bluuebunny/crossref_metadata_2025 huggingface dataset:
Iron Porphyrin Carbenes As Intermediates in the Degradation of Toxic Compounds and Catalysis: Structures, Spectroscopic Properties, and Bonding
Authors: Khade Rahul , Fan Wenchao , Ling Yan , Yang Liu , Zhang Yong
Published: February 2020

Iron porphyrin carbenes (IPCs) are thought to be intermediates involved in the metabolism of various xenobiotics by cytochrome P450, as well as in chemical reactions catalyzed by metalloporphyrins and engineered P450s. While early work proposed IPCs to contain FeII, more recent work invokes a double bond description of the iron carbon bond, similar to that found in FeIV porphyrin oxenes. Here, we report the first quantum chemical investigation of IPC Mössbauer and NMR spectroscopic properties, as well as their electronic structures, together with comparisons to ferrous heme proteins and an FeIV oxene model. The results provide the first accurate predictions of the experimental spectroscopic observables as well as the first theoretical explanation of their electrophilic nature, as deduced from experiment. The preferred resonance structure is FeII<--{:C(X)Y}0 and not FeIV={C(X)Y}2-, a result that will facilitate research on IPC reactivities in various chemical and biochemical systems.
New Generation of Hybrid Materials Based on Hierarchical Assembly of Porphyrin on Supramolecular Scaffolds or Nanostructures
Authors: Fragalà Maria Elena , D'Urso Alessandro , Randazzo Rosalba , Cristaldi Domenico Andrea , Purrello Roberto
Published: February 2020

Porphyrins multifunctional properties make these macrocycles intringuing building blocks to build up complex supramolecular assemblies via covalent or non-covalent approaches, either in solution or on inorganic surfaces. In the perspective of development of hybrids organic-inorganic materials, mastering of non-covalent strategies to transfer water soluble porphyrin based assemblies on nanostructured surfaces paves the way to a cost effective and environmentally friendly research that combine the unique properties of nanomaterials with the synthetic versatility of organic chemistry. Noteworthy, the control of spontaneous self-assembly is not trivial, as it is a hierarchically driven process that can proceed through thermodynamic or kinetic pathways. However, in water, complex porphyrin based supramolecular assemblies having a pre-determined and controlled  stechiometry, chirality and composition have been successfully synthetized. Transfer of these assemblies (i.e. chiral porphyrin chiral aggregates, porphyrin-calixarenes, porphyrin-DNA) on inorganic surfaces opens the way to development of new generation of chiral surfaces and sensors, where porphyrins played an important role as spectroscopic probes, capable to overcome sensitivity limitations. Chirality induction and memory is, accordingly, another important requirement that need to be kept during this migration from solution to the solid state. The robustness of non-covalent approaches to achieve a straightforward, controllable and environmentally friendly functionalization of inorganic nanostructures strongly hinges on the competition between retention at the solid state rather than in solution and depends on several factors. Among them, polyelectrolytes secondary structure strongly influences the outcome of spontaneous deposition of porphyrin assemblies on solid surfaces often overriding the mere system electrostatics.
Functionalized Pi-Extended Porphyrins
Authors: Wang Hong , Jinadasa Raja Gabadage , Kumar Siddhartha , Schmitz Benjamin , Miller Ethan , Kadish Karl M. , Fang Yuanyuan
Published: February 2020

Pi-extended porphyrins have remained a long-lasting research interest in scientific fields due to their unique set of photophysical and optoelectronic properties as well as their potential broad application in various areas ranging from biomedicine to organic electronics. However, due to the limited synthetic methods, particularly the lack of functionalization methods, only a small number of pi-extended porphyrins have been studied in the past decades. In order to make breakthrough in the synthesis of pi-extended porphyrins, our group has developed concise and versatile methods, the availability of which opens the door to access a large number of functionalized pi-extended porphyrins. In this presentation, we report the synthesis and characterization of three new classes of pi-extended porphyrins, including push-pull dibenzoporphyrins, A2B2
push-pull tetrabenzoporphyrins, and acene-fused porphyrins oligomers. The electronic and optical properties of these p-extended porphyrins were measured using UV-Vis spectroscopy, steady state fluorescence spectroscopy, and cyclic voltammetry. DFT calculations were also performed for these porphyrins.

Figure 1
Synthesis of Benzoporphyrin-Diketopyrrolopyrrole Conjugates and Application for Organic Solar Cells
Authors: Kuzuhara Daiki , Takahashi Kohtaro , Yamada Naoya , Yamaguchi Yuji , Suzuki Mitsuharu , Aratani Naoki , Nakayama Ken-ichi , Yamada Hiroko
Published: February 2020

Organic solar cells (OSC) have great attractive attention as key technology for next energy harvesting source. They could be fabricated for low cost, large area and flexible devices. However, power-conversion efficiency (PCE) of OSC is limited compared with the inorganic materials-base solar cell. Therefore, OSC requires new organic functional dyes for OSC for the improvement of PCEs. Benzoporphyrin (BP) has a expanded structure with four benzannulation at pyrrolic β-position on porphyrin core. BP has a highly planer structure and excellent semiconducting properties. Ono and colleagues　have developed the thermal-convertible precursors of BP, namely bicycle[2,2,2]octadiene-fused porphyrin (CP). 
CP can be converted to BP under heating conditions by retro-Diels-Alder reaction. This thermal conversion method allowed us to fabricate the multi-layered OSCs by solution process. However, the nature of BP has the problems and limitations for improvement of the PCE because BP has weak absorption in the NIR regions and the HOMO level of BP is higher than that of ideal donor materials for OSC. It is known that improvement of the PCE is necessary for the wide-range absorption in the visible to NIR regions and appropriated HOMO and LUMO levels.  In this presentation, we will report the design, synthesis and properties of the benzoporphyrin-diketopyrrlopyrrole conjugates (BP–DPP) for the p-type material of the PCEs. The absorption spectrum of BP–DPP was measured as thin film on glass substrate. The absorption of BP­–DPP shows broader absorption with four peak tops from visible to NIR regions.  We have fabricated the bulk heterojunction (BHJ) type OSC with BP–DPP as p-type material and PC61BM as n-type material. The PCEs of 4.0% for BP–DPP:PC61BM was achieved with short-circuit current (J
SC) of 12.47 mA cm-2, open circuit voltage (V
oc) of 0.68 V, and fill factor (FF) of 0.47.We will also report the evaluations of film structures of these devices by AFM and XRD measurements.
Modulating Strain and Charge Transfers in Low Dimensional Catalysts through Interface Design and Templated Growth
Authors: Alamgir Faisal M , Vitale Adam
Published: February 2020

In this presentation, we review the dimensional aspects of structure-driven surface properties of metal monolayers grown on a Au and graphene/Au templates. Here, surface limited electrodeposition is used to provide precise layer-by-layer growth of Pt monolayers. After a few iterations of SLRR, we find that fully wetted 4-5 monolayer Pt films can be grown on either template. Incorporating graphene at the Pt-Au interface modifies the growth mechanism, charge transfers, equilibrium interatomic distances and associated strain of the synthesized Pt monolayers. Capping the Pt with a single overlayer of graphene similarly affects the underlying Pt structures. X-ray photoelectron spectroscopy (XPS) and extended x-ray absorption fine structure (EXAFS) techniques are used to examine charge mediation across Pt-Graphene-Au junction and the local atomic arrangement as a function of the Pt adlayer dimension. Cyclic voltammetry (CV) and the oxygen reduction reaction (ORR) are used as probes to examine the electrochemically active area of Pt monolayers and catalyst activity, respectively. Results show that the inserted graphene monolayer results in increased activity for the Pt due to a graphene-induced compressive strain, as well as a higher retention of catalytically active Pt surface. This Pt retention extremely effective, and occurs with no compromise to ORR activity, when the Pt is capped with a graphene layer.
Effect of Temperature on Characteristics of Pt/C Gas-Diffusion Electrode Used in Electrodeposition of Manganese Dioxide for Saving Energy
Authors: Meng Huimin , Tang Jing
Published: February 2020

We have researched a new energy-saving and environmentally friendly method for electrodeposition of manganese dioxide using a Pt/C gas diffusion electrode as cathode instead of the traditional cathode. Our previous research has been published. Here we research that temperature dependence of characteristics of Pt/C GDE at various temperatures for saving energy and green electrodeposition of manganese dioxide. The gas-diffusion electrode based on Pt/C catalyst (Pt/C GDE) is prepared by rolling method. The Pt/C catalyst is 3-4nm. The Pt loading was 0.68±0.02 mg/cm2. The gas-diffusion electrode based on Pt/C catalyst is investigated in 30g/dm3 H2SO4 +120g /dm3 MnSO4 in the temperature range 30-90°C. The activity of the Pt/C GDE increases at first and decreases afterwards and then again increased with rising temperature. The current of the Pt/C GDE is 0.01057A/cm2, 0.0199A/cm2, 0.01579 A/cm2, 0.01704 A/cm2 at 30, 50, 70 and 90°C at -0.4V/Hg/HgSO4. The cell voltage can decrease 40%, 45%,47% and 45.8% compared with that of the traditional cathode in 100s at 30, 50, 70 and 90°C, respectively. The oxygen reduction reaction mechanism of the Pt/C GDE used in electrodeposition of manganese dioxide does not change.
Recovery of Erbium Metal Via Electrorefining in Room Temperature Ionic Liquids
Authors: Small Leo J. , Wheeler David R. , Lambert Timothy N. , Hess Ryan F.
Published: February 2020

Erbium is a rare earth element with a variety of technologically important applications.  Here we describe our efforts to develop room temperature ionic liquids specifically designed to facilitate electroplating of erbium metal from erbium chloride or erbium triflate, in an effort to recycle erbium waste converted into these salts.  A variety of pyrrolidinium, ammonium, phosphonium, and chloroerbate ionic liquids are investigated.  While all tested ionic liquids possess the required voltage window for theoretical erbium electroreduction, choice of chemistry is shown to drastically affect both incorporation of organics into the electrodeposited film, and the solubility of erbium salt in the ionic liquid, limiting deposition rates.  A plan-view SEM micrograph of an amorphous erbium film electroplated onto platinum in butyltrimethylammonium bis(trifluoromethanesulfonyl)imide (BTMA NTf2) is shown in Figure 1.  Analysis by energy dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy reveals incorporation of fluorocarbons into the film.  These undesirable processes are not readily evident from the simple cyclic voltammograms (Figure 2).  Detailed analysis of these CVs suggests reversible reduction of an intermediate followed by irreversible reduction to an erbium film contaminated with fluorocarbons.  

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Figure 1
(Invited) Spray Coating of Organic Semiconductors and Carbon Nanotube Electrodes for Solar Cells
Authors: Rand Barry P. , Tait Jeffrey
Published: February 2020

The promise of solution processed organic solar cells lies in their low-cost high-throughput manufacturability. However, this low cost aspect can only be fully realized if all of the layers are deposited via in-line compatible methods. Spray coating is a high-rate, non-contact deposition technique characterized by the ability to deposit thin films over large areas by the superposition of small droplets. Here, we discuss our recent efforts in utilizing concurrently pumped ultrasonic spray coating, whereby two solutions are pumped to a vibrating nozzle and simultaneously atomized. With this technique, we are able to control solution concentration, donor:acceptor ratio, and multiple-solvent composition, giving us a method by which to optimize not only the smoothness and thickness of the dried film but also the active layer composition. Also, we will show our results with depositing patterned top and opaque electrodes composed of either metallic nanoparticles sintered upon deposition or multiwalled carbon nanotube (MWCNT)-based inks. Notably, despite the absorptive nature of a back MWCNT electrode, devices are able to exhibit ~85% of the photocurrent compared to an evaporated Ag top contact.
(Invited) Surface-Mediated Molecular Assembly of Organic Semiconductors for High-Performance Organic Electronics
Authors: Cho Kilwon
Published: February 2020

Microstructure in organic semiconductor thin films has been regarded as the key factor determining the performance of the organic electronics. In case of bottom-contact organic field effect transistors (OFETs) and organic photovoltaics (OPVs), the control of the surface characteristics of the underlying substrates can govern the mesoscale and/or nanoscale ordering of the semiconductor assembled on them. Here, we present various approaches for controlling the growth of organic semiconductors on the gate dielectrics and electrodes to achieve high performance OFETs and OPVs.
Impact of Surface Texturization on Overall Performance of Mono-Crystalline Silicon Solar Cells
Authors: Sankarasubramanian Shrihari , Saud Gaurav Kumar , Shashikala M , Suratkar Prakash , Saravanan S
Published: February 2020

Solar photovoltaics are amongst the foremost and most extensively studied sustainable energy systems. Silicon solar cells dominate commercial systems and hence bringing them ever closer to the theoretical efficiency is of vital importance. Technologists are continuously refining the manufacturing process to improve the efficiency of the cell while bringing down the cost. 

The Silicon solar cell manufacturing is a complex process with many vital steps. Studies have shown the importance of steps like surface texturization[1], diffusion[2], antireflective coatings[3], making contacts[4] and metallization[5]. Amongst these the maximum impact on the final efficiency of the solar cell was found to come from the surface texturization[7]. This step creates surface features that improve light harvesting by the multi bounce approach. While heuristically it is understandable that the reduction in reflectivity would impact the cell performance, the present study aims to quantify this improvement.

To that end, two different processes were used to texture the mono-crystalline silicon wafers, the difference being the bath additives used. The studies were carried out on 125x125 mm mono-crystalline silicon (C-Si) wafers. The wafer reflectivity and texture uniformity were studied using a full spectrum colourimeter. The wafers were then processed into finished cells and the I-V characteristics of these cells were evaluated.  The various performances characteristics of the cell were statistically analyzed to study there correlation to the reflectivity. 

References:

P. Papet, O. Nichiporuk, A. Kaminski, Y.  Rozier, J. Kraiem, J.F. Lelievre, A.  Chaumartin, A. Fave, M. Lemiti, Sol. Energy Mater. Sol. Cells. 90,  2319–2328, 2006.

D. Kumar, S. Saravanan,  P. Suratkar, J. Ren. Sus. Energy. 4(3), 33105-33113, 2012.

K. Coates, S. Morrison, S. Narayanan, A. Madan, in Proc. 16th Eur. Photovol. Sol. Energy Conf. Glasgow, 1279-1281, 2000.

P.S. Aakella, S. Saravanan, S.S. Joshi, C.S. Solanki, Sol. Energy. 97, 388-397, 2013.

M.M. Hilali, K. Nakayashiki, C. Khadilkar, R.C. Reedy, A. Rohatgi, A. Shaikh, S.  Kim, S.  Sridharan, J. Electrochem. Soc. 153(1), A5-A11, 2006.

J. D. Hylton, A. R. Burgers,W. C. Sinke, J. electrochem. Soc., 151 (6) G408-G427 (2004).

Figure 1
Transient Photocurrent in Organic Photocells Assisted By Electric Double Layers in Electrolytes
Authors: Odaka Masato , Matsushita Michio M , Awaga Kunio
Published: February 2020

Recently, there has been increasing interest in photoelectric conversion by organic semiconductors. Organic materials have many advantages over inorganic materials, such as the possibility of low temperature, and thus low cost processing, which allows for flexible architectures to be realized. However, to date, organic device performance still lags behind that of inorganic devices. It is our aim to use the intrinsic properties of organic materials to develop novel operation principles for organic devices, to rival the performance of inorganic devices.

In previous works, our group has reported on anomalous transient photocurrents induced by a multi-layer photocell architecture, which incorporates a polarizable insulating layer to aid charge separation in the active semiconductor layer. More recently, we reported the use of ionic liquids as the insulating layer. Such architectures generate a time-varying (transient) response to continuous illumination, which may have an application to optical communication. In these devices, The electric double layers in ionic liquid enhance the charge separation in the active layers and generate an anomalous transient photocurrent.

In this work, we adopted the KCl aqueous solution to the insulating layer, instead of ionic liquids. Figure.1 shows the transient photocurrent with several concentration KCl aqueous solutions. The transient photocurrent was obtained ever with a small amount of KCl. Furthermore, there is a concentration dependence of the peak values and the relaxation times of the transient photocurrents.

Figure 1
A Novel Approach to Study the Chemo-Mechanical Stability of the Solid Electrolyte Interphase (SEI) in Lithium-Ion Batteries
Authors: Kumar Ravi , Xiao Xingcheng , Lu Peng , Sheldon Brian W.
Published: February 2020

It has been recognized that a stable solid electrolyte interphase (SEI) is critical in operation of rechargeable Li-ion batteries. A clear understanding of SEI formation, evolution and mechanical response will make it possible to tailor better passivation layers that can improve battery performance. In this work we present a novel approach that is based on patterned Si islands, with measurements that include galvanostatic cycling, electrochemical impedance spectroscopy (EIS), in situ optical microcopy, and in situ stress measurements. By calibrating the expansion and contraction of these islands, it is possible to systematically investigate the impact that large volume changes have on the SEI stability. Comparisons between these islands and continuous Si films then make it possible to correlate the irreversible capacity loss with expansion strain in the underlying Si. These galvanostatic experiments on island samples provide a novel mechanical testing configuration for investigating the stability of thin SEI layers.
In-Situ Raman Spectroscopy of Sulfur Speciation in Lithium-Sulfur Batteries
Authors: Wu Heng-Liang , Huff Laura A. , Gewirth Andrew A.
Published: February 2020

In this talk we report on our use of in-situ Raman spectroscopy and cyclic voltammetry to investigate the mechanism of sulfur reduction in lithium-sulfur battery slurry cathodes. Raman spectroscopy shows that long chain polysulfides (S8
2-) were formed via S8 ring opening in the first reduction process at ~2.4 V vs Li/Li+ and short chain polysulfides such as S4
2-, S4
-, S3
․
- and S2O4
2- were observed with continued discharge at ~2.3 V vs Li/Li+in the second reduction process. Elemental sulfur can be reformed in the end of the charge process. (1-4)

Rate constants obtained for the appearance and disappearance polysulfide species shows that short chain polysulfides are directly formed from S8 decomposition. The rate constants for S8 reappearance and polysulfide disappearance on charge were likewise similar, suggesting that polysulfide oxidation and reduction is quasi-reversible. The formation of polysulfide mixtures at partial discharge was found to be quite stable. We also examined the effect of CS2 addition on the sulfur reduction mechanism.  Electrochemical and Raman results show that CS2 stabilizes the S8
2-product and inhibits further discharge of the cell

References:

(1) Barchasz, C. et al., Anal. Chem. 2012, 84, 3973.

(2) Cuisinier, M. at al., J. Phys. Chem. Lett. 2013, 4, 3227.

(3) Yeon, J.-T. et al., J. Electrochem. Soc. 2012, 159, A130.

(4) Hagen, M. et al., J. Electrochem. Soc. 2013, 160, A1205.
Electrochemistry of Sodium Nonatitanates in Lithium and Sodium Ion Batteries
Authors: Shirpour Mona , Seshadri Dhruv , Doeff Marca
Published: February 2020

Sodium nonatitanate, NaTi3O6(OH)·2H2O, readily undergoes electrochemical sodium and lithium insertion reactions at unusually low potentials.[1] The lower average insertion potential and higher theoretical capacity (~300 mAh/g) suggest that it could be a higher energy density alternative to the well-known anode material Li4Ti5O12.[2-3] Titanates are also denser materials than graphite, so full utilization of titanates in a lithium-ion cell should lead to a somewhat higher energy density. This presents an intriguing possibility of using high-energy anodes based on titanate materials for lithium and sodium ion batteries, provided they could be developed further.

The presence of mobile sodium ions in the lithium ion system is undesirable from a performance and safety point of view. A recent NMR study [4] on composite electrodes derived from sodium nonatitante cycled in lithium cells showed evidence of in situ sodium plating during the discharge process. Our ex situ and in situ synchrotron XRD diffraction patterns [5] suggest that mobile sodium ions undergo ion-exchange with the electrolytic solution and/or are de-intercalate upon recharge, then subsequently are reduced to metallic sodium at the very low potentials encountered during later discharges. We show that a simple ion-exchange process prior to incorporation in electrochemical cells removes all sodium ions, producing the lithiated form of the material. The lithiated material performs similarly to sodium nonatitanate in lithium cells, although coulombic inefficiencies are somewhat higher (Figure 1). A comparison is made between the structure and electrochemical behavior of sodium nonatitanate and the lithiated analog in lithium cells.

References

1. M. Shirpour, J. Cabana, and M. Doeff, Energy & Environmental Science, 2013, 6(8), 2538-2547.

2. Z. Yang, D. Choi, S. Kerisit, K. M. Rosso, D. Wang, J. Zhang, G. Graff and J. Liu, Journal of Power Sources, 2009, 192, 588–598.

3. D. Deng, M. G. Kim, J. Y. Lee and J. Cho, Energy & Environmental Science, 2009, 2, 818–837.

4. Mallory Gobet, PhD thesis, Department of Physics and Astronomy, Hunter College of CUNY, New York, 2014.

5. D. Seshadri, M. Shirpour, M. Doeff, Journal of The Electrochemical Society, 2014, 162 (1) A1-A8.

Figure 1
Roles of Processing, Structural Defects and Ionic Conductivity in Electrochemical Performance of Na3MnCO3PO4 cathode Material
Authors: Wang Chuanlong , Kaduk James A , Shaw Leon
Published: February 2020

Na3MnCO3PO4 with a potential to deliver two-electron transfer reactions per formula via Mn2+/Mn3+ and Mn3+/Mn4+ redox reactions and a high theoretical capacity (191 mAh/g) can play an important role in Na-ion batteries. This study investigates the dependence of the electrochemical performance of Na3MnCO3PO4-based sodium-ion batteries on processing, structural defects and ionic conductivity. Na3MnCO3PO4 has been synthesized via hydrothermal process under various conditions with and without the subsequent high-energy ball milling. Particle sizes, structural defects and ionic conductivity have been studied as a function of processing conditions. It is found that structural defects have a strong influence on ionic conductivity, which in turn, affects the charge/discharge capacity of the Na3MnCO3PO4-based sodium-ion batteries. In contrast, particle size effect is small. These results provide guidelines for rational design and synthesis of high capacity Na3MnCO3PO4 for Na-ion batteries in the near future.
Evaluation of Si Based Composite Helices Used As Anodes in Lib
Authors: Polat Deniz Billur , Keles Ozgul
Published: February 2020

Films with helices made of various Cu-Si atomic ratios (10-90%, 20-80%, 30-70%) were fabricated by an ion-assisted glancing angle co-deposition technique. The effect of Cu/Si atomic ratios on the morphologies and the structures were studied by SEM and XRD. The use of those helices as anode materials in lithium ion batteries were evaluated by galvanostatic test results.

The SEM analyses demonstrated that during the co-evaporation an increase in Cu/Si atomic ratio decreased the thickness of the helices, increased the tilting angle and decreased the homogeneity in the thin film morphology. The best performance was achieved when 20%at. Cu containing SiCu helical shaped thin film is used as anode material.

Keywords: Anode, thin film, helices, ion assisted glancing angle depositon, electron beam.
A Study of the Mechanical Degradation Process of Silicon Electrode in the Lithium Ion Battery Cycling Operation
Authors: Xie Yuanyuan , Qiu Ming , Gao Xianfeng , Yuan Chirs
Published: February 2020

Huge volume change during the intercalation and de-intercalation process is a critical issue limiting the application of silicon material in current lithium ion batteries. In this study, a comprehensive multi-physics model is developed to investigate the stress/strain variation of silicon electrode prepared via metal-assisted chemical etching method in the battery charge-discharge operation. A corresponding experiment is carried out as the physical base. The modeling results are firstly compared with the first principle models and the experimental data. Then, extensive simulations are performed to elucidate the cycling induced local stress/strain variations and the complicated interaction mechanisms under different operation conditions. Besides, modeling study is also conducted to investigate the effect of etching process on the silicon electrode in the cycling.
Phase-Transition Mechanism Investigations in Monoclinic Li2FeSiO4 Orthosilicate Cathode
Authors: Lu Xia , Arthur Zachary , Wei Huijing , Chiu Hsien-Chieh , Chen Ning , Zhou Jigang , Reid Joel , Jiang De-Tong , Gauvin Raynald , Zaghib Karim , Demopoulos George P.
Published: February 2020

Lithium transition metal silicates Li2

M
SiO4 (
M
= Fe, Mn, Co,  etc.)1
, 2, well-known for their 2-Li theoretical capacity, draw increasingly more attention. In this text, we propose a hydrothermal method3
to obtain phase-pure nanoscale lithium iron silicate Li2FeSiO4 for probing its electrochemical performance as Li-ion battery cathode. Two types of Li2FeSiO4 crystals are prepared, namely low-temperature monoclinic phase and high-temperature orthorhombic phase and their electrochemical performance is found to be strongly structure-depended. As a result, the electrochemistry-structure relationships are systematically investigated using in-situ synchrotron XRD/XANES characterizations and first-principles calculations. The results demonstrate that there are obvious phase transitions for the metastable monoclinic Li2FeSiO4 electrode upon cycling4 and the Li ion has poor diffusion kinetics with activation energy of minimum 0.80 eV in both structures.  Furthermore the charge compensation mechanism is discussed by XANES and calculations in monoclinic Li2FeSiO4 structure for more than one Li extraction. All of these findings reveal some missing links in our fundamental comprehension of these materials and provide ideas for designing/obtaining improved silicate cathode materials.

References

1. Nyten, A., Abouimrane, A., Armand, M., Gustafsson, T. & Thomas, J. O. Electrochemical performance of Li2FeSiO4 as a new Li-battery cathode material. Electrochem. Commun.
7, 156-160, (2005).

2. Gummow, R. J., He, Y., Recent progress in the development of Li2MnSiO4 cathode materials. J. Power Sources,
253
, 253, 315-331 (2014).

3. Wei, H.J. et al. Synthesis and Characterization of Li2FeSiO4 as Candidate High-Capacity Li-ion Battery Cathode Material. 227th ECS Meeting, May 24-28 (2015), Chicago, Illinois, USA.

4. Xia Lu, Huijing Wei, Hsien-Chieh Chiu, Raynald Gauvin, Pierre Hovington, Abdelbast Guerfi, Karim Zaghib and George P. Demopoulos, Rate-dependent phase transitions in Li2FeSiO4 cathode nanocrystals, Sci. Re. in revision (2014).
Phase Field Simulation of Lithium Ion Diffusion in Solid Electrolyte Interface
Authors: Guan Pengjian , Liu Lin
Published: February 2020

Silicon materials have been recognized as one of the new electrode materials in the next generation of lithium ion batteries (LIBs) with high energy density and large specific capacity. However, there is still a significant limitation to use the silicon based composite electrodes since the fracture occurs as a result of the huge volume change and fast lithium diffusion during the electrochemical lithiation process. A stable solid electrolyte interface (SEI) can help prevent fraction. However, the lithium diffusion inside SEI layer is still not fully understood. In this study, we focus on two dimensions (2-D) lithium diffusion simulation inside SEI layer with considering its morphology evolution. Our previous research (1) has proven that SEI morphology evolution can be regarded as a solification process, and phase field method shows great advantage to deal with the solification problem. The phase field variable  is applied to simulate the SEI morphology evolution without tracking the multiple interfaces directly. The detailed chemistry of SEI species formation reaction has not been considered in the phase field modelling. The simulation assumes that SEI is composed of hydrocarbons, PEO-type oligomers, LiF, LixPFy, and LixPFyOz products based on the XPS experiments in the literature. We apply different formation contact angles to represent the different surface energy of different SEI specis. We are able to track different material species in SEI layer with defining the properties of each species for lithium diffusion simulation. In this work, a new model will be developed to simulate lithium diffusion during SEI growth and its morphology evolution based on our previous research and the computational method reported Han’s work (2). The concentration field can be regarded as a conserved property during the long-range diffusion. Therefore, the Cahn-Hilliard equations can be applied to formulate the phase transformations and description of diffusion inside the silicon based electrode. The chemical potential can be achieved by driving the total free energy equation. And the flux, which is assumed to be proportional to the gradient of the diffusion potential, can be presented by Fick’s Law. With the combination of the Cahn-Hilliard formulation and Fick’s Law, we are able to predict the lithium diffusion coefficient and lithium concentration distribution inside SEI layer. With the improvement of the current model, it is expected that the understanding on lithium diffusion inside SEI layer could be advanced to more accurately predict the fracture of silicon based composite electrodes during the electrochemical lithiation process. In addition, the developed model could be applied to other interface region problems and it has great potential to be extended to three-dimensions.

1.         P. Guan, X. Lin and L. Liu, ECS Transactions, 61, 29 (2014).

2.         B. C. Han, A. Van der Ven, D. Morgan and G. Ceder, Electrochimica Acta, 49, 4691 (2004).
In-Situ Scanning Tunneling Microscopy and Electrochemical Quartz Crystal Microbalance Studies of the SEI Formation on Graphite Electrodes
Authors: Seidl Lukas , Ma Jiwei , Martens Sladjana , Mostafa Ehab , Schneider Oliver , Stimming Ulrich
Published: February 2020

Electric vehicles and portable electronic devices depend on high performance energy storage technology like rechargeable Li ion batteries, whose successful operation requires high energy- and power-densities just as low cost, reliability, safety and long lifetime.1,2 The energy and power density of batteries, as well as their costs are mainly determined by the electrode materials, whereas safety, lifetime and efficiency are strongly affected by the properties of the Solid Electrolyte Interphase (SEI).3 In the past three decades research tried to deepen the understanding of the SEI by a large variety of experimental methods, ranging from basic electrochemistry over microscopic techniques to spectroscopic tools4. Questions regarding its formation mechanism, its morphological appearance and its chemical composition have been tackled, but there is still a lack of understanding on the molecular level.

In the mid-1990s M. Inaba et al. carried out a series of experiments about the SEI-formation on model graphite electrodes and the co-intercalation of Li+-ions together with their solvation shell  using Electrochemical Scanning Tunneling Microscopy (EC-STM).5 EC-STM is a very powerful technique for surface studies, since it offers the possibility to in-situ image molecular processes at the electrode/electrolyte interface. In the present study, the SEI-formation was examined in depth by in-situ EC-STM on highly oriented pyrolytic graphite (HOPG) model electrodes both in commercial Li+-ion battery electrolytes as well as alternative electrolyte systems (see Figure 1). In addition, the Electrochemical Quartz Crystal Microbalance technique (EQCM) as another in-situ method gave further insights into the SEI-formation. Both in-situ techniques provided valuable information about the electrochemical characteristics of this system, leading to better understanding of the formation mechanism and the morphological appearance of the SEI.

Figure 1. In-Situ EC-STM study of the SEI-formation on HOPG in 1M LiPF6 in EC/DMC electrolyte: The surface is imaged while the potential (line) is scanned from 2.0 V vs. Li/Li+ to 1 V, held at this potential, and scanned back to 2 V. The y-axis of the STM image is converted to a time scale to correlate changes in morphology to the applied potential

1M. Armand, J.-M. Tarascon, Nature, 451 (2008) 652

2J. B. Goodenough, J. Solid State Electrochem, 16 (2012) 2019

3P. B. Balbuena, Y. Wang, Imperial College Press (2004), ISBN 1-86094-362-4

4H. Tavassol, J.W. Buthker, G.A. Ferguson, L.A. Curtiss, A.A. Gewirth, J. Electrochem. Soc., 159 (2012) A730-A738.

5M. Inaba, Z. Siroma, A. Funabiki, Z. Ogumi, T. Abe, Y. Mizutani, M. Asano, Langmuir, 19 (1996) 1535

Figure 1
Silicon-Graphite Electrode Performance in Lithium Ion Batteries: From Coin Cells to 500 Mah-Pouch Cells
Authors: Polzin Bryant J , Trask Stephen E , Lu Wenquan , Jansen Andrew N.
Published: February 2020

Current lithium ion anode and cathode materials cannot meet the desired gravimetric and volumetric energy demands for hybrid electric vehicles (HEV), plug in hybrid electric vehicles (PHEV) and pure electric vehicles (EV).  One way to improve the performance of these systems is to develop a high energy anode material.  One system that has shown promise is the incorporation of silicon particles into the anode.  Silicon by itself can have capacities up to 3000 mAh/g.  While this value is impressive, there are a number of issues that present themselves when trying to use all of that capacity.

Argonne National Laboratory has taken up the task to create a silicon-based anode that could be used with the current lithium ion cathode materials to increase the gravimetric and volumetric energy of these systems.  The capacity target for this electrode was chosen to be between 600-800 mAh/g (active material).  By selecting this value, systems modeling has shown that this anode capacity matched with current cathode materials would produce the most cost effective and energy dense systems.

This presentation will first focus on some of the initial development of the anode formulation and processing issues encountered.  From there, coin cell data (Figure 1) will be presented on the anode formulation and then the presentation will conclude with xx3450 pouch cell data.  Qualitative and quantitative data will be examined for each of the sections.

As a final point, the silicon anode formulation has been made into a practical and usable electrode and matched to the Electrode Library which has been created by the Cell Analysis, Modeling, and Prototyping (CAMP) Facility.  The silicon based anode, graphite based anodes, and various cathodes are available in the Electrode Library for use in the battery research community.

 Acknowledgment:

Support from Peter Faguy and David Howell of the U.S. Department of Energy’s Office of Vehicle Technologies Program is gratefully acknowledged.  This work was performed under the auspices of the U.S. Department of Energy, Office of Vehicle Technologies, under Contract no.  DE-AC02-06CH11357

Figure 1
Role of 1, 3-Propane Sultone and Vinylene Carbonate in Solid Electrolyte Interface (SEI) Formation and Gas Generation
Authors: Lucht Brett L , Garsuch Arnd , Gasteiger Hubert A , Zhang Bo , Metzger Michael , Meini Stefano , Payne Martin , Solchenbach Sophie
Published: February 2020

The cycling performance, ex-situ surface analysis, and in-situ gas analysis of lithium ion batteries containing the widely used electrolyte additives VC and PS has been investigated.  All of the electrolytes have good cycling performance at 25°C.  However, the electrolytes containing additives have better discharge capacity retention and coulombic efficiency upon cycling at 55°C. Analysis of the differential capacity plots suggest that both VC and PS are reduced prior to the carbonates and alter the structure of the anode SEI.   Ex-situ surface analysis confirms structural differences of the anode SEI.  Electrodes cycled in the presence of PS contain lithium alkyl sulphonate (RSO3Li) on the surface of the anodes.  The presence of the lithium alkyl sulfonate leads to higher lithium ion conductivity of the anode SEI.  Electrodes cycled with added VC contain poly(VC) in the anode SEI.  The presence of the poly(VC) leads to improved stability of the SEI.  Anodes cycled with both VC and PS contain lithium alkyl sulphonate and poly(VC) which leads to an SEI with both high conductivity and high thermal stability. In-situ gas analysis shows that both additives, VC and PS, are able to reduce the ethylene evolution during SEI formation by nearly 70 %. The formation of poly(VC) for electrodes cycled in VC is accompanied by CO2 evolution. The presence of the lithium sulfonate for PS leads to a lower onset potential of ethylene evolution. For VC, the only gaseous byproduct during reduction is CO2, while PS shows no gaseous reduction products. The combination of both additives leads to a superposition of the described phenomena. The reduction of gas evolution during SEI formation would allow a faster and easier industrial formation procedure for Li-ion batteries.
A Study of e- Transport through Li2O2, the Main Discharge Product in the Li-O2 Battery
Authors: Knudsen Kristian Bastholm , Jensen Søren Højgaard , Luntz Alan C. , Hjelm Johan
Published: February 2020

In the field of energy storage devices the pursuit for cheap, high energy density, reliable secondary batteries is at the top of the agenda. The Li-O2battery is one of the possible technologies that, in theory, should be able to close the gap, which exists between the present state-of-the-art Li-ion technologies and the demand placed on batteries by technologies such as electrical vehicles [1].

     However, the Li-O2 battery still suffers greatly from high overpotentials during oxygen reduction and evolution reactions (discharge and charge, respectively), poor rechargeability, and decomposition of salts and solvents etc.  [2] [3]. In order to improve the electrochemical performance of the Li-O2batteries; it is crucial to understand the fundamental mechanisms that governs and limits the system during electrochemical operation.

     Here we present a redox probing study of the charge transfer across the deposition product lithium peroxide, Li2O2, using outer-sphere redox shuttles: cobaltocene, ferrocene, and decamethylferrocene. The change in heterogeneous electron transfer exchange rate as a function of the potential and the Li2O2 layer thickness (~state of charge) was determined using electrochemical impedance spectroscopy. The attenuation of the electron transfer exchange rate with film thickness is dependent on the probing potential, indicating that hole tunneling is the dominant process for charge transfer through Li2O2supporting previous work by Luntz et al. [4].

     Additionally, this work includes the determination of diffusion coefficients and concentrations of the redox shuttles and the superoxide ion, in a 1,2-dimethoxyethane based electrolyte.

References

[1]
S. A. Freunberger, P. G. Bruce, L. J. Hardwick et J.-M. Tarascon, «Li-O2 and Li-S batteries with high energy storage,» Nature Materials, vol. 11, pp. 19-29, 2012.

[2]
B. D. McCloskey, A. Valery, A. C. Luntz, S. R. Gowda, G. M. Wallraff, J. M. Garcia, T. Mori et L. E. Krupp, «Combining Accurate O2 and Li2O2 Assays to Separate Discharge and Charge stability Limitations in Nonaqueous Li-O2 Batteries,» J. Phys. Chem. Lett., vol. 4, pp. 2989-2993, 2013.

[3]
R. Younesi, M. Hahlin, F. Björefors, P. Johansson et K. Edström, «Li-O2 Battery Degradation by Lithium Peroxide (Li2O2): A Model Study,» Chem. Mater., vol. 25, pp. 77-84, 2013.

[4]
A. C. Luntz, V. Viswanathan, J. Voss, J. B. Varley, J. K. Nørskov, R. Scheffler and A. Speidel, "Tunneling and Polaron Charge Transport through Li2O2 in Li-O2 Batteries," J. Phys. Chem. Lett., vol. 4, pp. 3494-3499, 2013.
25mg NMR Studies of Mg-Ion Battery Materials
Authors: Proffit Danielle L. , Kim Chunjoong , Senguttuvan Premkuvar , Duffort Victor , Nazar Linda F , Cabana Jordi , Burrell Anthony K. , Vaughey John T. , Key Baris
Published: February 2020

Multivalent-ion chemistries such as Mg-ion are emerging as alternative battery systems to Li-ion. Current Mg-ion chemistries are limited to relatively low voltages and relatively low reversible specific capacities (1-2). Recent research on potential high voltage Mg-ion cathode materials and alternative anode materials such as transition metal oxides and metal alloys have highlighted the urgent need to understand structure activity relationships and insertion/intercalation phenomenon for development of such systems (3). Solid state NMR is a powerful tool to investigate local structure and insertion/intercalation phenomena, particularly for batteries as shown for Li-ion chemistries with 6Li and 7Li NMR (4, 5). However, the low natural abundance (10%) of the NMR active Mg isotope (25Mg), highly quadrupolar nuclear spin of 25Mg (spin 5/2) and very low gyromagnetic ratio (i.e 30.6 MHz Larmor frequency relative to 1H = 500 MHz) limits the effective use of 25Mg NMR for solid Mg-ion battery materials (6). In this work, despite the challenges of 25Mg NMR, our recent efforts to characterize Mg environments in cathode materials such as MgMn2O4 spinels, MgV2O5, in anode materials such as h-TiO2 and Mg-Sn alloys will be presented. Chemical magnesiation using dibutylmagnesium and preliminary electrochemical (de)mangesiation and the structral changes induced will be discussed. The results will summarize the effectiveness of the method in distinguishing side reactions or undesirable conversion reactions, including amorphous phases, from intercalation phenomenon.

References:          

1.             D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, and E. Levi, Nature,
407 (6805), 724-727 (2000).

2.             H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour, and D. Aurbach, Energ Environ Sci,
6 (8), 2265-2279 (2013).

3.             Magnesium Batteries 1 and 2, 224th Electrochemical Society Meeting, San Francisco CA, 2013

4.             C. P. Grey and N. Dupre, Chem. Rev. (Washington, DC, U. S.), 104, 4493 (2004).

5.             B. Key, R. Bhattacharyya, M. Morcrette, V. Seznec, J. M. Tarascon and C. P. Grey, Journal of the American Chemical Society, 131, 9239 (2009).

6.             R. Dupree and M. E. Smith, Journal of the Chemical Society-Chemical Communications, 1483 (1988).
Modeling the Si-Current Collector Interface in Li-Ion Battery
Authors: Wang Miao , Xiao Xinran
Published: February 2020

Si is a promising anode material for Li-ion batteries (LIB) due to its high energy density. Nevertheless, the large volume variation of Si during lithiation/delithiation cycles presents a great challenge to its structural integrity in LIBs. To this end, a wide variety of Si electrode designs have been attempted. It has been shown that reducing its size to nano scale can effectively prevent the fracture of the Si electrode itself. However, failure may still occur at interfacial regions between the Si electrode and other components such as the current collector due to deformation mismatch. The detached Si becomes isolated from the electronic pathway and hence the cell capacity degrades.

Understanding the deformation and stress-strain relationship at the Si-current collector interface is an important step in engineering durable, high capacity LIBs. In this work, a multiphysics microstructure-resolved model [1] was used to simulate the deformation of Si nanorods on a Ni substrate reported by Bella et al [2].  The Si was described by an elasto-plastic law with a finite strain formulation. The Li concentration dependence of the Young’s modulus and yield strength was considered. Ni was modeled as an elasto-plastic material. The interface between Si and Ni was modeled as a region with unique properties.

The results revealed that the interfacial properties not only affect the deformed shape of the Si nanorod and Ni substrate but also the stress triaxiality in the system.  To reproduce the deformation as in the experiment, a parameter study with different interfacial properties was carried out. The interfacial properties resulting in the best correlation with the experiment were identified. The microstructure-resolved model will then be used to investigate the structure design of LIBs with Si anode.

Wu, Wei, Xinran Xiao, Miao Wang, and Xiaosong Huang. “A Microstructural Resolved Model for the Stress Analysis of Lithium-Ion Batteries.” Journal of The Electrochemical Society 161, no. 5 (January 1, 2014): A803–A813.

Berla, Lucas A., Seok Woo Lee, Ill Ryu, Yi Cui, and William D. Nix. “Robustness of Amorphous Silicon during the Initial Lithiation/delithiation Cycle.” Journal of Power Sources 258 (July 15, 2014): 253–59.