bluuebunny/crossref_metadata_2025 huggingface dataset:
100k Cycles and Beyond: Extraordinary Stability for Au@MnO2 core@Shell nanowires Imparted By Gel Electrolyte
Authors: Le Thai Mya , Penner R. M. , Thesma Chandran Girija
Published: February 2020

Nanowire electrodes for batteries and super-capacitors can produce superior power relative to films of the same materials.  But the Achilles Heel of nanowires is their susceptibility to degradation and failure.  This is particularly true for materials that employ Faradaic reactions requiring ion insertion/deinsertion for energy storage.  Here we describe the preparation of arrays of ultra-long (2.5 mm) Gold@δ-MnO2, core@shell nanowires.  Gold@δ-MnO2 nanowires are prepared on glass surfaces using a variant of the Lithographically Patterned Nanowire Electrodeposition process.  All nanowire capacitors prpared from these ultra-long nanowires produce state-of-the-art metrics for energy and power in MnO2-based systems, but they demonstrate irreversible capacity loss exceeding 20% in ≈4000 - 8000 cycles.  This cycle stability nevertheless represents the state-of-the-art for MnO2 based electrodes.  Now we have discovered that the addition of poly(methylmethacrylate)(PMMA) to the propylene carbonate (PC) electrolyte extends cycle stability to 100,000 cycles and beyond.  Other energy storage metrics of these systems are not degraded by the PMMA.  In this talk, I describe the results of our experiments, and present data on the charactrerization of these Gold@δ-MnO2 nanowire systems in PC electrolyte and PC electrolyte containing PMMA, before and after cycling.
Electrochemical Fabrication of 3D Gradient Refractive Index Micro-Optics
Authors: Braun Paul V
Published: February 2020

Via electrochemical etching of silicon, followed by materials conversion, 3D gradient refractive index micro-optics were formed.  Elements including flat lenses, Bragg mirrors, polarization sensitive optical splitters and structures with nearly arbitrary refractive index distributions were formed with a particular focus on micro-optics important for solar energy harvesting.  The conversion from silicon to silica and titania enabled the optics to operate in the visible with minimal loss, something particularly important for solar energy harvesting applications.
Electrochemical Upgrading of Bio-Oil
Authors: Diaz Luis A. , Lister Tedd E. , Padmaperuma Asanga , Lilga Michael , Job Heather , Lemmon Teresa , Tran Quan
Published: February 2020

Alternative fuels derived from biomass “biofuels” are an attractive alternative to substitute limited and non-renewable sources of energy. Bio-oil generated from the pyrolysis of biomass is a complex micro-emulsion with high levels of oxygen and acids, which lead to increases in viscosity, phase separation, and degradation as it ages. This instability of bio-oil complicates storage, transportation and downstream processing. Currently, catalytic upgrading of is performed to stabilize the bio-oil by means of the reduction of the oxygen content. However, the current hydrothermal upgrading technologies operate at high hydrogen pressures, up to 2000 psi, and temperatures that lead to coke formation in the catalyst bed. A milder method is needed to convert unstable carbonyl species to more stable alcohols as an intermediate step before hydrothermal treatment.

In this work an electrochemical approach has been investigated for the upgrading of bio-oil at low temperature using a proton exchange membrane (PEM) electrolyzer. The PEM electrolyzer was selected for performing the conversion as it avoids the need to add electrolyte to the oil which would cause phase separation and require later removal. Work has primarily focused on using cation-exchange membranes where protons are generated in the anode and travel through the membrane to the cathode surface. The hydrogenation of the bio-oil at the cathode competes with hydrogen evolution. Work has focused on using various electrode cell architectures and electro-catalysts to reduce both model compounds and actual pyrolysis oil derived from wood. 

While further work is needed, promising results have been observed with reduction of carbonyl groups and phenolic rings. A description of the work conducted and discussion of the results will be presented.
The Role of Renewable Hydrogen in Sustainable Manufacturing
Authors: Ayers Katherine E
Published: February 2020

Reduction of carbon dioxide emissions and other pollutants is a critical need worldwide for sustainability.  Transportation is one major contributor of greenhouse gas emissions, and there is significant debate over the relative merits of fuel cells vs. batteries as the energy system.  Batteries provide improved energy efficiency, but do not provide the driver with the same experience in range and fueling time as the fuel cell option.  However, a major drawback for fuel cells is the lack of hydrogen fueling infrastructure.  While even hydrogen from natural gas provides a well to wheels emissions benefit, hydrogen from non-carbon based sources has had challenges in being viewed as a cost effective option, largely because the electricity cost dominates the analysis.

While much attention has been directed towards hydrogen as a transportation fuel, it should also be remembered in developing global solutions that hydrogen is also a major world chemical feedstock.  Most of the world's hydrogen goes to hydrogenation of fats and oils, and ammonia generation.  Production of ammonia is one of the world's largest consumers of energy, largely based on the energy consumed in the generation of hydrogen from natural gas.  The Haber Bosch process occurs at high pressure (150–300 atm) and high temperature (400°–500°C), and accounts for about 1-2% of the world's annual energy consumption (5% of the world's natural gas). In addition, the fossil fuel reforming of natural gas to hydrogen results in substantial carbon dioxide (CO2) emissions. 

Hydrogen production from water electrolysis requires more energy per kilogram of hydrogen than natural gas reforming (when only considering the generation step), but has the option of using renewable energy as the primary energy source.  In addition, polymer membrane-based electrolysis is very well suited for load-following applications.  These devices can therefore operate primarily on excess electricity from what would otherwise be stranded renewable resources.  Finally, because an electrolyzer is a flow cell, like a flow battery, the reactants and products are stored separately from the electrochemical device, which is more attractive for very long charge times.  Higher capacity can be added simply by adding storage tanks.  This talk will discuss the current status of electrolysis and challenges in bridging the gaps between present commercial status and future optimized solutions in this context.

In addition, an analysis of energy of manufacturing for electrolyzers themselves shows opportunities for improvement.  One energy intensive process is the manufacture of the membrane electrode assembly.  The energy required to deposit and bond the catalyst to the membrane can be reduced through advanced manufacturing processes, and use of less catalyst reduces the original refining energy, which is also a significant contribution.  Progress in reduction of manufacturing energy will also be briefly discussed.

Figure 1
Nafion: A Thermodynamic Sketch
Authors: Leddy Johna , Rathuwadu Nadeesha
Published: February 2020

Nafion®, the most commonly employed ion exchange polymer, serves as both a separator and a sensor platform. After more than 30 years of use, properties of Nafion have been measured and various models of Nafion have been proposed.

Many properties of Nafion have been measured as a function of water content and hydration [1]. This includes selectivity of alkali metal cations over protons, glass transition temperatures, decomposition temperatures, mobilities, transport numbers, conductivity, solvent swelling, gas solubilities, mechanical properties, and density.

Here, a simple thermodynamic sketch of Nafion is presented that characterizes its varied properties.

Density specifies water content that varies with the intercalated cations in both Nafion membranes and recast Nafion films [2,3]. Nafion is a known biphasic material composed of interconnected solvent filled domains and fluorocarbon domains. Because the dielectric constant reflects the ability of a matrix to support ionization, ions are found in the solvent filled domains. From the density and equivalent weight of Nafion, ion concentrations in the solvated domains are found.

Electrochemical potential μj
α for the ions is calculated based on the ionic strength in the solvated domains.

μj
α = μj
α,0 + RT ln aj
α + zjFφ = μj
α,0 + RT ln Υj
αcj
α + zjFφ

Because common models such as Debye Hückel, extended Debye Hückel, and Davies are restricted to ionic strengths well below those found in the solvated domains of Nafion, later models such as those of Stokes and Robinson are used to derive an expression for the activity coefficient.

The activity coefficient equation is used to fit literature data for selectivity, solubilities, swelling, and thermal, transport, and mechanical properties. Self consistent values for waters of hydration (and solvent molecules of solvation) are found for monocations across the literature on numerous measured properties reported as a function of solvent content.

This thermodynamic sketch of Nafion allows calculation of Nafion properties based on activity coefficients and electrochemical potential. The model also provides a practical means for design of Nafion materials with selected properties.

References

[1] J. Leddy, Modification of Nafion Membranes: Tailoring Properties for Function, ACS Symposium Series, Nanomaterials for Energy, edited by J. Liu, S. Bashir, and L.-D. Chen (2015).

[2] K.J. Oberbroekling, D.C. Dunwoody, S.D. Minteer, J. Leddy, Anal. Chem. 2002, 74, 4794-4799.

[3] L.A. Zook, J. Leddy, Anal. Chem. 1996, 68, 3793-3796.
A Quantum Dynamics View of Electric Double Layer in PEFC
Authors: Zhou Xiangyang
Published: February 2020

We conducted atomistic simulation of the interfaces between Nafion electrolyte and electrode in polymer electrolyte fuel cells (PEFCs). We have accomplished: 1) simulation of the atomic structure of the sulfuric acid/Pt, sulfuric acid/carbon, Nafion/Pt, and Nafion/carbon interfaces; 2) evaluation of the ionic potential distribution at the interfaces; 3) evaluation of the electronic potential distribution at the interfaces; 4) simulation of the dynamic trajectories at the interfaces; and 5) evaluation of the exchange current density at the interface. The following findings have been obtained. Firstly, at the interfaces, on the top of the electrode surface, water molecules and other small molecules arrayed into three highly ordered layers. The ordering or symmetry of the layers is similar to that of the electrode surface. Secondly, the potential difference or electric field is completely different for ions and electrons. Generally, the ionic potential reveals a large step at the interface. Adsorption of hydrogen and oxygen increases the height of the step. On the contrary, the electronic potential is continuous across the interface for the middle potential range but discrete for very high and low potential levels (Fig. 1). It seems that the existing definition of so-called electrochemical potential or potential difference across the electric double layer (EDL) is not valid. In fact, according to the simulation results, there are two “interface potentials”, ionic potential and electronic potential. Thirdly, the simulation proves that adsorbed hydrogen and oxygen do increase the exchange current density at the interface. The implications of the findings to the theory of electrochemical electron transfer kinetics, including the conditions for electron transfer at the interface and the popular Butler-Volmer equation are discussed.

Figure 1
Simulation of Surface pH-Effects and Near-Surface Ion Distributions during Reactions at the Solid/Liquid Interface
Authors: Auinger Michael
Published: February 2020

Many processes such as the corrosion of metals, the charging of a battery or reactions in electrocatalysis are prone to local activity changes of reactive species. In such complex systems, these changes often define the macroscopic behavior. However, a clear experimental deduction of individual reactions on the overall current signal appears to be very difficult in many cases. Whereas the influence of the local ion activities near the surface, exemplified for the Hydrogen Oxidation Reaction (HOR) / Hydrogen Evolution Reaction (HER) on Pt in H2-saturated solutions has been discussed previously [1], it could be shown that for fast reactions, thermodynamic modeling predictions agree well with measured cyclic voltammograms [1, 2]. Further it was demonstrated that even in a weakly buffered solution (up to 10 mM total buffer concentration), the analytical equation not only reflects the experimental current-voltage characteristics but is also capable to deliver the local distribution of all contributing ions in the diffusion zone.

This work critically reviews the original modeling approach [1], illustrates its limitations and presents recent developments towards a more general model by including the local enrichment of buffer species and (slow) reaction kinetics, depending on the actual conditions at the electrode surface and in the bulk solution. Obtained results will be compared to recent progress in the field [3, 4], showing that the influence of local activity changes near the surface are likely to affect the behavior of the macroscopic system. This becomes particularly relevant for local electrochemical processes such as either atmospheric corrosion, the dissolution of a cathodic protection layer (e.g. Zn coated steel) or other reactions that consume/produce a large amount of protons.

While the modeling approach presented in this work cannot be directly used to derive the properties of a complex electrochemical system with a large multitude of reactive species and reaction steps, it remains helpful to deduce the influence of individual components on the macroscopic system.

References

[1]           M. Auinger, I. Katsounaros, J. C. Meier, S. O. Klemm, P. U. Biedermann,  A. A. Topalov, M. Rohwerder, K. J. J. Mayrhofer, Phys. Chem. Chem. Phys. 13 (2011) 16384-16394.

[2]           I. Katsounaros, J. C. Meier, S. O. Klemm, A. A. Topalov, P. U. Biedermann, M. Auinger, K. J. J. Mayrhofer, Electrochem. Commun. 13 (2011) 634.

[3]           D. Strmcnik, M. Uchimura, C. Wang, R. Subbaraman, N. Danilovic, V. van der Vliet, A. P. Paulikas, V. R. Stamenkovic, N. M. Markovic, Nat. Chem. 5 (2013) 300.

 [4]          M. D. Arce, H. L. Bonazza, J. L. Fernandez, Electrochim. Acta 107 (2013) 248.
Importance of Excitonic Effect in Charge Separation at Quantum-Dot/Organic in-Terface: First-Principles Many-Body Calculations
Authors: Lee Donghwa
Published: February 2020

Charge separation of excitons in materials is one of the most important physical processes to utilize the solar energy in diverse devices including solar cells and photo-catalysts. Heterogeneous interfaces with the so-called type-II character are often employed to infer the interfacial charge transfer in this context. As a simple criterion for designing such an interface, the energy alignment of the quasi-particle states together with the exciton binding energy of electron-donating materials is often discussed in the literature. However, an accurate description of the effect of exciton binding at the interface has not been investigated extensively. Although density functional theory (DFT) is a powerful method to investigate various elec-tronic properties of materials, incomplete description of many-body interactions often leads to an incorrect interpretation of the energy level alignment. While Many-Body Perturbation Theory and Quantum Monte Carlo (QMC) are promising in this context, much more work is necessary to assess how well these methods perform in practice. In this talk, I will discuss how significant the excitonic effect can affect charge separation process at heterogeneous interfaces between PbS quantum dot and thiophene oligomers by employing QMC calculations. Our study shows that charge transfer excitons can act as a trap states for electron-hole recombination instead of facilitating charge separation. This work has been published in Nano Letters.
(Invited) Numerical Simulations of Mass Transport Using Separation of Variables: an Old Method Rejuvenated with Symbolic Algebra Software
Authors: Holm Thomas , Sunde Svein , Seland Frode , Harrington David A.
Published: February 2020

Separation of variables is a classic method of solving partial differential equations, such as the convective diffusion equations that are ubiquitous in electrochemistry. It leads to infinite series solutions, which are exact analytical solutions. However, various parameters involved in the series have to be numerically evaluated, and the series converge rather slowly, which has meant that this method has not been used for practical numerical calculations of concentration profiles for electrochemical problems. We show here that these difficulties can be overcome, and demonstrate the use of the symbolic algebra program Maple in a practical implementation of this for steady-state convective diffusion past electrodes in a 2-D channel [1].

The key to successful implementation has been the use of asymptotic formulas to reliably locate the eigenvalues, so that the numerical solver does not miss any.

The method has the following advantages:

1. It is a mesh-free method, so a separate step of validating the mesh or grid is not necessary.

2. The global error can be estimated by evaluating the series to more terms.

3. Each segment (above an electrode or insulating section) is solved at once, so changing the length of an electrode does not change the difficulty of the calculation.

4. Workup of the concentrations to derived quantities such as currents or collection efficiencies can be done without any degradation of accuracy. 

The present implementation assumes diffusivities of reactant and product are equal, which allows the generation of both concentration profiles in a single calculation by using a recently developed transformation method [2]. It also neglects axial diffusion. Future work will seek to remove these limitations, and extend the results to 3-D and time-dependent systems.

References: 

[1] T. Holm, S. Sunde, F. Seland and D.A. Harrington, A Semianalytical Method for Simulating Mass Transport at Channel Electrodes, J. Electroanal. Chem.,745 (2015) 72-79.

[2] D.A. Harrington, Rules to Transform Concentrations and Currents for Irreversible Reactions to those of Quasireversible Reactions, Electrochim. Acta., 152 (2015) 308-314.

Figure 1. Concentration Profile for a Collection Efficiency Calculation at Electrodes in a Channel. X = distance along channel, Y = distance across channel (dimensionless variables). Electrode between X = 0 and X = 1 producing species at the limiting current, Electrode between X = 2 and X = 3 consuming species at the limiting current.

Figure 1
(Invited) Nanoelectrochemical Modeling: Elucidation of the Reaction Mechanism
Authors: Mirkin Michael V. , Yu Yun , Zhou Min , Oleinick Alexander , Svir Irina , Amatore Christian Andre
Published: February 2020

We recently introduced new methodology for detecting charged reactive intermediates of heterogeneous processes and used it to investigate the oxygen reduction reaction at polycrystalline Pt.  A nanometer-sized pipette filled with organic solvent immiscible with the external aqueous solution was used as a tip in the scanning electrochemical microscope (SECM) to detect and identify a short-lived superoxide intermediate and determine the rate of its generation at the catalytic Pt substrate.  The interpretation of that experimental data was based on a simplified model that left a number of open questions about superoxide desorption and its lifetime in neutral aqueous solution.  Here we report the results of finite element simulations based on a more exact model and aimed at the detailed mechanistic analysis of this system.
First Principles Investigation of Photocatalytic Conversion Process at TiO2 Surfaces
Authors: Lee Donghwa
Published: February 2020

Photo-catalytic conversion of CO2 into hydrocarbon fuels is an ideal avenue for mitigating the CO2 emission. Ever since the photo-catalytic reduction of CO2 was discovered to take place at TiO2 surface a few decades ago, many have been extensively working to improve the photo-catalytic reaction on the TiO2 surface. It is commonly believed that the photo-catalytic reduction of CO2 into methanes/methanols could take two different reaction routes through an intermediate step forming formic acid or carbon mono-oxide. Using first principles calculations, we investigated that both reaction mechanisms on the surfaces of bulk Anatase TiO2(101) and a small TiO2 nano-cluster. We will discuss significant differences of conversion process that we have observed for these two cases and elucidate role of different physical quantity.
(Invited) Advanced Control of Two-Phase Flow in Gdl for PEM Fuel Cells
Authors: Wang Yun
Published: February 2020

Water management is a central issue in the development of polymer electrolyte fuel cells (PEFCs): liquid water could considerably increase the oxygen transport resistance and hence the transport polarization whereas dryness dehydrates the electrolyte membrane, raising the Ohmic voltage loss. PEFCs produce water during operation and the electro osmosis enlarges the water imbalance between the anode and cathode sides, making water management a complex operation that requires a careful treatment. Issues such as diffusion media dewetting, anode rehydration, and internal humidification have received much attention in recent years. Modeling, numerical simulation, and advanced imaging techniques are capable of revealing details of transport phenomena, and are a powerful tool for elucidating water management.

In this talk, I will cover the below subjects which are the major contributions of UC Irvine to water management: 1.) nonisothermal two-phase flow modeling; 2.) transient dewetting of gas diffusion layer (GDL); 3.) theoretical approach of defining control parameters to characterize two-phase flows; and 4.) experimental evaluation of two-phase flow in PEFCs using neutron radiography. In 1.), a nonisothermal two-phase model, accounting for vapor-phase diffusion and heat pipe effect, was developed and implemented to investigate liquid water distribution. The model was validated in detail against liquid water distribution across GDLs. In 2.), a transient model was developed to capture the phase change and interface movement in PEFCs. A case study will be presented to show the timescale of material dewetting at different regions of GDLs. In 3.), A dimensionless parameter Da0 will defined to characterize the in-plane two-phase region. When Da0 is over 1, part of the GDL region is free of water due to waste heat production and evaporation. A liquid-free GDL region is defined and related to Da0. Impacts of operating temperatures, GDL thermal conductivities, and current densities on the region will be discussed. In 4.), I will present an in-situ study to examine the water content in PEFCs using neutron radiography. Various conditions such as different PTFE loadings in the GDL including the micro-porous layer (MPL), different flow fields (single-channel and quad-serpentine channels), and co-/counter-flow configurations are investigated.
Cell Reversal Phenomenon during Start-up of Alkaline Fuel Cell Stacks
Authors: Akhtar Naveed
Published: February 2020

Successful start-up of any fuel cell is one of the basic and mandatory requirements before a useful power can be drawn out of it. In a liquid electrolyte alkaline fuel cell, the start-up dynamics are slightly more complicated as compared to the solid electrolyte type of fuel cells.  The reason being that besides reactant gases, liquid electrolyte has to be present. This is to ensure that it acts as a barrier between the reactant gases to allow a useful cell potential to be obtained. During start-up, the competition between each of the fluid’s dynamics dictates the voltage of the cell. The cases, in which the cells are either facing a lag in air supply or a lag in fuel supply, would be temporarily starved of reactants and will not be able to establish a useful open circuit potential. The experiments show that during such events, the underlying cells may reverse in polarity and locally damage the electrodes. This damage can be prevented if the local reactant supply is restored as early as possible; therefore, the cells are able to generate useful driving potentials. The analysis suggests that the presence of air/fuel mixture in a single compartment is the likely reason for cell reversal.
Theoretical Calculations of Ammonia Oxidation Kinetics on Platinum, Iridium and Their Bimetallic Clusters
Authors: Estejab Ali , Botte Gerardine G
Published: February 2020

Introduction

Population increase and technology growth are the main reasons for increasing demand of energy sources and fossil fuels consumption as the main energy source consequently increases. However, these fuels emit large amounts of greenhouse gases to the atmosphere. Moreover, they are not renewable resources. Hydrogen as an energy carrier is attractive because the only product of its combustion is water. However, production and storage of hydrogen raises concerns about costs and safety. Ammonia (NH3) can be used as a hydrogen source and it requires about 5% of the thermodynamic cell voltage (0.06 V) needed to produce hydrogen from water [1-4].

2NH3(aq)+6OH- → N2(g)+6H2O+6e-    E°=-0.77V vs. SHE  (1)

6H2O+6e- → 3H2(g)+6OH-    E°=-0.83V vs. SHE  (2)

2NH3(aq) → N2(g)+3H2(g)    E°=0.06V (3)

Objectives

In order to decrease the cost of hydrogen production through ammonia electrolysis, the kinetics of the process should be known. While experimental techniques are the primary procedure for elucidating the kinetics especially on monometallic surfaces, theoretical calculation can be fascinating in terms of investigation of intermediates produced during the surface reaction. These intermediates can not be recognized with traditional experimental methods on monometallic, bimetallic or polymetallic surfaces. In this work, density functional theory calculations are performed on four platinum-iridium clusters, Pt3-xIrx (x=0-3) to examine ammonia oxidation in alkaline media. The adsorption of NH3-x(x=0-3) on these clusters and the effect of cluster composition on the adsorption are investigated. The hybrid B3LYP level of theory is used in Gaussian 09 along with the LANL2DZ and 6-311++g basis sets.

Results

Our Preliminary results for the HOMO-LUMO gap of adsorbed species on clusters, combined with activation and dissociation energy calculations of sequential dehydrogenation reactions of NH3→NH2→NH→N showed that Ir3 is more active than Pt3for ammonia oxidation. Additionally, the combination of iridium and platinum makes a more favorable pathway for the ammonia oxidation reaction. However, experimental analyses indicate improved reactivity on platinum in comparison to iridium in ammonia oxidation. This suggests the possibility of two different mechanisms for ammonia oxidation on platinum and iridium. 

References

[1]        F. Vitse, M. Cooper, and G. G. Botte, "On the use of ammonia electrolysis for hydrogen production," Journal of Power Sources, vol. 142, pp. 18-26, 2005.

[2]        G. G. Botte, "Electrochemical method for providing hydrogen using ammonia and ethanol," U.S. Patent No. 8,221,610 2012.

[3]        G. G. Botte, M. Cooper, and F. Vitse, "Electro-catalysts for the oxidation of ammonia in alkaline media," U.S. Patent No. 7,485,211 2009.

[4]        B. K. Boggs and G. G. Botte, "Optimization of Pt-Ir on carbon fiber paper for the electro-oxidation of ammonia in alkaline media," Electrochimica Acta, vol. 55, pp. 5287-5293, 2010.
Investigation of Graphene Oxide Coating for Protection against Seawater Corrosion
Authors: Kolathodi Muhamed Shareef , Voigt Victoria , Singh Gurpreet
Published: February 2020

2D materials such as graphene oxide, and Boron nitride-Carbon nanotube composite were prepared by chemical oxidation technique and coated on metallic substrates (copper foil) by slurry coating followed vacuum drying method. The anticorrosion and chemical resistivity of the coated substrates was studied quantitatively and qualitatively in 0.1 M NaCl solution using electrochemical and microscopic techniques. In general, all the coatings prevent corrosion while   graphene oxide layer reduces the corrosion rate ~1/20 times of the bare copper. The mechanism of the corrosion inhibition also discussed in detail.
(Invited) Impacts of Environmental Stress Factors on Li-Ion Battery Safety Margins
Authors: Barrera Thomas Paul , Brown Glen M
Published: February 2020

Since the mid-1990’s, many commercial, automotive, and aerospace platforms have transitioned from heritage aqueous electrolyte nickel-based energy storage batteries to lithium-ion battery (LIB) based electrical power subsystems.  For space applications, the transition from nickel-hydrogen (Ni-H2) batteries to LIB’s was accelerated by growing concerns with Ni-H2 raw materials obsolescence issues.  Although significant research efforts were undertaken to mitigate the risk of Ni-H2 raw materials obsolescence, the recurring cost of maintaining multiple Ni-H2 battery technology supply sources was prohibitive versus the longer-term benefits of supporting a deliberate transition to LIB technologies.  Other transitional market forces such as consumer demands to reduce system mass, volume and cost continue to drive the commercial electronics and automotive industries.  While it is widely recognized that the mass market for LIB’s in consumer electronics is reaching maturity, the automotive and aerospace marketplace continues to experience new technology growth opportunities.  These emerging markets are highly leveraged against economic incentives to pursue safe and reliable LIB design solutions to meet demanding customer requirements.      

Traditionally, implementing safe and reliable LIB design solutions into aerospace platforms included considerations of simplistic first-order interactions between thermal, mechanical, and electrical environmental stress factors.  However, industry experience indicates that the effect of certain synergistic stress factors on LIB performance characteristics in their service environments is a complex multi-dimensional problem.  For example, induced and natural environmental stress factors such as thermal cycling, vibration, and radiation have been shown to impact LIB battery performance and in some cases, safety margins.  Specifically, certain high-performance LIB aerospace and automotive power systems have recently been challenged to understand the principles governing lithium-ion cell thermal runaway in far greater detail than previously accepted. 

The severity of lithium-ion cell thermal runaway has created a need for identifying LIB design modifications which reduce degree of severity.  The consequences of thermal runaway have the potential to make lithium-ion chemistry an at-risk technology for some applications. To mitigate these risks, investigators from academia, government, and industry have shifted research efforts toward identifying key factors which contribute to the severity of thermal runaway.  This work focuses on identifying gaps and opportunities in achieving new paradigms for mitigating LIB safety hazards.  Challenges with current technologies to increase LIB safety margins and steps required to reach the readiness level required for successful insertion in an industrial application will also be presented.
Safety Testing in Lithium Ion Cells Comparing Thermally Stable Nanofiber-Based Separators to Traditional Polyolefin Separators
Authors: Morin Brian , Kaschmitter James , Khokhlov Pavel , Hu Carl
Published: February 2020

2.7 Ah Pouch cells of LiFePo4 and graphite were made with four different separators:

25 micron polypropylene dry process (PP)

25 micron ceramic coated polyethylene wet process (PE)

 Dreamweaver Silver 25 micron

Dreamweaver Gold 25 micron. 

Starting electrical performance was nearly identical between the cells before testing:

Hard Short:  The cells were shorted between their tabs.  The cells all performed the same, with the anode tab (4 mm tab) getting red hot, and the cells slowly heating and internally gassing until the seal broke.

Overcharge:  The cells were charged at 2C from 30% SOC.  All uncoated cells failed at 5.55 V by outgassing, while the ceramic coated PE failed at 5.9 V.  There were no flames, and the temperature rise was uniform between cells.

Hot Box:  Cells made with PP and PE/ceramic separators both had fast temperature rise and they also both experienced a catastrophic short after around 20 minutes.   DWI Silver and Gold cells maintained operational voltage for 1 hour and survived without shorting.  The short for the PE/ceramic cell occurred with onset at around 140 C, and for the PP cell at around 145 C.  Both of the DWI cells rose to 170C, the oven temperature, without experiencing a short.

Nail Penetration:  Cells made with both PP and PE separators dropped immediately to a persistent 0V along with faster and higher temperature rise (up to 115 C) than the cells made with Gold (40 C) and Silver (60 C).  The Dreamweaver cells, on the contrary, experienced only a small voltage drop of approximately 100 mV, with a slow rise thereafter as the cell discharged.  The DWI cells continued to function throughout the test and retained 2/3 of their charge and capacity after completion of the test.

Shutdown Function:  In no test was a shutdown function observed to improve the performance in any of the cells.

Figure 1
The Effects of High G Impacts on Li-Ion Batteries
Authors: Shahed Khah Nasrin , Offer Gregory James , Patel Yatish , Bhagat Rohit , Dashwood Richard
Published: February 2020

Increasing electrification of vehicles has led to a growing demand for Li-ion batteries in automotive applications. Automotive vehicles experience cyclic mechanical loads during operation, which may include; acceleration, deceleration, shock, vibration and collision. Most of these events are not severe and do not have an instantaneous effect on the battery, however it is unclear if there is a cumulative effect over time. This cumulative effect may have a significant impact on performance and safety of the battery. The collective effect of these types of mechanical events is not well characterised and there exists a gap in knowledge. This is due to the difficulty in replicating real world conditions in the laboratory.

This project focusses on the study of Li-ion batteries during static testing (3-point bend) and dynamic testing (acceleration/deceleration pulses). Several 3 point bend tests were carried out where the cell was bent to up to 30 mm and the relaxation behaviour was captured by monitoring the reduction in load over time. The electrochemical impedance of the cells was also monitored during the relaxation period and then cycled between 2.7 and 4.2 V. After each cycle, EIS was performed in order to detect impedance variation. The gradual separation of the internal structure of the cells was also captured using X-ray tomography as demonstared in fig.1. This image reveals clear separation of the internal layers at the point of contact with the side rollers and this significant separation will directly impact the performance of the cell in long term. High precision coulometry was also used as another technique to predict the cycle life of the cells besides identifying any degradation mechanism due to the severe bending. For dynamic testing cells were exposed to up to 1000 g pulses, using a drop tower (10 kJ maximum energy input). Impedance, differential capacity, and capacity of the cells were analysed before the drop, after the drop and then periodically during storage at 35oC.

Results from the high g impact tests showed that there was damage caused to the cells, but this could not be observed using EIS until after electrochemical cycling, which then manifested as an increase in the impedance of the cell. This suggests that the mechanisms are more complicated than simple damage caused by the impact, but that the impact causes damage which cannot be detected. These damages are then exacerbated by charging/discharging which then can be identified. We expect this to have significant implications for safety particularly that it may not be possible to detect damage caused by impacts without working the cells, hence this has an inherent risk. The long term effects of these incidents with regards to failure threshold are yet to be investigated.

Figure.1: CT image demonstrating clear separation of the internal layers of a pouch cell under 3 point bend loading.

Figure 1
New Understanding of Energy Distributions Exhibited during Thermal Runaway of Commercial Lithium Ion Batteries used for Human Spaceflight Applications
Authors: Yayathi Sandeep , Walker William Q. , Doughty Daniel , Ardebili Haleh
Published: February 2020

Lithium ion (Li-ion) batteries provide low mass and energy dense solutions necessary for space exploration, but thermal related safety concerns impede the utilization of Li-ion technology for human applications. Experimental characterization of thermal runaway energy release with accelerated rate calorimetry (ARC) prior to battery pack development supports safer thermal management systems. ‘Standard’ ARC setup provides means to measure the addition of energy exhibited through the body of a Li-ion cell. This study considers the total energy generated during thermal runaway as distributions between cell body and hot gases via inclusion of a unique secondary enclosure inside the ARC apparatus; this closed system not only contains the cell body and gaseous species, but also captures energy release associated with rapid heat transfer to the system unobserved by measurements taken on the cell body. Experiments include Boston Power Swing 5300, Samsung 18650-26F and MoliCel 18650-J Li-ion cells at varied states-of-charge (SOC). An inverse relationship between SOC and onset temperature is observed. Energy contained in the cell body and gaseous species are successfully characterized; gaseous energy is minimal. Significant additional energy is measured with the heating of the secondary enclosure. Regardless of manufacturer or SOC combination, a consistent range of energy release is observed when results are normalized by cell capacity (kJ/Ah). Improved ARC apparatus including a secondary enclosure provides essential capability to measuring total energy release distributions during thermal runaway.
In-Situ Scanning Electron Microscopy Observation of Lithium Dendrite Growth on Carbon Electrodes
Authors: Tang Ching-Yen , Dillon Shen J.
Published: February 2020

The formation of lithium dendrites at the anode during charging can result in capacity fade and potentially lead to internal short circuits. Adopting high capacity next-generation technologies, such as Li-air or Li-S, exacerbates this problem. Although this phenomenon has been known to be a primary safety concern and source of failure for decades, limited remedies exist to suppress dendrites growth. This partially stems from our limited understanding of the mechanism(s) governing Li dendrite nucleation and growth during cycling. While several models have been proposed, a general agreement has yet to be reached, which motivates our current work.

In this work, in-situ scanning electron microscopy was used to investigate the growth of lithium dendrites. The cell was composed of lithium cobalt oxide as the cathode, carbon film as the anode, and a Li imide salt dissolved in P13TFSI ionic liquid as the electrolyte. We were able to observe operando growth of lithium dendrites on the carbon film. The experimental configuration differs from typical Li-ion systems, since the dendrites do not grow along the field gradient, suggesting that this is not the primary source of dendrite growth. The morphologies and growth rates of lithium dendrites were characterized as a function of time and applied voltage. Additionally, the focused ion beam was utilized to cross section the lithium dendrites in-situ in order to characterize the internal morphology. The results provide new insights into the roles of surficial reactions and stresses in driving the formation of dendrites.
Optimizing and Improving the Sodium Ion Conductivity of Nasicon
Authors: Jolley Adam G , Taylor Daniel D , Wachsman Eric D.
Published: February 2020

NASICON (Na3Zr2Si2PO12) has shown promise as a solid state electrolyte for a sodium battery due to its inherent safety and relatively high conductivity.  Increasing the conductivity of NASICON to further improve the capability of a solid state electrolyte has come by way aliovalent substitution of the zirconium site in Na3Zr2Si2PO12. Both Na3.2Zr1.8M0.2Si2PO12 (M=Al3+, Fe3+, Y3+) and Na3.4Zr1.8M0.2Si2PO12 (M=Co2+, Ni2+, Zn2+) have exhibited greater bulk conductivity at room temperature than undoped NASICON. A decrease in low temperature activation energy as well as the lowered rhombohedral-monoclinic phase transformation temperature is responsible for the increased bulk conductivity of substituted NASICON.  The Co, Zn, and Ni dopants were explored more extensively as they displayed the highest conductivity of 10% doped NASICON at room temperature. By adjusting the total substitution of Co, Zn, and Ni cations, the conductivity of NASICON was optimized further. Increasing the amount of Zn+2 dopant in Na3+2xZr2-xZnxSi2PO12 resulted in reduced distortion of the lattice as it transitioned from rhombohedral to monoclinic phase, and an increase in conductivity. Ultimately the bulk ionic conductivity of 20% Zn-doped NASICON is among the highest ever reported.
Solid State Li Ion Batteries with Monocarba-Closo-Decaborate Solid Electrolytes
Authors: Ware Nicholas , Tang Wang Si , Udovic Terrence John , El Gabaly Farid , Stavila Vitalie , Talin Albert Alec
Published: February 2020

Solid state rechargeable batteries with high energy and power density as well as safety, reliability and long cycle life remain a long standing goal for the energy storage community.  While many solid electrolytes have recently been demonstrated with ionic conductivities approaching those of liquid electrolytes at room, few have been integrated into full batteries with competitive power performance.  Recently, we discovered a novel class of superionic solid electrolytes, whose facile cation conduction pathways are enabled by the spacious, vacancy-rich, interstitial network created by a sublattice of polyhedral, orientationally mobile, monocarba closo-borate anions and which form salts with alkali metals, LiCB11H12
and LiCB9H10 [1, 2]. These electrolytes exhibit conductivities of ~10-5 S/cm at room temperature and ~0.03 S/cm at 345 C. In this talk we will describe the fabrication and testing of complete batteries consisting of thick film LiCoO2 cathodes with theoretical capacity of ~1.5 mAhrs/cm2 and metallic Li anodes.

1. W. S. Tang, A. Unemoto, W. Zhou, V. Stavila, M. Matsuo, H. Wu, S. Orimo, and T. J.   

    Udovic, Energy Environ. Sci., 2015, doi: 10.1039/c5ee02941d.

2. W. S. Tang, M. Matsuo, H. Wu, V. Stavila, W. Zhou, A. A. Talin, A. V. Soloninin,  R. V.

    Skoryunov, O. A. Babanova, A. V. Skripov, A. Unemoto, S. Orimo, and T. J. Udovic, Adv.  

   Ener. Materials, in review.
(Invited) Can Basic Research in Academia Predict Battery Field Failures?
Authors: Jeevarajan Judith A
Published: February 2020

Cell and battery field failures can occur in a number of ways.  Cause of failures can vary from inadequate cell and battery safety controls to poor manufacturing quality.  Oftentimes, basic research in academia is focused on improving materials to obtain higher specific capacity or power density.  The practical issues of failure scenarios created due to scaling up from a lab scale to a large Mega or giga Watt energy storage application are seldom mimicked or studied.  This paper will discuss the areas that have gaps in safety research with a focus on lithium-ion battery chemistry.
Structure and Electrochemical Properties of Na0.44MnO2 As Positive Electrode Material in Sodium Ion Battery
Authors: Man Tran Van , Huynh Nguyen Le Thanh , Nguyen Van Hoang , Phung LE My Loan
Published: February 2020

At the present, most the electronic portables are operated by Li-ion batteries (LIB), moreover LIB have also been desired to apply in the large-scale as hydride electric vehicles, smart grid system because of its high density energy and high voltage. The development of LIB forecasts a growing demand for lithium supplies. In order to solve the problem of lithium raw resource, sodium is proposed as an alternative energy storage to replace the LIB in the future because of the several reason: abundance of sodium resource, low cost of sodium raw material and similar properties chemistry of lithium.

Na0.44MnO2 have been attracted as novel cathode materials for sodium-ion batteries due to low cost, high capacity and good performance. This work aimed to prepare the cathode material Na0.44MnO2 by solid state reaction form three different manganese precursors such as: MnCO3, Mn(AcO)2 and MnO2 (obtained by electrolysis of MnSO4 solution). The cyclic voltammetry curve presents the multi-peaks redox corresponding to the complex insertion/extraction of sodium ions. The sample Na0.44MnO2, prepared by Mn(AcO)2 precursor, exhibits both the excellent cycle stability (120 mAh/g at C/10) and high charge/discharge rate capability in the range 2-4 V (vs. Na+/Na). Furthermore, the ex-situ Raman Spectroscopy and Diffraction Rayon X studies are also reported the evolution of lattice parameters during discharge process that evidently confirmed the existence of transition-phases.

 Keywords: cathode materials, Na0.44MnO2, sodium-ion batteries, Raman spectroscopy
Electrochemical Properties of Li3V2(PO4)3/C Cathode Materials Prepared Via Sol-Gel Process
Authors: Choi Seung-Woo , Kim Min-Young , Yang Seung-Hoon , Kim Da-Hye , Noh Tae-Hyoung , Kim Ho-Sung , Lee Moo Sung
Published: February 2020

It is reported that LVP(Li3V2(PO4)3) material has a good advantage for safety property, but this material showed low electric conductivity. Therefore, many researches have been performed to improve the electrochemical properties of LVP material by reducing of particle size with cation doping and carbon coating, etc. In here, we prepared nano-sized LVP/C composite materials with a high purity using a sol-gel method including a carbon coating and heat treatment process. As a result, nano LVP/C powders were obtained with calcination temperature of 750 ~ 900 °C. and the LVP/C material cells showed about 130 mAh/g in the range of 3.0 V to 4.3 V and 170 mAh/g in the range of 3.0 V to 4.8 V, approaching to the theoretical capacity. We will introduce lattice parameters calculated by Reitveld analysis and C-rate capacity with cycles on the samples in detail.