where a connected tube is immersed in the reference electrode beaker. The other control experiment uses a second identical reference electrode placed in the beaker. Electrical contact between this reference electrode and the human subject is made by physical contact at the second reference electrode lead. These two control experiments suggest no difference in the applied potential at the working microelectrode compared to experiments conducted with the human subject’s finger inserted in the beaker. However, completing the circuit by placing a copper wire in the reference electrode beaker, where the human subject physically contacts the dry air-end of the wire, does show evidence of an altered applied potential at the working microelectrode.
(Invited) Si Anodes for Li-Ion Batteries: Experimental Studies on Li-Inventory and Pre-Lithiation Approaches
Authors: Dose Wesley M , Blauwkamp James , Johnson Christopher S.
Published: February 2020

Li inventory and pre-lithiation methods for Si-anode containing Li-ion batteries are evaluated via a number of avenues, and are summarized briefly in this abstract. The capacity fade of the Si-graphite electrode was tracked using a capacity over-sized LiFePO4 cathode in a diagnostic cell. With essentially limitless Li inventory the intrinsic capacity fade was monitored over hundreds of cycles, without limitations/complications from Li metal in a half cell. The introduction of lithium inventory to the cell was accomplished in three ways. To date we have (1) investigated in detail the synthesis and electrochemistry of Li5FeO4 as a prelithiation source. Approach #1. We are currently working towards a blended LFO-NMC cathode to understand the cross-reactivity, impedance changes, and capacity changes in the resultant electrode. (2) Introducing lithium inventory to the cell #2. Overlithiated NCM, i.e., Li1+xNCM523O2, was found to be a viable way to introduce lithium to the cathode with minimal weight increase and no residual byproduct. However, we observed that the electrochemical cycling stability of overlithiated NCM is compromised, likely a result of the irreversible anisotropic structural changes. Work is ongoing to assess the nature of the irreversibility and we are developing strategies to minimize its impact. (3) Introducing lithium inventory to the cell #3. We will report that the 5 V spinel cathode, or Li1+xNi0.5Mn1.5O4, could be further lithiated (x>0) via an ammonia-based chemical lithiation reaction. This material was paired with a Si-graphite anode in a full cell. The excess lithium is released during the first charge and accounts for the first cycle irreversible capacity loss. Subsequent cycling only at 3 to 4.7 V shows a higher capacity and similar fade rate compared to the baseline, un-lithiated cathode.
Influence of Electrode Design and Lithium Source Format on the Performance Metrics of Pre-Lithiation of Anodes in an Energy Storage Device
Authors: Shellikeri Annadanesh , Zheng Jim P.
Published: February 2020

Energy storage devices like batteries and supercapacitors, have become the crucial part of electrification of transportation. Better and more efficient energy storage devices are the need of the hour, critical to achieving this goal. In our earlier work [1,2], we have shown that several fabrication and design measures, like an advanced dry method of electrode fabrication, an optimized design of anode to cathode capacity ratio, an array of pre-lithiation methods, a composite cathode, etc., can be ingeniously combined to enhance the performance characteristics of energy storage devices in terms of specific energy (Wh.kg-1), specific power (W.kg-1), cycle life and cost.

Among these performance enhancing measures, the process of pre-lithation is a necessary measure on multiple fronts, namely, to compensate for the initial cycle loss from solid electrolyte interface formation on anodes, to improve first cycle coulombic efficiency, to prevent the loss of active Li content in electrolyte and to achieve an improved cell working voltage range by initially driving the anode potential to lower permissible limits. We have also shown in our previous work [3] that an array of Li metal sources can be employed for achieving pre-lithiation through the internal short method in carbon electrodes. Over a time limited condition, we demonstrated the importance of different lithium source structures and their effect on the rate of pre-lithiation and pre-lithiation capacities that can be achieved.

In our present work, we have eliminated the time limiting condition, allowing for the complete ionization of the Li-sources employed, hence enabling a complete pre-lithiation process in all Li-source formats that were employed. We have also performed a comparative study between the internal short circuit method of pre-lithiation and the external short circuit method. Different Li-source formats, based on their surface area and structure, exhibit different ionization and pre-lithiation speeds, capacities and efficiencies. Fig. 1 presents an illustration of different pre-lithiation methods organized based on their speed of pre-lithiation, with the fastest process being stabilized Li-metal powder (SLMP - leftmost) and slowest of the pre-lithiation processes occouring in lithium strip in electrode gap method and in an external short circuit method using an appropriate current limiting resistor (rightmost). On account of spherical micro nature of SLMP particles, they possess a larger active surface area for the ionization process to continue more vigorously and hence faster speed of pre-lithiation. Our analysis of reversible capacities after pre-lithiation, electrode cycle life, DC life, safety and cost aspects, etc., will also be presented.

Figure 1
Effect of Stress on Li Transport in High Energy Density Electrode Materials
Authors: Rakshit Subhajit , Pakahare Akshay , Bezsonov Igor , Nadimpalli Siva
Published: February 2020

Solid-state diffusion of lithium through the active material is a crucial aspect of lithium-ion battery operation. Quantitative analysis of transport properties is important to understand diffusion mechanisms and designing effective electrode architectures for Li-ion battery. There is a large body of literature exists on Li diffusion coefficient measurement techniques in various electrodes, among them, galvanostatic intermittent titration technique (GITT) and the potentiostatic intermittent titration technique (PITT) are the most widely used methods. However, none of the existent studies considered electrode stresses and the effect of stresses on the measured chemical diffusion coefficient. In this study, sputter deposited Ge films (as a model high energy electrode material) were subjected to potentiostatic intermittent titration technique (PITT) and galvanostatic intermittent technique (GITT) conditions while simultaneously measuring the stress evolution in the electrodes. It was observed that the stresses varied significantly in a single titration step during GITT experiment, which violates the assumptions of Fickian transport model where the electrode stresses are usually neglected. Therefore, only PITT data was analyzed to obtain the chemical diffusion coefficient of Li in Ge. As expected, the diffusion coefficient value increased considerably with Li concentration; however, the values obtained during delithiation are at least two times higher than those obtained during lithiation at any given concentration, with the difference becoming significantly higher with Li concentration. This difference is attributed to the state of stress, i.e., tensile state of stress enhances diffusion and compressive state of stress impedes the diffusion process. The data and observations presented here will be helpful in developing and using electro-chemo-mechanical models in producing optimized electrode microstructures.
Investigating SEI Formation Methods on the Graphite Anode Interface Using Nuclear Reaction Analysis
Authors: Flottman Spencer , Chebuske Matthew , DeRosa Donald M , Higashiya Seiichiro , Efstathiadis Harry , Antonopoulos Konstantinos Byron , Maglia Filippo , Gittleson Forrest S , Paschos Odysseas
Published: February 2020

Observing and managing the functional characteristics of solid electrolyte interphases (SEIs) has been a central topic in lithium-ion battery research for many years. Recently, Antonopoulos et al. reported that forming SEIs on composite graphite electrodes in a high-potential region (1.2 - 0.78 V vs. Li/Li+) has a significant influence on rate capability in half cell formats. [1] In our work, we reviewed several formation methods in full cell devices and studied their impact on the SEI via Li nuclear reaction analysis (Li-NRA) measurements on post-mortem electrodes. This novel technique was previously used to study Li-ion electrode interfaces by Schultz et al. (2017). By detecting gamma emissions from the reaction [7Li (p,γ)8Be] between incident hydrogen ions of specific energies and Li in the sample, we obtained a qualified Li content profile. The NRA results were compared with secondary ion mass spectrometry (SIMS) depth profiles and X-ray photoelectron spectra (XPS). These profiles showed relatively high levels of lithium in the surface region of the anode (~150 nm deep) with variation among electrodes using different formation procedures. This finding, connected with a reduced rate capability for some cells, implies that the buildup of Li at the anode interface may be an important factor influencing the full cell performance after formation.
Investigating the Origin of Cation Mixing in Nickel Rich Cathodes
Authors: Muralidharan Nitin , Essehli Rachid , Self Ethan Craig , Nanda Jagjit , Belharouak Ilias
Published: February 2020

*corresponding authors email: muralidharan@ornl.gov and belharouaki@ornl.gov

Lithium Ion Batteries Have Been the Catalyst That Brought about the Revolution of Portable Electronic Devices and Electric Vehicles. with the Ever-Increasing Promise of Novel Anode Formulations Delivering Higher Capacities, the Present-Day Energy Densities Are Limited By the Choice of Cathode Used. with Recent Research and Development Trends Focused Heavily on the Class of Layered Nickel Rich Cathodes (LiNixM1-xO2, where M=Transition Metal Cation, x>0.6), It Is of Categorical Importance to Understand the Limiting Mechanisms Hampering the Performance of Such Cathode Systems. of Particular Importance Is the Intermixing of Cations, Ni2+ and Li+ between the Lithium and Transition Metal Slabs in These Layered Cathodes Owing to Their Similar Ionic Radii. These Ni2+ions in the Lithium Slab Creates Li+ Ion Migration Bottlenecks Thus Resulting in the Under-Utilization of the Total Available Storage Capacity of These Cathode Materials. Our Work, Utilizing in-Situ X-Ray Diffraction and Mossbauer Spectroscopy during the Synthesis Procedures Aims to Reveal the Role of Specific Transition Metal Cation Dopants in Lowering/Increasing the Extent of Cation Mixing and the Resulting Electrochemical Behavior of Nickel Rich Cathode Systems Such As the LiNi0.8CoxAlyO2(NCA class) and the LiNi0.8CoxMnyO2 (NCM class). Overall, This Work Provides a Broad Framework to Understand, Isolate and Mitigate This Limiting Phenomena in the Development of Next Generation Lithium Ion Battery Cathodes.
Reduction of Electronic Conductivity within Secondary Particles Revealing a Degradation Mechanism of Ni-Rich Cathode for Lithium Ion Batteries
Authors: Kim Jae-Hyung , Nam Gyeong Won , Sun Yang-Kook
Published: February 2020

A locally reduction in electronic conductivity in the core region of secondary particles is proposed as a capacity-fading mechanism of a Ni-rich cathode. This is investigated by measuring the electronic conductivity of the secondary particles of Li[Ni0.98Co0.01Mn0.01]O2 using the scanning spreading resistance microscopy (SSRM) mode of atomic force microscopy. SSRM analysis reveals that a much thicker rocksalt phase, which is transformed from the original layered structure, on the surface of the primary particles in the core region electronically disconnects the primary particles from the neighboring particles. Intercalation and deintercalation of Li are hindered in the electronically insulated primary particles. Thus, detecting of the local electronic conductivity in the secondary particles confirms that the loss of electronic conductivity in the core region of the secondary particle is a important factor in the degradation mechanism of a Ni-rich cathode for lithium ion batteries.

References:

[1] H.-J. Noh, S. Youn, C. S. Yoon, Y.-K. Sun, J. Power Sources
2013, 233, 121.

[2] K.-J. Park, H.-G. Jung, L.-Y. Kuo, P. Kaghazchi, C. S. Yoon, Y.-K. Sun, Adv. Energy Mater.
2018, 8, 1801202.

[3] C. S. Yoon, D.-W. Jun, S.-T. Myung, Y.-K. Sun, ACS Energy Lett.
2017, 2, 1150.

[4] C. S. Yoon, H.-H. Ryu, G.-T. Park, J.-H. Kim, K.-H. Kim, Y.-K. Sun, J. Mater. Chem. A
2018, 6, 4126.
Investigating the Effects of Magnesium Doping in Various Ni-Rich Materials
Authors: Liu Aaron , Li Hongyang , Zhang Ning , Inglis Julie , Dahn Jeff R
Published: February 2020

As lithium ion battery technology expands into more demanding applications such as electric vehicles, attention has shifted towards nickel-rich positive electrode materials, namely LiNi1-x-yMnxCoyO2 (NMC) and LiNi1-x-yCoxAlyO2 (NCA).1 Aims to improve energy density and reduce costs of NMC and NCA can be achieved by increasing the Ni content of the material, but at the cost of shorter cell lifetimes.

Besides Al, Co and Mn, research has tried substituting Ni with many different metals.1 Mg has repeatedly come up as a beneficial dopant from positive electrode material doping studies that try to improve material cycling performances. Mg has been shown to improve cycling performances of various positive electrode materials including LiCoO2 (LCO), NMC, and NCA when doped into the material in small amounts.1–4 Doping the material with Mg slightly reduces the specific capacity of the material since Mg is an inactive constituent, but it has been shown that a Mg content of as low as 1 mol% can improve cycling.3

LiNiO2 (LNO) and some other Ni-rich materials undergo phase transitions as Li gets removed during charging. In particular, when the material transitions from the H2 phase to the H3 phase at low Li, it experiences a large volume change. It is believed that this contributes to a poor lifetime of the material. Mg doping has been shown to suppress these phase transitions and related volume changes.2,4 Mg has also been shown to reduce the amount of Ni migration to the Li layer.1

As research continues to increase the Ni content of NMC and NCA, the compositions will invariable converge towards LNO. Additionally, efforts are being made to reduce the Co content of Ni-rich materials due to cost and sourcing issues.4 Co is believed to reduce the amount of Ni in the Li layer and also to stabilize cycling performance, which are similar benefits that Mg imparts. This work studies the effect of Mg doping in LiMO2 (M = Ni, Ni+Al, Ni+Co+Al, Ni content > 0.8) at a dopant level of less than 5 mol%. Structural and electrochemical characterization of the materials was carried out to understand how Mg affects the materials and whether the presence of Al or Co influences the dopant effects of Mg. Figure 1 shows the initial half-cell voltage vs capacity and differential capacity vs voltage curves for a series of LiNi0.88-xCo0.09Al0.03MgxO2 (x = 0, 0.01, 0.02, 0.04) materials, showing a trend of how Mg affects the electrochemical performance of the materials.

(1) Kim, J.; Lee, H.; Cha, H.; Yoon, M.; Park, M.; Cho, J. Adv. Energy Mater.
2018, 8, 1–25.

(2) Sasaki, T.; Godbole, V.; Takeuchi, Y.; Ukyo, Y.; Novák, P. J. Electrochem. Soc.
2011, 158, A1214–A1219.

(3) Huang, B.; Li, X.; Wang, Z.; Guo, H.; Xiong, X. Ceram. Int.
2014, 40, 13223–13230.

(4) Li, H.; Cormier, M.; Zhang, N.; Inglis, J.; Li, J.; Dahn, J. R. J. Electrochem. Soc.
2019, 166, A429–A439.

Figure 1
A Novel Approach to Recycle Precious Metals from Spent Li-Ion Batteries
Authors: Xiong Shan , Han Aijie , Ma Xuetian , Chen Hailong
Published: February 2020

With rapidly increasing demand of Li-ion batteries (LIBs) triggered by the widespread proliferation of mobile devices and electric vehicles, a comprehensive and clean recycling strategy is greatly desired to alleviate the pressure of waste treatment and raw material supply. In this study, a novel method is developed for the recovery of semi-precious metals (Li, Co and Ni) from spent LIBs based on low temperature solution reactions, which is different from conventional acid leaching or high temperature smelting recycling methods. This novel recycling method can be applied to most of the prevailing commercial cathode materials, including LiCoO2(LCO), LiNixMnyCozO2 (NMC), and LiNi0.8Co0.15Al0.05O2 (NCA), with high recovery rates of 93%~99%. In situ synchrotron XRD is conducted to reveal the reaction mechanism and optimize the reaction conditions. A scaled-up recycling test towards industrial applications is also proposed based on the solution reactions. The experimental results suggest this novel method can be easily adopted for industry-level LIB recycling processes in an efficient and environmentally friendly way. A life cycle analysis has also been conducted to confirm the economic and energy/emission feasibility of this approach. Therefore, this approach shows great promise as a next-generation scenario for the recycling of high-value metals from spent commercial LIBs in the near future.

Figure 1
Strategy of Enhancing Energy Density of Layered Ni-Rich Li[Ni1-2xCoxMnx]O2 Cathodes (x = 0.05, 0.1, 0.2)
Authors: Kim Jae-Hyung , Nam Gyeong Won , Park Nam-Yung , Aishova Assylzat , Yoon Dae Ro , Sun Yang-Kook
Published: February 2020

Recently, Ni-rich layered Li[Ni1-2xCoxMnx]O2 (NCM, x ≤ 0.2) cathodes show high capability for increasing the energy densities which is essential to facilitate the penetration of electrified transportation systems into the automobile market. However, the poor thermal stability of these cathodes is retarding their commercialization. In this study, the effect of Ni content and upper cut-off potential on the electrochemical and thermal properties of Ni-rich NCM cathodes (NCM-622, 811, 90) is evaluated to identify the optimum composition of the cathodes and the cycling conditions. This research shows that operating Ni-rich cathodes at higher cut-off potentials (> 4.3 V) rather than progressing to highly nickel enriched compositions can be a better method of enhancing their energy densities and maintaining adequate thermal stability. It is shown that a Li[Ni0.6Co0.2Mn0.2]O2 (NCM-622) cathode cycled up to 4.5 V exhibits a discharge capacity of 200 mAh g-1 and capacity retention of 93% after 100 cycles, which are similar to the ones of Li[Ni0.8Co0.1Mn0.1]O2 (NCM-811) cycled up to 4.3 V. Similar volume change during cycling and comparable NiO-like rocksalt impurity layer after 100 cycles in both of the cathodes may be the reason for their similar cycle lives despite operating at different charge cut-off potentials. In spite of the comparable capacity and retention, NCM-622 cathode exhibits superior thermal stability, in which the occurrence of the exothermic reaction is delayed by 50 °C, than NCM-811. In addition, analogous trends are observed in the cathodes with higher nickel compositions, i.e., NCM-811 and Li[Ni0.9Co0.05Mn0.05]O2 cycled up to 4.5 V and 4.3 V, respectively.

Reference
s
:

[1] Y.-K. Sun, S.-T. Myung, H. J. Bang, B.-C. Park, S.-J. Park, N.-Y. Sung, J. Electrochem. Soc.
2007, 154, A937.

[2] H.-H. Ryu, K.-J. Park, C. S. Yoon, Y.-K. Sun, Chem. Mater.
2018, 30, 1155.

[3] U.-H. Kim, E.-J. Lee, C. S. Yoon, S.-T. Myung, Y.-K. Sun, Adv. Energy Mater.
2016, 6, 1601417.

[4] C. S. Yoon, H.-H. Ryu, G.-T. Park, J.-H. Kim, K.-H. Kim, Y.-K. Sun, J. Mater. Chem. A
2018, 6, 4126.
The Correlation between the Particle Morphology and the Electrochemical Stability for High-Ni Cathode and Understanding of the Mechanism of Parasitic Reaction.
Authors: Gim Jihyeon , Liu Tongchao , Yonemoto Bryan T , Shin Youngho , Estevez Luis , Ren Yang , Croy Jason R. , Chen Zonghai , Amine Khalil
Published: February 2020

Understanding the correlation between physical and electrochemical/chemical properties are significantly crucial for the development of electrode materials for lithium ion batteries. Among the cathode materials, high-Ni cathode with high energy density has a degradation issue of electrochemical performance due to the parasitic reaction at the cathode electrolyte interface. The core-shell or full concentration gradient materials consisting of a high-Ni core and a relatively high-Mn outer layer might be a potential candidate providing the improved electrochemical stability as well as cycle life performance. In this respect, the porosity of the final sintered particle is the key to affect the electrochemical stability indicating the side reaction with organic liquid electrolyte. The strategy tuning the particle porosity and density is applied to synthesize different particle size of transition metal precursor during co-precipitation. The structural characteristics are compared for the materials with different physical properties by utilizing ex-situ or in-situ X-ray diffraction, electron microscopy, electrochemical performances, and particle size distribution. The interfacial kinetic reaction between the Ni-rich cathode and a nonaqueous electrolyte at different SOCs is investigated by our home-built high-precision leakage current measurement system. This study can give us a clear sight for understanding the mechanism of parasitic reaction as well as providing a solution for the safety issue of the high-Ni cathode in lithium ion battery.
Molecular Dynamics Simulation Study of Ion Transport, Structural and Mechanical Properties of Li2CO3 and Mn-Li-CO3
Authors: Ebrahiminia Mahsa , Wang Cun , Hooper Justin B. , Bedrov Dmitry
Published: February 2020

In this study, we focus on understanding properties of the Solid Electrolyte Interphase (SEI), which plays an important role in the performance of Li-ion batteries. SEI has a complex structure including domains and blends of different organic (such as LEC, LMC, Li2EDC, etc.) and inorganic compounds (such as LiF, Li2O, etc.) which are byproducts of single and double electron reduction processes of electrolyte solvent and ions. Because of this complexity, the detailed structure and characteristics of SEI are still not well understood.

Dilithium carbonate, Li2CO3, is known to be one of the important and stable compounds in the SEI structure. While there were some studies considering crystal phase of Li2CO3, the properties of amorphous glassy phase that can form at the domain boundaries within SEI or under fast rates of electrolyte reduction has not been investigated. In addition to SEI, amorphous blends of Li2CO3 with other oxides have been considered as potential materials for solid electrolytes. To the best of our knowledge, we present the first study considering the amorphous phase from theoretical point of view.

Using atomistic MD simulations and a polarizable force field, we investigated properties of amorphous Li2CO3 phase and predict structural, dynamical, and mechanical properties of Li2CO3 as a function of temperature as well as the content of Mn2+ in the SEI. The latter investigates the influence of SEI “contamination” by divalent cations dissolved from high-voltage cathods or intentional introduction of sacrificial divalent cation salts to promote formation of denser and stronger SEI.

According to our study, Mn0.2Li1.6CO3 forms the glassy state below 600 K, which is a 150 K increase compared to Li2CO3 system. Besides, Mn0.2Li1.6CO3 shows 15% higher density. From mechanical property calculations, shear modulus value for Li2CO3 is around 8 GPa, while it increases significantly with the addition of Mn2+.
Enabling High Temperature Lithium Ion Batteries through NMR Analysis
Authors: Johnson Noah Mark , Zhang Zhengcheng
Published: February 2020

Lithium ion batteries experience rapid capacity fade at elevated temperatures. Solving this problem would expand the applications for this technology, but relies upon an imperfect understanding of the degradation mechanisms occurring within a cell. In this work, we present an analytical method using NMR which can give insight into the process by which electrolyte decomposes at high temperatures, as well as evaluate the effectiveness of mitigation strategies. By intentionally adding impurities and changing conditions, we can study the degradation of the bulk electrolyte during thermal aging by separating the effects of different factors, and therefore understand how to prevent the process from occurring.