bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent Progress in Blue Phosphors: From Non-Thermal Quenching to Highly Efficient Phosphor
Authors: Im Won Bin , Kim Yoon Hwa
Published: February 2020

In the present era of solid-state lighting, white light-emitting diodes (WLEDs) have received enormous attention as general lighting source due to its energy efficiency and environmental friendly technology. However, the current high power WLED faces serious challenge of luminescence loss of phosphor due to the generation of heat under operation and at elevated temperature known as thermal quenching. Therefore, it is highly desirable to find new phosphors with high efficiency and thermal stability.

Hence, our search for a new and efficient phosphor host, has led to the emergence of oxohalide/oxide host with very high PL and conversion efficiency. In this talk, some works from our laboratory on the recent progress in blue-emitting phosphors are summarized. In particular, new NASICON based blue-emitting phosphor shows negligible thermal quenching for WLED applications, which exhibited broad blue emission under near UV excitation and retains its luminescence at elevated temperature of 473 K. Also, some blue-emitting phosphors with their excellent optical properties are reported.1,2

References

[1] S. J. Gwak, P. Arunkumar, and W. B. Im, J. Phys. Chem. C, Vol.118, pp. 2686-2692, 2014.

[2] Y. H. Kim and W. B. Im, Opt. Lett., Vol.39, pp. 4887-4890, 2014.

Figure 1
Influence of the Starting Solution on the Growth and Morphology of Rare Earth-Doped Yttrium Oxide Spherical Particles By the Urea Precipitation Method
Authors: Silver Jack , Ireland Terry , Fern George Robert
Published: February 2020

Abstract

Since the start of this millennium, the need for amorphous submicron spherical rare earth element (REE) precursors that after subsequent heat treatment (~1000°C) forms crystalline REE-doped yttrium or gadolinium oxide (Y2O3:REE or Gd2O3:REE) phosphors has generated an active area of research.1  The original impetus was for a variety of display applications such as cathode ray tubes for high definition television and field emission devices.2  Later uses have included X-ray imaging and X–ray computed tomography (after converting these spherical REE phosphor particles to oxysulfide phosphor particles using sulfur and further heat treatment whereby they retained their former size and morphology).3  These spherical REE phosphor particles have the ability to close pack to form a thin emissive layer.2

These REE phosphor particles are produced via a urea homogeneous precipitation method and its modifications.  In this work REE nitrate stock solutions which yielded spherical REE-doped hydroxycarbonate precursor particles.1  It was assumed due to the ‘boring’ similarity of the chemical properties of REEs that all the spherical phosphor particles precipitated using different dopants would have identical particle sizes and spherical morphologies.  Our observations have found this not to be the case, and that their chemistry is much more interesting.  For example precipitated Y2O3:Eu spherical particles are larger than Y2O3:Tb precursor particles, this is also the case after annealing at 980°C where the original morphology is retained (see Figure 1).

Also, it has been found that highly viscous Y2O3:REE and Gd2O3:REE nitrate precursor solutions used for the preparation of three-dimensional photonic structures such as inverse photonic band gap crystals4 and bio-templates5vary in stability (non-precipitation) for each dopant.

The reason behind these findings will be discussed in terms of the pH of the precursor solutions, electron configuration, oxidation state (preferred) and stoichiometry.

Figure 1. Annealed spherical phosphor particles of (a) Y2O3:Eu and (b) Y2O3:Tb.

References

 

X. Jing, T. Ireland, C. Gibbons, D. Barber, J. Silver, A. Vecht, G. Fern, P. Trogwa, and D. Morton, J. Electrochem. Soc.,
146, 4654 (1999).

M. I. Martinez-Rubio, T. G. Ireland, G. R. Fern, J. Silver, and M. J. Snowden, Langmuir, 17, 7145 (2001).

G.R. Fern, T.G. Ireland, J. Silver, R. Withnall, A. Michette, C. McFaul and S. Pfauntsch, Nucl. Instr. Methods Phys Res.,
A600, 434 (2009).

J. Silver, T.G. Ireland and R. Withnall, J. Mater. Res., 19, 1656 (2004).

J. Silver, R. Withnall, T.G. Ireland, G.R. Fern and S. Zhang, Nanotechnology, 19, 095302 (2008).

Figure 1
Controlling Particle Size and Luminescence in Mn4+ Activated K2SiF6
Authors: Nammalwar Prasanth Kumar , Porob Digamber G , Hanumantha Ravi , Setlur Anant A , Murphy James
Published: February 2020

Narrow red emitters have attracted large attention within  white LED and backlit display world over the past few years.  This is partially due to renewed interest in red emitting phosphor, K2SiF6:Mn4+ (PFS).  Though, the material is known in literature for more than two decades, its application in white LEDs and display devices can be realized only after some of the key issues in the synthesis of these materials are addressed. In this paper, we discuss  synthesis, controlling particle size and luminescence properties  of Mn4+ doped K2SiF6. Manganese doped Potassium hexafluorosilicate  exists in  cubic  crystal structure with narrow PL emission with a main peak at 631nm with a FWHM of 2nm. Based on the type of application within display or general lighting, the particle size requirement for PFS varies. We have studied various parameters that can influence  particle growth during synthesis in order to obtain PFS of desirable particle size. In the current study we have used variety of anti-solvents (solvents that do not dissolve K2SiF6), including isopropyl alchohol(IPA), acetic acid, Dimethyl sulphoxide (DMSO), acetone, ethanol etc., to initiate crystallization.  By controlling quantity of anti-solvents and process of addition, we have shown better control on particle size distribution.  Further,  in this study we also discuss on influence of anti-solvents on luminescence properties and yield of PFS obtained.
Tuning the Luminescence Properties of Organometal Halide Perovskites for Light-Emitting Applications
Authors: Zhong Haizheng
Published: February 2020

Organometal halide perovskites are inexpensive materials with desirable characteristics of color-tunable and narrow-band emissions for lighting and display technology, but suffering from the low photoluminescence quantum yields at low excitation fluencies.2 We developed a ligand-assisted reprecipitation (LARP) strategy to fabricate CH3NH3PbX3 (X=Br, I, Cl) nanocrystals.3 By controlling their size and shape, we demonstrated the size- and shape- dependent photoluminescence properties. Especially, we obtain brightly-luminescent and color-tunable colloidal quantum dots with absolute quantum yield up to 70% at room temperature and low excitation fluencies. The comparisons between small sized CH3NH3PbBr3 quantum dots (average diameter 3.3 nm) and corresponding micrometer-sized bulk particles (2-8 μm) suggest that the intense increased photoluminescence quantum yield originates from the increase of exciton binding energy due to size reduction as well as proper chemical passivations of the Br rich surface. We further demonstrated the fabrication of prototype light-emitting devices, providing enhanced color quality for display technology.

[1] Shirasaki, Y.; Supran, G. J.; Bawendi, M. G.; Bulovic, V. Nat. Photon.
2013, 7, 13-23

[2] Stranks, S. D.; Burlakov, V. M.; Leijtens, T.; Ball, J. M.; Goriely, A.; Snaith, H. J. Phys. Rev. Appl.
2014, 2, 034007.

[3] Zhang, F.; Zhong, H. Z.; Chen, C.; Wu, X. G.; Hu, X. M.; Huang, H. L.; Han, J. B.; Zou, B. S.; Dong, Y. P. ACS Nano
2015, DOI: 10.1021/acsnano.5b01154
Upconversion Luminescence of HfO2 Phosphors Embedded into Polyester FILMS
Authors: Carmona S. , Mariscal B. L. , Hérnandez J. M. , Alarcón-Flores Gilberto , Murrieta H. , Falcony Ciro
Published: February 2020

Upconversion (UC) luminescence in powder hafnia (HfO2) doped with Er3+, Yb3+ and Li+ was studied under continuous wave excitation at 980 nm. Powder samples were prepared by the simple evaporation technique. The simple evaporation technique is an inexpensive and scalable technique to obtain powders with excellent properties. The technique works heating a chemical solution until its evaporation point to achieve a powder. A thermal treatment is practiced in this powder in order to eliminate any kind of remnant from precursor materials and/or achieve an appropriate crystalline structure if it is necessary. This powders were attached into polyester films by spin coating technique; spin coating process consists in supplying a small puddle of a liquid resin onto the center of a substrate and then spinning the substrate at high speed (between 3000 and 6500 rpm), centripetal acceleration will cause the resin to spread and eventually it covers the substrate leaving a thin film of resin on the substrate surface.

This powders and films were optical, structural and luminescent characterized using x-ray diffraction, electron microscopy, IR spectroscopy and UV-Vis. A study of the infrared to green and infrared to red UC processes was performed including the analysis of the spectral and the temporal behavior. The mechanisms contributing to the UC luminescence were identified as excited state absorption and energy transfer among rare earth ions. (x, y) coordinates of CIE diagrams are reported also.

Finally, it is important to sight, that this kind of phosphors attached at polymeric films could be eventually incorporated to solar cells in order to increase its nominal efficiency.

1. François Auzel, Upconversion and Anti-Stokes Processes with f and d Ions in Solids, Chemical Reviews 2004 104 (1), 139-174

2. S. Carmona-Téllez, G. Alarcón-Flores, A. Meza-Rocha, E. Zaleta-Alejandre, M. Aguilar-Futis, H. Murrieta S and C. Falcony, Polyethylene terephthalate thin films; a luminescence study, Optical Materials, 42, 2015, 99–105.
Optical and Thermal Management of Phosphor-Converted LEDs
Authors: Raukas Madis , Kelso John , Lenef Alan , Linkov Alexander , Tchoul Maxim
Published: February 2020

Phosphor conversion generates over 95% of the light source lumens and affects efficacy, spectral tuning and quality of Solid State Lighting (SSL) devices as much as the efficient generation of suitable primary light from the pumping semiconductor chips.  In SSL, a large number of applications such as low/mid-power distributed area illumination may not need the highest luminance sources that typically bring along most stringent requirements on materials, for example, as with high-brightness spotlights or automotive headlights. The cumulative efficiency of handling generated photons matters everywhere.  Basic properties of phosphors like refractive index and temperature-dependent quantum efficiency, in a series of physical processes and according to conditions surrounding the converter (for example optical scattering and reflection off of various interfaces, transmission and heat conductivity through materials), determine the overall amount of light being extracted and in use.  Modifying the light scattering, reflectance and transmission in different conversion media types and adding to it options for reducing the converter temperature has the cumulative effect that allows for optimizing the light generation process. Crucial to the overall efficiency are losses both from light recycled back into the LED, from various reflective surfaces, and weak volume absorption, including self-absorption of the phosphor emission.  The influence of these factors will be demonstrated through examples of thermal-optical modeling and actual measurements on specific packaging configurations for a range of forward currents If.  For example, advantages gained through controlling the scattering in ceramics versus powder-in-silicone and using thermally conductive materials will be elaborated.  The gains can be realized in either efficacy or luminous flux.
Electron Transport in Magnetic Nanomaterials for Sensing and Catalytic Applications
Authors: Krishnan Sadagopan , Premaratne Gayan , Sunday Trey , Matlock Ryan , Walgama Charuksha
Published: February 2020

Understanding the electrochemical and electrocatalytic properties of magnetic nanomaterials as immobilized films on surfaces holds significance in designing miniaturized sensors and volume efficient catalytic reactors. Additionally, incorporating metalloenzymes, known for high catalytic turnover, allows the design of novel electrochemical biosensors and green bioreactors. Applications of magnetite nanoparticles in the areas of highly sensitive biosensors, in vitro and in vivo studies, separation and preconcentration of analytes, and catalysis are emerging. One of our objectives is to understand the direct electron transfer and self-exchange phenomena in magnetite nanoparticle assemblies on electrodes, which can act as a reference system to study other redox active nanoscopic materials and long-range biological electron transfer processes. Our findings on this objective will be presented.

Acknowledgements: We are grateful for the financial support by the National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health under Award Number R15DK103386.
Reversibility of Ferri-Ferrocyanide Redox during in-Situ Soft X-Ray Spectroscopy
Authors: Risch Marcel , Stoerzinger Kelsey A. , Regier Tom Z. , Peak Derek , Nagy Sayed , Shao-Horn Yang
Published: February 2020

Ferri-ferrocyanide is a common facile redox couple in electrochemistry and related fields; select applications include charge storage in flow batteries, prevention of electrolyte decomposition in batteries, redox shuttling in dye-sensitized solar cells and photoanodes, as well as measuring charge transfer on catalytic surfaces. Ferri-ferrocyanide is also frequently employed as a standard to establish new steady-state and time-resolved in-situ spectroscopy methods. Despite the ubiquity of the ferri-ferrocyanide redox couple in diverse fields, discussion exists as to whether its kinetics may depend on the composition of both the electrode and electrolyte. Furthermore, ferri-ferrocyanide decomposes when exposed to ionizing radiation such as soft X-rays at a synchrotron, which may lead to electrodeposition on the electrode.

We studied the photochemical response of ferri-ferrocyanide to intense synchrotron radiation by in-situ X-ray absorption spectroscopy at the iron L edge. For photon flux densities above a defined threshold, precipitation of ferric (hydr)oxide from both ferricyanide and ferrocyanide solutions was clearly detectable. The formation of the precipitate was accelerated during cyclic voltammetry, which we probed by time-resolved in-operando X-ray absorption spectroscopy. The iron redox was completely inhibited in the probed volume after only two electrochemical cycles (70 min). Our study highlights the importance of considering both electrochemical and spectroscopic conditions when designing in-situ experiments that can shed light on charge transfer and chemistry of active sites in energy and health research.
Enrichment of Novel Electroactive Bacteria from Equatorial Climate Sediments Via Potentiostatic Growth and Subsequent Characterisation Via Metagenomics, Metatranscriptomics, Voltammetry and Electrochemical Impedance Spectroscopy
Authors: Doyle Lucinda Elizabeth , Yung Pui Yi , Wuertz Stefan , Williams Rohan Benjamin Hugh , Marsili Enrico
Published: February 2020

Electrochemically-active microorganisms couple the degradation of organic matter to the production of electricity via extracellular electron transfer. They are usually enriched from sediments via growth at certain potentials, either in microbial fuel cells or in potentiostat-controlled electrochemical cells. Despite the great microbial diversity of sediments from natural and man-made environments, most electrochemical enrichments select a small group of dissimilatory metal-reducing microorganisms.

In this study, we aim to enrich novel electrochemically-active strains in sediments from various equatorial environments. Sediment inocula from urban waterways and mangroves were tested in long-term enrichment experiments at controlled anodic potentials. In addition to the conventional voltamperometric characterisation, the biofilm formed at the working electrode was subjected to electrochemical impedance spectroscopy (EIS) over a wide range of potentials. EIS of the biofilms revealed several charge transfer routes at different potentials and with different characteristic times. Furthermore, EIS enabled monitoring of the long-term changes of the electroactive biofilm and quantification of the effect of biofilm accumulation on the conductivity of the biofilm/electrode interface. 

Electrochemical analysis was coupled to metagenomics and metatranscriptomics to reveal novel electrochemically-active microorganisms and to understand their charge-transfer mechanism. The understanding of the microbe/electrode interaction in the sediments will assist in controlling the dynamic of metal cycling in urban sediments. Furthermore, novel electrochemically-active microorganisms will find application in bioremediation and environmental sensing applications.
Naphthoquinone Derivatives As Low-Potential Electron Mediators of Fad-Dependent Glucose Dehydrogenase
Authors: Hickey David P , Milton Ross D , Abdellaoui Sofiene , Lim Koun , Tan Boxuan , Minteer Shelley D.
Published: February 2020

Flavin adenine dinucleotide-dependent glucose dehydrogenase (FAD-GDH) is rapidly emerging as an alternative glucose-oxidizing enzyme in enzymatic fuel cells (EFCs).  FAD-GDH has the benefit over its commonly used counterpart, glucose oxidase (GOx), of not undergoing the parasitic reduction of O2 to H2O2, which can be troublesome in EFC applications. Additionally, the FAD cofactor has a relatively low redox potential in comparison to heme-based and PQQ-dependent enzymes, which can allow for a much higher theoretical cell potential. However, FAD-GDH is unable to facilitate rapid rates of direct electron transfer, and therefore requires a low-overpotential redox mediator to take full advantage of the low oxidation potential of its FAD cofactor.

We have prepared a range of naphthoquinone analogues that are capable of mediating electron transfer between FAD-GDH and carbon electrodes, with onset potentials ranging between -0.425 to -0.150 V (vs. SCE), at pH 7.4. Several naphthoquinone derivatives were immobilized either onto a poly(ethylenimine) backbone or directly onto the outer shell of FAD-GDH to yield a naphthoquinone redox hydrogel and a naphthoquinone-labeled FAD-GDH. Both methods demonstrated large catalytic current densities at low onset potentials. When coupled with an O2-reducing biocathode (bilirubin oxidase, direct electron transfer-type) the glucose/O2 EFC possessed a large open-circuit potential (OCP) of 0.864 V and was able to deliver a maximum current density of 5.4 mA cm-2. The EFC reached its maximum power density (2.3 mW cm-2) at 0.55 V.
Synthesis of 3D Cos/CNF Electrode for Efficient Oxygen Evolution
Authors: Zhang Junfeng , Chen Rui , Liu Qi , Wang Qingfa
Published: February 2020

In order to achieve a high efficiency oxygen production, 3D electrode was designed and synthesized by electrodeposition of cobalt sulfides (CoS) onto the conductive carbon fiber paper (CFP) substrate (1×1 cm2) by cyclic voltammetry at different scan rate of 5, 10, 20, 30 mV s-1 in 12.5 mM Co(NO3)2 and 12.5 mM thiourea. The CoS/CFP was directly used as anode to highlight the merits of the novel architecture, showing a rather low Tafel slope (~60 mV dec-1) and low overpotential (~0.3 V). The high electrochemical performance of CoS/CFP electrode will be discussed in detail with the analysis of SEM, XRD and XPS.
Excellent Thermal Stability of VOPO4 As Cathode for Lithium-Ion Battery
Authors: Huang Yiqing , Lin Yuh-Chieh , Chung Youngmin , Chernova Natasha , Omenya Fredrick , Ong Shyue Ping , Whittingham M. Stanley
Published: February 2020

Lithium ion batteries are widely used in portable electronic devices and electric vehicles. However, safety is one of the most important issues for the Li-ion batteries’ use. Some cathode materials, such as LiCoO2, are thermally unstable in the charged state. Upon decomposition these cathode materials release O2, which could react with organic electrolyte, leading to a thermal runaway. Thus, the safety of the Li-ion battery depends on the interaction between the cathode materials and the organic electrolyte. In this work, we have investigated three types of cathode materials: layered oxide LiNi0.8Co0.15Al0.05O2 (NCA); olivine phosphates LiFePO4, Mn-rich LiFe1-yMnyPO4 (LMFP); and multielectron vanadyl phosphates VOPO4, LiVOPO4 and Li2VOPO4. The thermal behavior of the materials with and without electrolyte (1M LiPF6 in EC: DMC=1:1) was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis coupled with mass spectroscopy (TGA-MS). The solid products of the thermal reactions were further studied by x-ray diffraction. The results indicate that electrolyte decomposes between 250 ºC and 300 ºC, releasing 391 J/g heat (Fig.1 a). NCA (charged to 4.6 V) starts to decompose at 220 ºC, generating large amounts of O2 and 674 J/g heat without the electrolyte. When NCA is heated with the electrolyte, the heat released is close to 800 J/g (Fig.1 b), which could result in a thermal runaway of the battery. LMFP charged to 4.4 V (MFP) partially decomposes below 350 ºC and gives off 476 J/g heat in the presence of the electrolyte (Fig.1 c). On the other hand, VOPO4 and its lithiated compounds (LiVOPO4, Li2VOPO4) have the best thermal stability: the heat generated by any of them without electrolyte is less than 100 J/g when heated up to 350 ºC. In the presence of the electrolyte, the heat released is also significantly less than that of NCA and MFP (Fig.1 d). We will also present evidence from the first principles phase diagrams that support the experimental conclusions, including predicted O2 evolution temperatures and resulting phase equilibria. This work was supported as part of the NorthEast Center for Chemical Energy Storage (NECCES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0012583.

Figure 1
Liquid Catholyte Investigations for Safer Storage of a Li Primary Battery
Authors: Patrissi Charles J. , Schumacher Christian R.
Published: February 2020

The close proximity of the electrode materials is a design risk for commercial off the shelf (COTS) Li batteries.  COTS Li batteries can off gas and ignite if the electroactive materials are inadvertently mixed by events such as thermal abuse, crush, penetration, and shock.  Crew safety on US Navy ships and submarines critically depends on minimizing the probability of exposure to toxic gases and fire.  The Naval Undersea Warfare Center (NUWC) is investigating a primary Li battery design for undersea applications that is, in principle, safer to store and transport than COTS batteries.  In this approach a liquid catholyte is stored separately from a Li metal anode.  The catholyte is added to the anode housing immediately prior to off board deployment of the energy section.  With this configuration the electroactive materials can be stored separately and more safely than in COTS batteries.  NUWC has recently begun investigating slurry catholytes1 comprised of solid redox active cathode materials and electronically conductive carbon powders dispersed in a nonaqueous electrolyte.  Our goals are high volumetric charge capacity, high voltage, good power density and a “pumpable” rheology.  These properties are significantly affected by the formulation of the slurry such as the choice of redox active material, the volumetric solids concentration of the redox active and carbon materials, the interaction between the particles, and the particle size distributions.  This talk will discuss NUWC’s separated anode / catholyte battery concept, the tradeoffs of various electroactive cathode materials, and the results of catholyte investigations and their expected impact on the performance of a Li-slurry catholyte primary battery.     

1) M.Duduta., B.Ho, V.C. Wood, P. Limthongkul, V. E. Brunini, W. C. Carter, and Y-M Chiang,
Semi-Solid Lithium Rechargeable Flow Battery
, Adv. Energy Mater. 2011, 1, 511–516
Electroactive Polymer for Reversible Overcharge Protection in Lithium-Ion Batteries
Authors: Wang Bin , Cheng Jianli
Published: February 2020

Great improvement in the safety of lithium ion battery is needed to meet the full requirements of electric vehicles (EV).  Among these safety hazards, overcharge has long been recognized as a primary concern because it can lead to dangerous events such as thermal runaway, fire and explosion.  The electroactive polymer approach utilizes the unique electronic properties of the polymers to form a reversible resistive shunt between the current collectors and protect the cell from overcharging. The process is self-activated by voltage, and it does not pose interference during normal cell charge and discharge.

      In this work, we report the recent progress in cell overcharge protection for high-energy-density lithium ion batteries. By incorporating the reversible electroactive polymers into highly porous membrane separators, we demonstrate that the composites can provide reversible and stable overcharge protection for a variety of cell chemistries. The results for the protection of  Li1.05Mn1.95O4 or LiNi0.8Co0.15Al0.05O2 electrode will be discussed. Both cells were protected at a steady state voltage of 4.5 V for well over 100 cycles.

ACKNOWLEDGEMENTS

The authors would like to acknowledge the support from the Startup Foundation of China Academy of Engineering Physics, Institute of Chemical Materials (KJCX201301 and KJCX201306) and the Natural Science Foundation for Young Scientists of Sichuan province (No. 2014JY0202).

The authors would like to acknowledge the support from the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Freedom CAR and Vehicle Technologies of the U.S. Department of Energy under Contract No. DE-AC02- 05CH11231.
In Situ Diagnosis and Control of Li-Ion Batteries for Enhanced Safety
Authors: Zhang Guangsheng , Ge Shanhai , Xu Terrence , Wang Chao-Yang
Published: February 2020

Safety of Li-ion batteries remains a critical challenge due to their high energy density and use of flammable electrolyte. The challenge is further propelled by their ever-increasing and demanding applications in electric vehicles (EVs). Recent high-profile events involving electric cars and airplanes that employ Li-ion batteries as main or auxiliary power sources lend further urgency to enhanced Li-ion battery safety. 

We obtained insights of nonuniform temperature distributions in Li-ion battery cells through in situ diagnosis1. Inspired by those insights, we developed a reaction temperature sensing (RTS)-based control technique to enhance Li-ion battery safety. The RTS-based control is demonstrated to shut down an external short circuit event 3 times earlier than conventional surface temperature- based control and effectively prevent cell damage2.

We will apply the RTS-based control and in situ diagnosis of temperature distributions to other challenging safety scenarios including internal short circuit. The progress will be presented.

Reference

1. G. Zhang, L. Cao, S. Ge, C.Y. Wang, C. E. Shaffer, C. D. Rahn, In situ measurement of radial temperature distributions in cylindrical Li-ion cells, Journal of The Electrochemical Society,2014, 161 (10): A1499-A1507

2. G. Zhang, L. Cao, S. Ge, C. Y. Wang, C. E. Shaffer, C. D. Rahn, Reaction temperature sensing (RTS)-based control for Li-ion battery safety, Scientific Reports, under review
Probing Lithium-Ion Battery Safety in Mining Environments
Authors: Lipka Stephen M , Rogers Fon , Whitlow David Tyler , Bramel Taylor
Published: February 2020

Lithium-ion batteries are increasingly ubiquitous in portable consumer electronic devices, including laptop computers, cellular phones, and tablet computers. Lithium-ion batteries are also finding widespread deployment in many additional applications and settings, including underground mining environments, where lithium-ion batteries are used as electrochemical power sources for cap lamps, and in tracking and communications equipment.1,2 Battery safety is of paramount importance in any portable electronic device regardless of setting, and is particularly significant in enclosed and isolated areas such as passenger aircraft, or in underground mining environments, where potentially explosive methane/air mixtures can be ignited by a simple spark, which can be caused by shorting and thermal runaway of lithium-ion batteries.

This presentation will summarize systematic abuse testing of different lithium-ion batteries used in underground mining safety and communication equipment, including lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt oxide (NMC), and lithium iron phosphate (LiFePO4) based cathode chemistries. Prismatic and cylindrical 18650 lithium-ion batteries were obtained from commercial vendors and subjected to both wedge and flat plate crush tests, in order to determine the relative safety of each cathode chemistry under two crush speeds and various states-of-charge (SOC). Battery voltage, case temperature and applied load were recorded for each crush test. Video recording of each crush test was also collected.  In some cases, hard or soft electrical short circuits were caused by crushing the battery, resulting in thermal runaway, rapid temperature increases, and explosions or fires. Correlations will be drawn between choice of cathode chemistry, state-of-charge, type of crush test, and choice of atmosphere (air or methane/air mixtures), in order to determine the most suitable lithium-ion battery chemistry for underground mining applications.

References

1) Dubaniewicz, T. H. Jr.; DuCarme, J. P. Journal of Loss Prevention in the Process Industries.
2014, 32, 165.

2) Dubaniewicz, T. H. Jr.; DuCarme, J. P. IEEE Transactions on Industry Applications.
2013, 6, 2451-2460.
Integrated Multiscale Multiphysics Modeling of Dynamic Short Circuit Behavior in Large Lithium-Ion Batteries
Authors: Kim Gi-Heon , Yang Chuanbo , Pesaran Ahmad
Published: February 2020

Scale-up of the battery raises the complexity of interactions among the physicochemical processes occurring in intricate geometries across wide range time and length scales. The entangled interplays critically affect the performance, safety, and reliability of the batteries. Violent incidents reported for lithium-ion batteries (LIBs)  and consequent safety concerns are still the major hindrance for fast market penetration of LIB-powered electric drive vehicles. Most of safety incidents leading to a thermal runaway in lithium-ion batteries involve internal-short-circuit (ISC).

ISCs are caused either from a latent defect growing over time or from a sudden mechanical failure of internal cell structure that may occur during battery intrusion or crush. Puncture and crush response of a battery involves various aspects of physics. The Multiscale Multidomain (MSMD) model framework provides a modular architecture, facilitating flexible integration of multiphysics model components. At initial stage of an ISC, the faulted battery is electrochemically active. This is true even through a whole event if no severe consequence follows. As such, the electrochemical model is imperative to determine the battery dynamic response to short circuit. For an induced ISC, fault current and accompanied heat must be quantified properly in consideration of thermodynamic and kinetic factors, while capturing the electronic current pathways along the intricate LIB geometries. LIB component materials become thermally unstable under exposure to high temperatures. The abuse reaction kinetics model predicts the battery’s chemical responses. In this paper, we introduce an integrated multiphysics LIB safety response model built on the MSMD nonlinear multiscale multiphysics model framework, and apply the model to investigate electrical, thermal, chemical and electrochemical behaviors of large-format cells in various form factors while resolving dynamic evolution of internal short circuit.
(Keynote) Biofilm-Supported Redox-Polymer-Type Materials for Electrocatalytic Oxygen Reduction of Importance to Biosensing and Bioenergetics
Authors: Kulesza Pawel J
Published: February 2020

Unique properties of biofilms, which include possibility of extracellular electron transport, specific redox activity and capability to form stable polymeric or hydro-gel like microorganism aggregates adhering to common surfaces (including the glassy carbon electrode substrate), were explored here to form systems analogous to redox-polymer modified electrodes. Growth of biofilms was demonstrated with use of Yersinia enterocolitica, a robust Gram-negative rod-shaped bacteria known to be resistive to pH changes (4-10) and temperature variations (0-40oC). The dynamics of bioelectronic transfers originating from the presence of c-type cytochromes, i.e. heme-containing proteins within the biofilm, were further enhanced by introduction of multi-walled carbon nanotubes. Long-term stability of the biofim-based materials was achieved by impregnating them with porous but rigid conducting polymer, poly(3,4-ethylenodioxythiophene) or PEDOT. The fact that carbon nanotubes were derivatized with the carboxyl-group containing 4-(pyrrole-l-yl) benzoic acid facilitated the materials integrity through electrostatic attractive interactions between anionic carboxyl sites and positively charged domains of conducting polymer (PEDOT) structures. In neutral media, the biofilm-based composite (hybrid) matrices exhibited themselves electrocatalytic activity toward reduction of hydrogen peroxide (with possibility of sensing in the broad range of concentrations) and some activity during electroreduction of oxygen. By immobilization of additional catalytic (cobalt porphyrin) sites, a truly bifunctional electrocatalytic interface capable of significantly enhancing oxygen electroreduction currents was produced. Apparently, the reduction of oxygen (to hydrogen peroxide) was initiated at cobalt porphyrin centers and the further reaction (decomposition of hydrogen peroxide intermediate to water) was continued at c-cytochrome–containing biofilm matrix. These features are of importance to bioenergetics, i.e. to the development of cathodes for biofuel cells or biobatteries.
(Invited) Nanostructured Electroactive Polymers for Energy Storage and Biosensors Technologies
Authors: Shi Ye , Yu Guihua
Published: February 2020

Nanostructured materials become critically important in a wide range of applications from renewable energy, electronics, and photonics to medical and life science, because of their unusual physical/chemical properties due to confined dimensions of such materials. This talk will present a novel class of polymeric materials we developed recently: nanostructured electroactive polymer gels that are hierarchically porous, and structurally tunable in size, shape, composition, porosity and chemical interfaces. Given advantageous features such as intrinsic 3D nanostructured conducting framework, excellent electronic conductivity and electrochemical activity to store and transport ions, they have been demonstrated useful for a number of technological applications in energy, bioelectronics, and environmental devices. Several examples on developing next-generation energy storage and ultrasensitive biosensors devices will be discussed to illustrate ‘structure-derived functions’ of this special class of materials.
(Invited) Intermediate Tunnelling-Hopping Regime in DNA Charge Transport
Authors: Xiang Limin , Palma Julio , Bruot Christopher , Mujica Vladimiro , Ratner Mark A , Tao Nongjian
Published: February 2020

Charge transport in molecular systems, including DNA, is related to many basic chemical and biological processes, and critical to device applications with molecules. This important phenomenon is often described as either coherent tunneling over a short distance or incoherent hopping over a long distance. Here we show evidence of an intermediate regime where coherent and incoherent processes coexist in dsDNA. We measure charge transport in single DNA molecules bridged to two electrodes as a function of DNA sequence and length. The resistance of DNA in general increases linearly with length, as expected for incoherent hopping. However, for DNA sequences with stacked guanine-cytosine (GC) base pairs, a periodic oscillation superimposes on the linear length dependence, indicating partial coherent transport. The result is supported by the finding of strong delocalization of the highest occupied molecular orbitals of GC by theoretical simulation and modeled based on the Büttiker theory of partial coherent charge transport.
(Invited) Functional Conductive Polymer Binders for High-Performance Silicon-Based Anodes in Lithium-Ion Batteries
Authors: Jia Zhe , Zhao Hui , Liu Gao
Published: February 2020

Electrode design has been a key aspect to achieve the high energy and power density, and superb cycling performance. Current lithium-ion-batteries (LIBs) use intercalation materials such as LiCoO2 for the cathode and graphite for the anode, with a theoretical specific capacity of around 370 mAh/g. Si, with rich natural abundance, exhibits theoretically 10 times higher capacity (4200 mAh/g) than the graphite (370 mAh/g). However, the problem associated with Si-based materials is that they involve a large volume change during cycling,and poor electronic conductivity. Fully alloying Si on charge to form Li4Si results in an almost 300% volume increase. Because of this high volume change, the electronic integrity of the composite electrode is disrupted, and a high and continuous surface side reaction is induced, both leading to a drastic capacity fade.

Our state-of-the-art electrode materials design has made a big step forward to use a polymer binder to ensure the integrity of the composite electrode for a dimensionally stable laminate. The polymer binder plays a critical function in maintaining mechanical stability and electrical conduction during the lithium insertion and removal process. We proposed a specific designed conductive polymer structure to provide molecular-level electronic connections between the active material and the conductive polymer matrix. Not only cycling stability of the silicon is significantly enhanced, being conductive itself, the use of conductive polymer binder eliminates the necessity of conductive additive, which considerably increases the loading of active material.

This approach achieves unparalleled capacity retention during cycling. An underlying principle to use conductive polymer as a negative electrode binder was developed and implemented in the synthesis of the new conductive and adhesive binders Poly(9,9-dioctylfluorene-co-fluorenone-co-methylbenzoic ester) (PFFOMB). These binders are cathodically (reduction) doped in the Si electrode environment to achieve electrical conductivity. Adhesion groups have been incorporated into the polymer binder to improve the electrode’s integrity. Aldrich commercial nano-Si powder has been used with the conductive polymer binder to form a Si electrode, without the need for acetylene black conductive additive. The electrode demonstrated over 650 cycles between 1volt (V) and 0.01 V at the 2500 milliamp hours per gram (mAh/g)-Si with only 20% capacity fade (Fig. 1). The conductive polymer binders have opened a new paradigm of electrode design for Si materials: they provide molecular-level electrical interaction between the electrode matrix and active materials and accommodate volume expansion of high-capacity Si materials.

Figure 1
Spectroelectrochemical Studies of Charge Transfer Processes in Stable Nitroxyl Radical-Containing Polymers
Authors: Hughes Barbara Katherine , Braunecker Wade A. , Johnson Justin C. , Gennett Thomas
Published: February 2020

The electrochemical redox reaction of stable organic polymer materials with unpaired electrons is a relatively new and exciting area of battery research.  Specifically, stable nitroxyl radical-containing polymers have displayed excellent characteristics as the cathode-active material and have presented themselves as a low-cost and environmentally friendly alternative to the current Li-ion battery technologies. However, with the advancement of organic-radical battery technology there is a lack of fundamental understanding of the dynamics of charge transfer processes, electronic and ionic, within organic radical-containing polymers.  In order to elucidate these mechanisms further, we have conducted extensive spectroscopic and spectroelectrochemical investigations of macromolecular systems containing nitroxide radicals.

We have employed potential modulated spectroelectrochemical techniques for our study of stable radical polymer systems whereby, kinetic information can be determined, specifically rates of charge transfer and ion diffusion within our polymer systems. A key factor determining the success of such experiments is that the material of interest exhibits a strong absorption coefficient and allows for measurement in the concentration regime conducive for electrochemical studies (typically up to 10 mM).  For this reason, of the available stable nitroxyl radical systems, we have chosen first to study the oxidation of a nitronyl nitroxide derivative. To simulate an electrode architecture, spectroelectrochemical studies were performed in the solid state, and the efficacy of charge transfer was investigated as a function of film thickness, counter-ion size, and radical polymer composition. As we have developed a synthetic process to produce ordered systems of stable organic radicals in the form of fixed polymer brushes grown from transparent conducting substrates, the effects of nano- and mesoscale ordering of the polymer film on charge transfer dynamics will also be presented.
Conjugated Organophosphorus Materials As Electrodes for Organic Batteries
Authors: Reus Christian , Baumgartner Thomas
Published: February 2020

The demand for environmentally benign, organic π-conjugated materials is constantly growing since they combine low cost and solution processability with light weight and mechanical flexibility. These features open up the opportunity to access new domains in contemporary organic electronics such as rechargeable organic batteries. The currently best established batteries are based on Li-ion technology and typically suffer from various disadvantages, for example (i) the use of expensive and toxic metal oxides (e.g. LiCoO2), (ii) slow kinetics of electrode reactions leading to extended charging times, and (iii) the danger of self-ignition resulting from heat generation during the Li-intercalation processes at the electrodes. To overcome these deficiencies, research is focused on the development of electrochemically active compounds for use in ‘plastic’ batteries. State-of-the-art organic electrodes feature well-known redox-active structural motifs that exhibit stable reduced or oxidized states, such as nitroxides,[1] quinones,[2] or viologens[3] (e.g., N,N’-dimethylviologen MV2+
; cf. Figure).

Recent research in the area of π-conjugated materials has shown that the incorporation of inorganic main group elements – in particular B, Si, and P – is an efficient strategy to obtain materials with intriguing properties for a host of most different practical applications.[4] Our group has of late designed new π-conjugated, ring-fused organophosphorus viologens such as the N,N’-dimethyl-2,7-diazadibenzophosphole oxide (phospha-MV2+
, cf. Figure) that show enhanced electronic characteristics for potential battery applications as compared to parent viologen MV2+
.[5] The materials’ properties of these compounds have been refined by further modifications of phospa-MV2+
in order to improve the applicability in cathodes and/or anodes. Half-cell cycling studies of fabricated electrodes against lithium metal shed light on the performance of the electrode materials with respect to their capacities under different C-rates for charging/discharging currents, cycle lives, and other performance criteria.

References

[1] Nishide, H.; Oyaizu, K. Science
2008, 319, 737-738.

[2] Zhu, Z.; Hong, M.; Guo, D.; Shi, J.; Tao, Z.; Chen, J. J. Am. Chem. Soc. 2014, 136, 16461-16464

[3] Sen, S.; Saraidaridis, J.; Kim, S. Y.; Palmore, G. T. R. ACS Appl.
Mater. Interfaces 2013, 5, 7825-7830.

[4] He, X.-M.; Baumgartner, T. RSC Adv.
2013, 3, 11334-11350.

[5] Durben, S.; Baumgartner, T. Angew. Chem. Int. Ed.
2011, 50, 7948-7952.

Figure 1
Modeling Multi-Scale Carbon Fiber Supports for Thin Film Bioelectrodes
Authors: Do Duyen Van Thuy , Wen Hao , Gumeci Cenk , Calabrese Barton Scott
Published: February 2020

Carbon electrodes with their super electro-catalytic properties are commonly used in electrochemistry, especially in biomolecular redox reactions1. Electrospinning as a low cost, facile technique is applied to produce uniform carbon nanofibers between 150 nm and 1µm fiber diameter by pyrolyzing electrospun Polyacrylonitrile (PAN) fiber at 250°C and 1100°C. Varying the concentration of PAN in N,N-Dimethylformamide precursor solution changes the fiber diameter and leads to diversity in materials properties, such as surface area, void fraction and conductivity. These electrospun carbon nano fiber (ECNF) properties are characterized by SEM, BET, and four-point probe resistivity measurements.

 Thin film Os+/2+ mediated electron in hydrogel immobilized glucose oxidase layer is coated on either single micro fiber 2 or free - standing carbon nanofiber mats (Figure 1) to study the effect of carbon fiber physical properties on electron transfer in mediated redox hydrogel bioanode. Electron transport via redox polymer Os+/2+ is enhanced by reducing the average hydrogel film thickness with uniform distribution of small fiber of high surface area (<1.6E3 cm-1 surface area per volume). A transport model is developed to give more insight into these correlations and yield more understanding of electron transfer mechanism in thin film porous electrode.

Figure 1
Insights from the Rigid-Band Model: Tuning Perovskite Electronic Structure for the Oxygen Evolution Reaction
Authors: Hong Wesley T , Stoerzinger Kelsey A. , Grimaud Alexis , Lee Yueh-Lin , Yang Wanli , Shao-Horn Yang
Published: February 2020

Transition metal oxides exhibit a rich and diverse range of chemistries and physics that has long established their application in a number of electrochemical energy conversion and storage technologies. The ability to design oxides expressly tuned for these applications is rooted in fundamental understanding of the relationships between structure, chemical composition, electronic properties, and electrochemical functionality. In particular, the perovskite family has been a central focus for studying oxygen evolution reaction (OER) electrocatalyst design due to its chemical flexibility and diverse electronic properties. In this work, we probed the valence electronic states for various first-row transition metal perovskite OER catalysts with a range of activities, using combined analysis of X-ray emission, absorption, and photoelectron spectroscopy (XES, XAS, XPS). We examined major compositional design approaches to better understand how to tune perovskite electronic structure – specifically A- and B-site substitutions, oxygen vacancy content, and the double perovskite family. Through these studies, we find clear principles for tuning the metal-oxygen bond strength and identify guiding insights for controlling the mechanism and kinetics on different perovskite surfaces.