bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling and Lifetime Assessment of Lithium-Ion Batteries Used for Solar Firming Applications and Grid Storage
Authors: Lawder Matthew T , Northrop Paul W. C. , Subramanian Venkat R.
Published: February 2020

The intermittent nature of many renewable power sources inhibits their implementation in the electric grid (1). Consumers demand an uninterrupted power supply and the unpredictable nature of renewables means that only a portion of the electric grid’s energy portfolio can come from these sources. However adding an energy storage device to renewable power sources can stabilize the source’s intermittency.

A coupled system can supply a constant level of power to the grid (below the system’s peak generation rating) by storing part of the energy created during peak generation hours and releasing that energy during periods of low or no power generation (see figure 1).

Our study utilizes a model of a photovoltaic solar cell coupled with a Lithium-ion battery. The system charges the battery anytime power generation exceeds the goal constant output and discharges the battery when the solar power output falls below the goal output. This protocol will control the system with the goal of generating the highest constant power output while still protecting the battery from degradation. Stabilizing the power source inevitably leads to sub-optimal charging and discharging patterns for the Li-ion battery and additionally can lead to intermittent cycling (small depth of discharge or small charging percentages). Our control strategy will seek to optimize both systems for single cycle and lifetime results.

The hybrid system will involve an electrochemical and transport based Li-ion battery model (2-5). Intermittent charging patterns obtained from solar insolation variations will be studied and their effects on capacity fade will be analyzed. The study will focus on the lifetime benefit that can be obtained from a battery during implementation into a solar firming application and seeks to understand the dynamics associated with coupled solar-battery system.

Acknowledgements

The authors acknowledge financial support from the U.S. Department of Energy’s Advanced Research Projects Agency- Energy (ARPA-E), and the Solar Energy Research Institute in India and the United States (SERIIUS), as well as, Washington University in St. Louis’ McDonnell Academy Global Energy and Environmental Partnership (MAGEEP)

References

1. Gopstein, A. M. Proceedings of the IEEE.,
100:2, 311 (2012).

2. Santhanagopalan, S., Guo, Q., Ramadass, P., and White, R. E. . J. of Power Sources., 156, 620 (2006).

3. Doyle, M., Fuller, T. F., and Newman, J. J. of the Electrochemical Society., 140, 1526 (1993).

4. Fuller, T. F., Doyle, M., and Newman, J. J. of the Electrochemical Society., 141,1 (1994).

5. Northrop, P. W. C., Ramadesigan, V., De, S., and Subramanian, V. R. J. of the Electrochemical Society., 158, A1461 (2011).
Hybrid Energy Storage System for Stationary Applications
Authors: Zhuk Andrey Zinovievich , Denshchikov Konstantin Konstantinovich , Fortov Vladimir Evgenievich , Sheindlin Alexander Efimovich
Published: February 2020

Energy storage systems have a wide spectrum of functions. They must provide power quality, shaving of load change, matching in distributed power systems, bulk energy storage, and end-user reliability, e.g., uninterrupted power supply. Storage devices based on high-capacity batteries have a number of advantages: i) modular design and relatively compact size; ii) functional flexibility; iii) easy control and maintenance; iv) simple integration into Smart Grids. It is also well known that batteries have a number of unsolved problems, e.g.: i) high specific cost of stored energy; ii) insufficient cycle life (500 – 3 000 charge/discharge cycles); iii) significant decrease of cycle life at high charge/discharge current; iv) problem of depth discharge.

To solve the above mentioned problems, we propose the Hybrid Energy Storage system (HESS) incorporating supercapacitors in addition to batteries. Cost analysis of electrochemical storage systems based on batteries of different types, supercapacitors and their combination has also been carried out.

To verify the main principles of the proposal, we have designed and developed a HESS prototype. The main functional characteristics of the developed HESS were studied experimentally.

The prototype bases on Li-ion batteries and supercapacitors. Such energy storage system includes three main components: Li-ion batteries, supercapacitors, and grid interconnection consisting of two invertors and control and monitoring system. Energy storage capacity of developed HESS prototype is 100 kWh, nominal power—100 kW, peak power—200 kW. HESS was created and tested within the experimental facility including 1.5 MW gas turbine power plant, 200 kW controllable active and reactive loads, and a control and measurement system.

Experimental results showed that HESS successfully provides the following functions: (i) suppression of voltage, current, and frequency disturbances in the grid; (ii) compensation of reactive power in the circuit; (iii) uninterrupted power supply. In comparison with battery storage system without supercapacitors, HESS shows lower cost, and higher peak power. In hybrid energy storage system the presence of supercapacitors allows to shave peaks of power at the charge and discharge mode of the battery.

We believe that this feature of HESS will prolong the life time of batteries and thus increase the life time and reliability of the entire system.
A Radical Approach to Development of a Non-Aqueous Redox Flow Battery
Authors: Aaron Douglas , Delnick Frank , Sun Che-Nan , Nanda Jagjit , Zawodzinski Thomas A.
Published: February 2020

The future of renewable energy, due to its inherent variability, will rest on the capacity of the electrical grid to reconcile power production and consumption. Electrical energy storage can take many forms, one of which is the redox flow battery (RFB), which boasts some unique advantages over other storage technologies. Non-aqueous RFBs, while far less developed than aqueous chemistries, may possess benefits over aqueous RFBs including higher voltage and greater energy density.

The electrochemistry of a series of anion radicals for possible use in flow batteries is reported. The solvent utilized in this work is tetra(ethyleneglycol) dimethylether (TEGDME) and was chosen due to its very large voltage window (~4 V vs. lithium) and capability of dissolving large concentrations of aromatic compounds. An appropriate triflate salt (sodium or lithium) was added to the TEGDME to improve conductivity, facilitating electrochemical measurements. After removing as much of the impurities as possible, TEGDME with triflate salt served as a stable electrolyte with nearly no observable electrochemical reactivity. Anion radicals were formed by simply adding sodium or lithium metal to various aromatics dissolved in TEGDME and triflate salt.

The aromatics considered in this work covered a range of complexity, from biphenyl and naphthalene up to large compounds such as coronene. Our initial screening found that the redox potentials of the aromatic-anion radical couples also spanned a large redox potential range. Some were highly reversible and some were quite unsuitable for a RFB due to irreversible redox behavior. Sodium- and lithium-generated anion radicals behaved similarly, with the sodium-generated radicals exhibiting generally more favorable redox behavior (larger current and better reversibility). In addition, many compounds also formed dianions, allowing for greater potential range and energy density for that material.

Ultimately, the goal is to develop a non-aqueous RFB. Initial tests to screen materials and improve cell design using the biphenyl-anion radical for the negative side are in progress. Capitalizing on the benefits of this non-aqueous RFB chemistry could result in lower overall system cost for electrical energy storage compared to other technologies.

Acknowledgement: We gratefully acknowledge the support of Dr. Imre Gyuk and the US DoE Office of Electricity for support of this work. CNS and JN acknowledge Laboratory Direct Research and Development (LDRD) seed funding for this work.
(Invited) Carrier Dynamics and Photon Management for Improvement in Quantum Efficiencies of GaN-Based Visible Light-Emitting Diodes
Authors: Ryou Jae-Hyun , Kim Jeomoh , Choi Suk , Kim Hee Jin , Lochner Zachary , Ji Mi-Hee , Satter Md. Mahbub , Detchprohm Theeradetch , Yoder P. Douglas , Dupuis Russell D , Asadirad Mojtaba , Liu Jianping , Kim Jin Soo , Fischer Alec , Juday Reid , Ponce Fernando , Kwon Min-Ki , Yuan Dajun , Guo Rui , Das Suman
Published: February 2020

Data and analysis are presented employing several new methods to address carrier dynamics and photon management issues in order to improve internal quantum efficiency (IQE) and light-extraction efficiency (LEE) of GaN-based light-emitting diodes (LEDs). First, the roles of a new InAlN electron blocking layer (EBL) and hole transport among quantum wells (QWs) are discussed with a focus on the mitigation of efficiency droop at high current densities. While the origins of the efficiency droop remain to be controversial, currently suggested origins are all associated with carrier dynamics: the effect of the electron leakage being related to carrier confinement; hole transport to active region being pertinent to carrier injection and concentration in each QW, and Auger recombination becoming more dominant with increasing carrier density in each QW. The strategy for the improvement, therefore, includes (1) confining electrons in the active region as much as possible, (2) injecting holes into the active region as much as possible, (3) distributing the both carriers among QWs as uniformly as possible. In order to implement the strategies, we especially studied EBLs and hole injection and transport in the multiple QW (MQW) active region. The effects of the various EBLs on the efficiency droop was compared (Figure 1), showing the lowest efficiency droop ratio of ~18% for the LEDs with InAlN EBL due to better electron confining/blocking effect than the standard EBLs. Hole injection (into active region) and transport (across MQWs) are as important as electron confinement. Also, they are not inter-related. Uniform distributions of electrons and holes with the same concentration in each QW are a goal to effectively mitigate the efficiency droop. Whereas the uniform distribution of electrons among QWs is achieved without difficulties, that of hole is quite challenging. We employed triple-wavelength-emitting MQWs with different bandgap energies for the experimental evaluation of the hole distribution among MQWs (Figure 2), showing hole transport and resulting distribution of holes can be engineered by p-type layers. Secondly, new way of surface patterning is demonstrated. The periodic surface patterns having 2-dimensional hexagonal array were directly achieved by three-beam interference laser ablation technique without photolithography processes (Figure 3), resulting in improvement of LEE by ~20%. This new direct laser patterning also maintained ohmic behavior of contacts on p-type surface, unlike the case of the patterning using plasma dry etching.
Superatmospheric MOCVD Growth of Bulk InGaN for Template and Optoelectronic Applications
Authors: Conway Matthew , Deguzman Panfilo C , Stokes E. B.
Published: February 2020

InGaN, a III-Nitride wide bandgap semiconductor with theoretical bandgaps ranging between 0.7 eV (InN) and 3.39 (GaN), covers the entire visible spectrum and the near IR and UV. This makes InGaN an important material for photonic applications, including LEDs, laser diodes, and possibly solar cells.

To obtain smaller bandgaps within the material, more indium must be incorporated into the crystal. However, the differing chemical properties of indium and gallium, along with the limitations presented by the precursors, make indium incorporation beyond ~20% difficult to achieve, while maintaining high crystal quality. Work by Cheng Li et.al. indicates that photoluminescent intensity improves at higher pressure growths (still subatmospheric). Basic thermodynamics indicate that the temperature can be increased during growth at increased growth pressures, allowing an increase in process space. Also, that material stability can be improved by increasing the pressure during growth of InGaN.

A superatmospheric metal-organic chemical vapor deposition (MOCVD) reactor was designed and fabricated at UNC Charlotte to investigate the superatmospheric growth of InGaN, especially for growing high indium content InGaN. This reactor was designed to minimize gas phase reactions and to sustain smooth precursor flow while under superatmospheric conditions, solving one of the main problems with superatmospheric growth.

Experiments were done to obtain recipes for initial growths. This included finding critical thicknesses for InGaN of a set composition on GaN templates, V:III ratio experiments, estimating nitrogen vacancies by comparing elemental percentages from the EDAX results, optimizing growth temperatures, and flows for epitaxial growth.

Bulk InGaN was grown on Al2O3 and on n-type GaN templates. Early growths of InGaN on Al2O3 showed absorption below the GaN bandgap, with absorption starting around 2.4eV (~516nm) [figure]. Indium deposition was confirmed through EDAX results. X-ray diffraction results will be included in full paper, indicating phase and composition results. Early results grown on Al2O3did not show high intensity room temperature photoluminescence, although it could be detected with a spectrometer. However, the early photoluminescence results corresponded with absorption results, indicating that they were accurate.

InGaN was also grown on n-type GaN substrates, which were also grown by MOCVD and donated by VEECO. Greater photoluminescence was measured from early growths on GaN templates with the same recipes, presumably because the crystalline quality was increased by growing on a smooth, relaxed substrate, with a closer lattice match. Growth conditions, rates, and results will be discussed, along with any conclusions about the effects and capabilities of superatmospheric growth on parameters of bulk InGaN.
(Invited) Photon Management Using Si Nanocrystals and Er3+ Ions: Generation of Hot Carries upon Absorption of Low-Energy Photons
Authors: de Jong Elinore M.L.D. , Saeed Saba , Gregorkiewicz Tom
Published: February 2020

The most important limitation for efficiency of photovoltaic energy conversion appears due to the enormous mismatch between the broad-band character of the solar radiation and the discrete operation mode of solar devices, as determined by the specific bandgap energy of the active medium. One remedy for that would be the spectral transformation of the solar radiation before it enters a photovoltaic device. Specifically, such a “solar shaper” should split the large energy photons into smaller ones, whose conversion efficiency is optimal.

In my presentation, I will discuss how shaping of the solar spectrum can be achieved using layers of Si nanocrystals with and without Er doping. In such systems efficient photon transformation can be realized by quantum cutting [1] and/or emission from Er3+ ions sensitized by Si nanocrystals [2]. Also the recently identified [3] ultra-efficient colloidal Si nanocrystals can be used for the purpose. I will present evaluation of external quantum efficiency of emission from thin layers of Si nanocrystals in SiO2 and its evolution upon introduction of Er3+ ions. Using differently prepared materials I will evaluate how this can be maximized. I will also discuss energy efficiency of solar shapers based on Si nanocrystals and Er3+ ions.

[1] M.T. Trinh et al., Nature Photonics 6, 316-321 (2012).

[2] S. Saeed et al., under consideration

[3] K. Dohnalova et al., Light: Science and Applications 2, e47 (2013)
Tb3+ Luminescence in a-SiNx:H
Authors: Bosco Giacomo Ferreira , Tessler Leandro R.
Published: February 2020

Terbium doped hydrogenated amorphous silicon nitride was prepared by reactive sputtering from a silicon target partially covered with metallic Tb platelets in a Ar+N2+H2 atmosphere. When the samples have a high enough bandgap they present characteristic Tb3+ luminescence at 545, 585 and 620nm. This luminescence can be excited by an Ar+ laser either resonantly using the 488nm line which corresponds to the 490nm transition of the Tb3+ or via the a-SiNx:H network using the 476nm line. The samples were annealed at 300, 400 and 500°C. For non-resonant excitation, the dependence of the Tb3+ luminescence intensity with the annealing temperature depends on the hydrogen content for a given nitrogen content.The resonant luminescence intensity almost does not depend on the annealing. The luminescence intensity under non-resonant excitation decreases exponentially with the temperature. Surprisingly, under resonant excitation the luminescence intensity increases slightly with the temperature. These results are intepreted as due to very effective intra-4f radiative recombination processes in Tb3+ in a-SiNx:H. However, the excitation transfer from the matrix decreases with temperature probably due tophonon induced non-radiative recombination of carriers in the a-SiNx:H network.
Corrosion Inhibition Efficiency on X65 Steel of Single Surfactant and Mixtures of Alkyl Benzyl Dimethyl Ammonium Chlorides
Authors: Zhu Yakun
Published: February 2020

The corrosion inhibition on X65 steel of a series of single and mixtures of surfactants, alkyl benzyl dimethyl ammonium (CnBDMAC) chloride surfactants, was studied. The surfactant properties were studied by surface tension measurement, optical spectrometry, and Gaussian simulations/calculations. The surface tension was measured to determine critical micelle concentrations (CMC) and adsorption isotherms at the air-water surface. The corrosion inhibition efficiency was evaluated using electrochemical measurements under various conditions: different surfactant concentrations, hydrocarbon chain length, temperature, pH, and salinity. These electrochemical methods include linear polarization, electrochemical impedance spectroscopy (EIS), and Tafel slope method. Results are presented to show the inhibition effect dependence on the above mentioned factors. Mechanism behind corrosion inhibition was discussed.
Unipolar Resistive Switching and Associated Photo Response in Multifunctional BiFeO3 (BFO) Thin Films in Planar Geometry Grown By RF Sputtering
Authors: Katiyar Rajesh K , Misra Pankaj , Morell Gerardo , Katiyar Ram S.
Published: February 2020

We have studied the resistance switching phenomenon and associated photo response in BiFeO3 (BFO) thin films in planer electrode configuration. The films were grown by optimized RF sputtering process on SrRuO3 (SRO) buffered Pt/TiO2/SiO2/Si substrates. X-ray diffraction pattern and Raman spectrum of as grown film showed formation of high quality BFO thin films. To fabricate device structure top electrodes of platinum of thickness ~50nm and diameter ~200μm were grown on BFO layer using DC sputtering. The as grown film in planer geometry measurements showed high resistance of ~1MΩ and when voltage of ~ 4.0V was applied to the structure the resistance of the device switched to a low value of ~20Ω. It is noted that no forming process was required in this case. The repeatable switching of resistance of the Pt/BFO/SRO structure between low and high resistances has been observed with resistance ratio of ~ 105 and well defined switching voltages in the range of 1.75-2.5V and 3.0-4.0 V respectively in case of reset and set processes which is suitable for non volatile resistive random access memory applications. The precise control of the compliance current during the switching process from high to low resistance state revealed multiple resistances of low resistance state indicating possibility of multibit non volatile memory. To our knowledge, this type of resistance switching in BFO in planer geometry has been reported for the first time. The current conduction mechanism in the low resistance states was found to be dominated by the Ohmic behavior whereas in case of high resistance it followed poole frenkel emission at higher voltages. The efficient short circuit photo-current density was observed which was ~2 order in magnitude higher in case of low resistance state compared to high resistance state when illuminated with white light having power density of ~ 1kW/m2 . Further works are underway to understand the results and establish the associated photo voltaic effect and will be discussed at the meeting.
Simulation of the Ammonia Electrolysis Process
Authors: Diaz Luis A. , Estejab Ali , Botte Gerardine G.
Published: February 2020

Introduction

The electrochemical oxidation of ammonia, in alkaline media, has been proposed as an efficient alternative for the deammonification or wastewater. Furthermore, the ammonia electrolysis process has the potential to co-generate fuel grade hydrogen with just five percent of the energy required from water electrolysis, which makes this process attractive for its self-sustainable integration in wastewater treatment plants [1]. Motivated by the advantages of the ammonia electrolysis, Botte and members of the research team at the Center for Electrochemical Engineering Research (CEER) have performed extensive research in the ammonia electro-oxidation reaction. Through the analysis of well defined hydrodynamic electrochemical cells, coupled with mathematical modeling and parameters estimation, it was possible to establish a reaction mechanism and define the kinetic parameters that represent the intrinsic reaction kinetics of the ammonia electro-oxidation [2].

In this work, a simulation platform for an ammonia electrolysis flow cell is proposed to be implemented in ASPEN plus in order to achieve sensitivity and cost analysis along with process optimization. User defined platforms were developed using experimentally validated mathematical models of a parallel cell electrolyzer, which include the hydrodynamic behavior of the flow cell electrolyzer evaluated through experimental residence time distribution analysis.

References

[1] L.A. Diaz, G.G. Botte, Ind. Eng. Chem. Res. 51 (2012) 12167.

[2] L.A. Diaz, G.G. Botte, J. Catal. (Submitted for publication 2014).
Electrolyte Influence on Iron-Ion/Hydrogen-Ion Redox Flow Battery
Authors: Watson Venroy George , Kalu Egwu Eric
Published: February 2020

In the iron-ion/hydrogen redox flow cell, the redox flow battery electrolyte concentration has dramatic impact on the battery charging performance and OCV. Although chloride salt has greater charge carrying capacity per gram of salt in comparison to those of sulfates, optimal mixture of these electrolytes can yield a much higher battery performance than either electrolyte alone. The influence of electrolyte concentration on cell performance is investigated and the results will be presented. Charge polarization of the Fe2+ to Fe3+ was investigated using single and multiple electrolyte mixtures on both glassy carbon and platinum electrodes. Typical cyclic voltammograms obtained from FeCl2, FeSO4 and NH4FeSO4 and their mixtures are shown in Fig 1.
Composite Block Copolymer Electrolytes for Lithium Metal Batteries
Authors: Lee Yong-Gun , Yang Yooseong , Choi Hong Soo , Lee Je-Nam
Published: February 2020

Lithium metal has been widely investigated for next generation rechargeable batteries due to its extremely high theoretical specfic capacity. However, lithium dendrite formation at the lithium metal anode-electrolyte interfaces is considered to be one of major factors in deteriorating the performance of lithium metal batteries. To suppress the lithium dendrite growth, solid polymer electrolytes (SPE) with high mechanical strength and electrochemical stability have been studied to replace liquid electrolyte. In this case, using SPE in lithium metal batteries, low ionic conductivity and high interfacial resistance of SPEs are still remained critical problems. In order to achieve the high ionic conductivity and mechanical strength simultaneously in solid polymer electrolytes for lithium metal batteries, we applied block copolymer (BCP) composed of structural and ionic conducting domains in this study. In addition, we fabricated organic/inorganic hybrid block copolymer composite electrolytes with ionic liquids and nanoparticles for improving ionic conductivity and mechanical strength. The effects of composite block copolymer electrolytes were evaluated in terms of ionic conductivity as well as mechanical strength. In addition, interfacial resistance and ESW (electrochemical stability window) were also performed to understand the functions of hybrid components. In particular, these properties could be crucially affected by change of composition of block copolymer and hybrid components, which resulted in the different behavior inside polymer matrix and interface between electrode/electrolyte.
Spin-Lattice Coupling Studies of Electrode Material for 2nd Battery
Authors: Lee Seongsu , Kim Hyungsub , Kang Kisuk
Published: February 2020

Crystal and Magnetic structure of second battery electrode materials using neutron power diffraction is essential because of its sensitivity to observe the light element atom such as Li, Na and O. It is very important to define a position and occupation of conduction ion(Li-ion) for recognizing their reaction mechanisms. To do further advanced research combined Rietveld refinement and MEM (Maximum Entropy Method) is revealed the useful information for understanding the conduction mechanism.

By detailed structural analysis of electrode materials for rechargeable battery with neutron powder diffraction, we should understand an iso-structural change such as an oxygen ion tilting, a change of bond distance and an occupation variation etc. for studying the conduction mechanism. An iso-structural change in electrode is appeared by the charging/discharging, size-control, doping and spin ordering process. The control of iso-structure change as functions of several external conditions is very substantial to realize next generation 2nd battery with high-capacity, high-efficiency and good-safety. In this study, we have investigated the magnetic and crystal structure of electrode NaxFe3(PO4)2(P2O7) using neutron powder diffraction. We have observed that the spin ordering of Fe induces the iso-structure change of NaxFe3(PO4)2(P2O7). Even though the spin ordering of this material is happened at a very low temperature, the imagination about correlation between crystal and magnetic structure in electrode should be proposed us the clue to realize the new concept’ 2nd battery which the conduction property of electrode can be controlled by the spin ordering of magnetic ion.
Development of Nonaqueous Electrolyte for Multivalent Batteries
Authors: Liao Chen , Key Baris , Sa Niya , Burrell Anthony K. , Zhang Zhengcheng , Vaughey John T
Published: February 2020

The electrolytes play an important role in the multivalent batteries. Here we will report the development of a series of new electrolytes for magnesium batteries. The electrolyte has a high coulombic efficiency for Mg plating/dissolution and can be stable up to 2.8 V vs Mg. The preparation and characterization of the new electrolytes will be presented, including the syntheses, multinuclear NMR spectroscopy, the hypothesis of the product formation, the electrochemical characterization such as ionic conductivities and transport numbers. The capabilities of the electrolyte with Chevrel Phase Mo6S8 and other cathodes will also be discussed.
Enhanced Properties of Sulfur-Infiltrated Carbon Sphere with Conductive Polymer Coating for Lithium-Sulfur Batteries
Authors: Kim Do Kyung , Moon San , Jung Young Hwa , Kim Joo-Hyung
Published: February 2020

Lithium-sulfur (Li-S) battery is promising energy system with a high theoretical energy density (2500 Wh kg-1), which is ~7 times larger than those of the current LIBs (~387 Wh kg-1) utilizing the unparalleled theoretical capacity of sulfur (1675 mAh g-1). Sulfur as a cathode material also has other advantages such as non-toxicity, low cost, and abundance of raw materials.For all its virtues, several challenges such as an insulating nature of sulfur (conductivity ~10-30), a large volume expansion by up to 80 % upon full lithiation and a severe capacity fading during cycling still remained unsolved. Sulfur, unlike the insertion based electrode, suffers a serious of structural and morphological changes during cycling with the formation of high-order lithium polysulfides (Li2Sn, 2<n≤8) and low-order lithium polysulfides (Li2S2 and Li2S), which are insulators. Besides, the high-order lithium polysulfides are soluble in current liquid electrolyte at the early stage of discharging. The dissolution of high-order polysulfides results in the so-called shuttling effects.Those problems should be addressed for utilization of lithium-sulfur battery in consumer electronics.

In this present investigation, we developed sulfur infiltrated hollow carbon sphere with conductive polymer layer. The numerous small pores in carbon sphere were formed by evaporation of inner materials without damages of outer carbon layer. The conductive polymer layer (PEDOT) coated on the surface of carbon sphere could improve in the trapping of polysulfides and play a role in buffer layers against the volume changes of sulfur. The electrode design could improve the electrical performance with resolving the aforementioned issues.
Invited: Na-Ion Battery Technologies: Present Status and Update
Authors: Johnson Christopher S.
Published: February 2020

Na-ion batteries (sodium-ion batteries or SIB) that operate at ambient temperature present a great opportunity for the development of new energy storage systems that could be ideal for a myriad of applications. Low cost, long-term stability and great abundance of Na are the major drivers that can move this technology forward. Na batteries also could be positioned as a backup technology to Li-ion batteries, which would be of great value and insurance to the battery industry as one should not rely solely on one type of battery technology. Energy densities of SIB can vary greatly depending on the voltage and capacity of the active materials. While typically the energy densities of Na batteries are marginally lower compared to Li-ion batteries (about 30-50%), a host of new chemistry of compounds that are low cost with good performance are possible. For example, a cathode material that consists solely of Na Fe, and Mn would be low cost and highly safe. These elements are quite abundant and easily processed into active materials for the cathode using our new synthetic methods. In addition low-cost carbon materials such as those that are derived from pyrolysis of plant matter can serve as a reversible low-cost anode host for Na cations which are stored within graphene regions and nano-cavity or nanopores.

In this talk, I will discuss the desirable characteristics of SIB technology by providing examples on electrochemical and battery cycling performance results from new materials utilized as electrodes in SIBs.

Acknowledgement. This work was supported by the U.S. Department of Energy, U.S. DOE-BES, under ContractNo.DE-AC02-06CH11357.
First-Principles Study of the Thermodynamic Stability of Sodium Oxides As a Function of Temperature, Pressure and Particle Size; And Its Implications for Na−O2
Batteries
Authors: Kang ShinYoung , Mo Yifei , Ong Shyue Ping , Ceder Gerbrand
Published: February 2020

Recently, Na−O2 batteries have shown their potential as a high energy density electrical storage. Unlike Li−O2 batteries that have only one discharge product, Li2O2, the Na−O2 battery system has three potential discharge products: Na2O, Na2O2 and NaO2. Recent experiments observed either Na2O2 or NaO2 as a discharge product, and the performance of Na−O2 batteries is undoubtedly influenced by which particular discharge product is formed.[1-4] We investigated the thermodynamic stability of each phase as a function of temperature, O2 partial pressure, and particle size using first-principles calculations. Our results reveal that in bulk Na2O2 is the stable phase at the standard state (300 K, 1 atm) in agreement with experiments. Bulk NaO2 can only be formed at PO2 > 8.5 atm and/or T < 230 K (FIG. 1), both of which are unlikely to be accessed during the operation of typical Na−O2 batteries. To understand the relative stability of these two competing compounds at the nanoscale, we calculated their surface energies and found that the lowest surface energies of Na2O2 are in the range of 30−45 meV/Å2, while that of NaO2 is only 12 meV/Å2, rendering the possibility of stabilization of NaO2 over Na2O2 at the nanoscale. To confirm this idea, we constructed the phase diagram of Na2O2 and NaO2 as a function of particle size in FIG. 2. Indeed, the low surface energies of NaO2 stabilizes NaO2 nanoparticles, for example, up to 3 nm at PO2 = 0.1 atm. Moreover, we found that the nucleation energy barrier for NaO2 nanoparticles is much smaller than that of Na2O2, particularly when there is a small discharge overpotential and/or enough O2 supply. We expect our findings to direct efforts towards understanding and controlling the formation of desired Na−O compounds in battery operation, and furthermore invigorate interest on the potential of Na−O2 batteries.[5]

References

[1] P. Hartmann, C. L. Bender, M. Vracar, A. K. Durr, A. Garsuch, J. Janek, and P. Adelhelm, Nat Mater 12, 228 (2013).

[2] Q. Sun, Y. Yang, and Z.-W. Fu, Electrochemistry Communications 16, 22 (2012).

[3] S. K. Das, S. Xu, and L. A. Archer, Electrochemistry Communications 27, 59 (2013).

[4] J. Kim, H.-D. Lim, H. Gwon, and K. Kang, Physical Chemistry Chemical Physics 15, 3623 (2013).

[5] S. Kang, Y. Mo, S. P. Ong, and G. Ceder, Nano Letters 14, 1016 (2014).
Fully Fluorine-Free Liquid Electrolytes for Na-Ion Applications
Authors: Michalczewski Krystian , Bitner-Michalska Anna , Gajewska Agnieszka , Poterala Marcin , Dranka Maciej , Zukowska Grazyna Zofia , Kalita Michal Jan , Marcinek Marek
Published: February 2020

Sodium-based batteries are interesting candidates, when replacement of the lithium- and lead-based batteries ins taken into consideration. The advantages over lead-based systems is based mainly on the low weight and low impact on the environment of the sodium in comparison to lead. Therefore, use of the sodium-based batteries is interesting when high power density is needed. The main advantage of sodium in comparison to lithium is based on the fact that sodium is both the most abundant alkali metal on Earth. It is worth to remember that application of the Li-ion technology in stationary batteries applications and in the electric vehicles industry is limited due to insufficient sources of lithium. Such problems in case of sodium-based batteries do not occur. Moreover, sodium salts are much cheaper than respective lithium salts.

Up to now, several sodium-based batteries were constructed. First sodium-sulfur battery, unfortunately, exhibiting low energy density, was built in 1960s. This technology was developed and NASICON electrolyte was introduced to it in 2000s. This battery was of superior energy density. On the other hand, both electrodes need to be liquid in such system. Therefore, the operating temperature of such battery have to be higher than 150°C, and the electrode materials in it need to be melted before it starts. This make impossible use of such batteries in applications in which fast start is desired. The same disadvantage has Na-NiCl2 battery, which also exhibit low energy density.

It is believed that the problems of the high operating temperatures for sodium-based systems can be solved by designing of sodium-ion power sources, per analogiam to the lithium-ion battery technology. The main problem related to this system is to design and obtain the electrolyte which is stable against electrode materials. Naturally, the problems of the Na-ion are similar to this of lithium-ion, however, several novel issues occur. The affinity of the sodium to the fluoride is higher than to lithium, therefore, the decomposition of the salt is more intensive. There are also differences when the affinity of lithium and sodium to the solvent molecules is discussed. Due to this, the simple substitution of the lithium salts with the sodium ones can give not fully sufficient results. Therefore, new electrolytes, containing novel salts and solvents other than carbonates, need to be tested in such systems.

In the presentation, the ion transport properties of the systems containing novel sodium salts with heteroaromatic anion will be presented. The electrochemical properties of the electrolytes will be confronted with the coordinating properties of both cation and anion in the solution and in the solid-state. Also interactions in the salt solvates will be discussed.
Reformer-Integrated Thin-Film Solid Oxide Fuel Cell for Ethanol Fuel
Authors: Kang Sungmin , Chang Ikwhang , Cha Suk Won
Published: February 2020

Ethanol reformer and thin-film solid oxide fuel cell are integrated on single nano-porous anodic aluminum oxide(AAO) substrate. Manganese doped cobalt catalyst is utilized as fuel reformer which is deposited on one side of the substrate, and thin-film single cell is fabricated on another side of the AAO, which is made of Pt, Ru and YSZ thin films. Electrochemical performance is tested at 500℃, in the electrical heater, supplied by fuel-water bubbled inert gas stream. Fuel-water saturated inert gas flows into the reformer, and becomes hydrogen gas, COx, methane, etc. Reformed gas diffuses from reformer to single cell anode, passing through the nano-pores of AAO substrate. Although many carbon-containing substances such as COx or methane are chemically formed, the anode of single cell operates for considerably long time while maintaining high performance, because ruthenium in anode layer protects the catalyst particles from poisoning. This reformer-integrated cell structure acts as a direct-hydrocarbon fuel cell.
Effect of Atmospheric Carbon Dioxide and Strontium Content on Surface Segregation in Strontium Doped Lanthanum Cobalt Iron Oxide Thin Films
Authors: Yu Yang , Cetin Deniz , Luo Heng , Ludwig Karl F , Pal Uday Bhanu , Gopalan Srikanth , Lin Xi , Basu Soumendra Nath
Published: February 2020

This study investigates surface segregation behavior and phase formation in LaxSr1-xCo0.2Fe0.8O3-δ (LSCF), a commonly used cathode material for solid oxide fuel cells (SOFCs). (100)-oriented LSCF thin films with varying ‘x’ values were deposited on (110)-oriented NdGaO3 (NGO) substrates by pulsed laser deposition (PLD). Compositional changes on the surface of LSCF thin films were measured using total reflection x-ray fluorescence (TXRF) technique in real time at 800°C under different CO2 partial pressures. Ex-situ electronic structure measurements were carried on the post-annealed samples using hard x-ray photoelectron spectroscopy (HAXPES). The thin-films were also characterized in cross-section by high-resolution transmission electron microscopy (HRTEM), and composition profiles in the LSCF matrix adjacent to the surface segregated phases were analyzed using energy-dispersed x-ray spectroscopy (EDS). The thermodynamics and kinetics of the segregation and phase formation phenomena as a function of atmospheric CO2 partial pressure and Sr content is discussed in this presentation.
NiO/YSZ Reduction for SOFC/SOEC Studied In Situ by Environmental Transmission Electron Microscopy
Authors: Simonsen Søren Bredmose , Agersted Karsten , Hansen Karin Vels , Jacobsen Torben , Wagner Jakob Birkedal , Hansen Thomas Willum , Kuhn Luise Theil
Published: February 2020

SOFCs/SOECs are typically composed of ceramic materials, which are highly complex at the nano-scale. Scanning and transmission electron microscopy (SEM and TEM) are routinely applied for studying these nano-scaled structures post mortem, but only few SOFC/SOEC studies have applied environmental TEM (ETEM). ETEM offer the possibility to record image series (movies) of the ceramic nanostructures with atomic scale resolution during exposure to a reactive gas environment at elevated temperatures. The present contribution focuses on the typical reduction preparation step for the state-of-the-art Ni/YSZ (YSZ = Y2O3-stabilized ZrO2) based anodes for SOFC and cathodes for SOEC. Specifically, the reduction of nickel oxide to form the catalytically active nickel surface is monitored directly at the nano- and atomic scale by using an ETEM. The reduction process was followed while exposing NiO/YSZ and pure NiO to H2 at temperatures from room temperature to ca. 800°C. The NiO/YSZ was prepared by crushing down a tape casted and sintered model anode/cathode into a fine powder. Previous studies based on averaging techniques have shown that the reduction of pure NiO is a relatively rapid process, while the reduction of NiO/YSZ is slower, which indicates that the presence of YSZ inhibits the reduction of NiO. In the presents in situ experiments the temperature dependent reduction profile are found similar for the both nano-scaled NiO and NiO/YSZ sample. The apparent inhibitive effect of YSZ on NiO reduction is therefore not caused by a direct interaction between NiO and YSZ, but is an indirect effect depending on the NiO being integrated in a macroscopic network of NiO/YSZ. A Titan E-Cell 80-300ST TEM was used for the in situ work in combination with the chip-based heating holder from Protochips which facilitated rapid temperature ramping for example from room temperature to 800°C in only 1 s. The ETEM results are compared to complementary averaging techniques such as thermo-gravimetric analysis (TGA) and X-ray diffraction analysis (XRD).

The figure presents a TEM image series of NiO during exposure to 2 mbar H2 and constant temperature ramping rate of 1°C/min. The NiO observed in the first image at 320°C is dense. From the lower left corner a front of porous Ni is progressing until full reduction at 340°C.
Thermally Robust Thin-Film SOFCs for Mobile Application
Authors: Kim Kun Joong , Park Byung Hyun , Choi Gyeong Man
Published: February 2020

Metal-supported solid oxide fuel cell (MS-SOFC) is promising for use at intermediate temperature range (500-700°C) since metal could provide the good thermal conductivity and the mechanical strength in addition to the low cost. The MS-SOFCs are often fabricated by co-firing in reducing atmosphere to avoid metal oxidation. However, the inter-diffusion between Fe/Cr in stainless steel (STS) and Ni in the conventional cermet anode is detrimental to the electrochemical performance of the cell. In this study, a multi-layered cell consisting of a yttria-stabilized zirconia (YSZ) electrolyte, and a porous anode layer, and a ferritic STS support, was fabricated using tape casting and co-firing process.

The cell with alternative anode was compared with that with conventional anode in terms of microstructure, Cr poisoning, and thus anodic performance. It was found that the use of diffusion barrier layer (DBL) reduces the reaction between conventional Ni-cermet anode and STS and provides a stable performance. The performance can be further enhanced with an alternative anode.
3D Multiphysics Modelling and Design Optimisation of a Complete SOFC System Operating in Jülich
Authors: Peksen Murat , Al-Masri A , Peters Ro. , Blum L , Stolten D
Published: February 2020

Forschungszentrum Jülich has been giving particular attention to the high-end 3D multiphysics modelling of complete fuel cell systems, including all auxiliary components such as fuel cell stack, afterburner, heat exchanger, pre-reformer and baffle plates. Our previous full 3D system model has been developed so that the current emphasis of research has been given to the 3D design optimisation of the fuel cell system in terms of thermomechanical behaviour and long-term stability. The long-term steady state operation has been the focus. Coupled CFD/FEM is used to predict the thermofluid flow and heat radiation, electrochemical and chemically reacting species transport, as well as the thermomechanics, including the long-term creep behaviour and elastoplasticity. The
Invited: Corrugated Cell Structures in Membrane Electrode Assemblies
Authors: Grot Stephen
Published: February 2020

The traditional Proton Exchange membrane fuel cell stack with its bipolar plates with grooved flow channels,

flat membrane electrode assemblies (MEAs), seals and end-plates has been the dominant

method of construction of multi kW fuel cells for the past 40 years. Smaller sub-watt and

portable applications have explored novel cell design variations such as “jelly roll”

concepts but none have been able to achieve the power density of the traditional

stacked plate design. The primary reason for this is the efficient collection of the current

and the compact packing of the MEAs.

However at the present time one of the most challenging aspects of traditional PEM fuel

cell stacks is the difficulty to achieve the platinum catalyst utilization target of 0.2 g

Pt/kWe set forth by DOE. Good catalyst utilization can be achieved with state-of-theart

catalyst coated membranes (CCM) when ultra-low catalyst loadings (< 0.1 mg/cm2)

are used at lower current. Unfortunately when ultra-low loadings are used, the peak

power density is lower as compared to conventional loadings. Thus a larger total

active area and a larger bipolar plate is needed which results in a lower overall stack

power density and as such the DOE targets of power density can not be achieved

simultaneously

We thus now introduce in this proposal, our novel concept to increase the available MEA

active area by 2x or more while maintaining the same bipolar plate size. This is

achieved via a corrugated MEA sandwiched between bipolar plates. This is much like

corrugated cardboard, where the center corrugation (or flute) is the MEA. The

corrugations then form the gas channels thus there is no need for forming flow field

channels in the bipolar plates. Thus the gas diffusion media as well as the membrane needs to be formed in the corrugated structure. We will describe the state of our development on this approach.
Invited: Micro Fuel Cells: Can We Apply Them to a Successful Market?
Authors: Esquivel Juan Pablo , Del Campo Francisco Javier , Gomez de la Fuente Jose Luis , Rojas Sergio , Sabate Neus
Published: February 2020

Fuel cells convert chemical energy into electrical energy. Their high energy density together with the possibility to operate at room temperature using liquid fuels identified them as potentially suitable for portable applications more than a decade ago. Despite their promising capabilities, they have failed to oust lithium batteries from the consumer electronics market: batteries have successfully evolved into tiny packages that are very easy to use, rechargeable and that can meet the power demands of current portable appliances. In contrast, fuel cells have to be fed with a liquid fuel and require an ion-conducting membrane that prevents mixing of oxidant and reducing species, which has to be permanently hydrated to ensure optimal performance. The complexity associated to the use of this membrane was overcome some years ago with the development of the so-called microfluidic fuel cells, in which the separation of reactants is achieved by forcing them to flow in parallel in a microfluidic channel at low Reynolds numbers. Microfluidic fuel cells yield significant amounts of energy with a very simple architecture. In her presentation, Dr. Sabaté will talk about what are the challenges and opportunities for micro fuel cells to find a market niche where they can take advantage over other miniaturised power sources.