bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Photoelectrochemical Investigation of Ta3N5 Films on TCO Substrates Synthesized Via Atomic Layer Deposition for Photocatalytic Water Splitting
Authors: Hamann Thomas
Published: February 2020

Solar driven photoelectrochemical (PEC) water splitting is a promising method to store solar energy in chemical bonds. Tantalum nitride (Ta3N5) has recently emerged as a promising candidate for PEC water splitting. Most of the studies on Ta3N5 begin with a similar synthetic route, consisting of an initial oxidation of Ta(0) metal to Ta(IV), followed by  ammonolysis at elevated temperatures ( > 850 °C). Despite the simplicity of this method, there are also several drawbacks. Importantly, the high temperature ammonolysis limits the utilization of transparent conductive oxide (TCO) substrates which are necessary for fundamental photoelectrochemical measurements. In addition, lack of viable TCOs thwart use of Ta3N5 as the top electrode in a tandem PEC cell.

As a solution to the above problems, we will present the synthesis of Ta-doped TiO2 (TTO) as a TCO substrate via atomic layer deposition (ALD) which we found to be stable in reducing atmospheres. ALD was also used to directly deposit thin films of Ta3N5 on TTO. While initial attempts produced as-deposited films are primarily amorphous TaOxNy, these films can be nitridized to Ta3N5 at far more moderate conditions compared to all previous reports and ALD–deposited tantalum oxide analogue films. The photoelectrochemical properties of the TTO/Ta3N5 films were investigated and the PEC water oxidation performance was analyzed. The excellent material control reported here allowed for a detailed material structure – function relationship to be determined and a path to improved performance elucidated. Initial results of a modified procedure, including ALD precursor and temperature variations, which allowed the direct synthesis of crystalline Ta3N5 on TTO substrates, will also be presented.
(Invited) Hierarchical Inorganic Assemblies for the Photocatalytic Reduction of CO2 By H2o
Authors: Frei Heinz
Published: February 2020

The multi-electron processes of CO2 reduction and H2O oxidation, which constitute the essential reactions of sunlight to fuel conversion (artificial photosynthesis) require efficient coupling of light absorber and catalyst. Using all-inorganic heterobinuclear units such as ZrOCo anchored on high surface area silica, we have developed photodeposition methods for the directional assembly of nanometer sized catalyst clusters for H2O oxidation or CO2 reduction with proper coupling to the binuclear light absorber. Copper oxide nanoclusters were assembled adjacent to the Zr acceptor sites of the heterobinuclear unit, and light driven reduction of CO2 upon excitation of the ZrOCo unit demonstrated. Illumination of the ZrOCo chromophore coupled to a metal oxide nanocatalyst for H2O oxidation affords closing of the photocatalytic cycle in the absence of sacrificial agents. Time resolved FT-IR spectroscopy provided detailed mechanistic insight into the multi-electron reactions of H2O oxidation and CO2 reduction on the metal oxide catalyst surfaces under reaction conditions, with surface intermediates and their kinetics uncovered for the first time.

To achieve CO2 photoreduction by H2O under product separation on the nanoscale, Co3O4-SiO2 core-shell nanotubes were developed in which the inner surface acts as efficient water oxidation catalyst while the nanoscale silica layer with embedded molecular wires serves as a proton conducting, gas impermeable separation membrane with tight control of electron transport. Completing the photocatalytic cycle on the nanoscale seeks to minimize side reactions and efficiency degrading transport processes. Characterization of the assembly by transient spectroscopy and photoelectrochemical measurements will be discussed.

References

Zhang, M.; de Respinis, M.; Frei, H. Nature Chem.
2014, 6, 362.

Kim, W.; Yuan, G.; McClure, B. A.; Frei, H. J. Am. Chem. Soc.
2014, 136, 11034.

McCure, B. A.; Frei, H. J. Phys. Chem. C
2014, 118, 11601.

Kim. W.; Frei, H. ACS Catal.
2015, 5, 5627.

Yuan, G.; Agiral, A.; Pellet, N.; Kim, W.; Frei, H. Faraday Discuss.
2014, 176. 233.

Edri, E.; Frei, H. J. Phys. Chem. C
2015, 119, 000.
A Differential Electrochemical Mass Spectrometric (DEMS) Study of the Electrocatalytic Reduction of CO2 on Cu and Au/W Electrode Surfaces
Authors: Javier Alnald , Baricuatro Jack Hess , Kim Youn-Geun , Soriaga Manuel P
Published: February 2020

This work describes the employment of differential electrochemical mass spectrometry (DEMS) to investigate selectively pre-adsorbed reactants and (postulated) intermediates as a supplementary experimental approach in the study of the reaction mechanism of the Cu-catalyzed electrochemical reduction of CO2. The results show the following empirical inferences: (i) CO is one of the first products of CO2 reduction, as well as the first intermediate in more advanced reactions that include formation of hydrocarbons and oxygenates; this is in conformity with the (almost) unanimously held view. (ii) Formaldehyde, HCHO, is not a precursor for C=C double-bond formation. (iii) HCHO is an intermediate for the production of methane and ethanol. (iv) Methane and ethanol can be generated from adsorbed CO via two ways: one requires a theoretically postulated surface species, CO protonated on the C atom, and the other involves adsorbed HCHO, constituted after the rate-limiting CO-protonation step. (v) The generation of CH4 and CH3CH2OH from CO has a much higher activation barrier than from HCHO; not unexpected since the formaldehyde intermediate is formed after the slow Cu–OCH formation and, consequently, is not highly activated.

This work also presents a study based on DEMS that tested the theoretical prediction suggesting the viability of a bimetallic near-surface alloy (NSA) made up of Au and W as a CO2-reduction electrocatalyst selective towards the formation of methanol as a product, away from methane, ethylene or ethanol typically produced using Cu as the catalyst. At an overlayer NSA that consisted of n monolayers (ML) of Au on a polycrystalline W electrode, W(pc)-n[(1×1)-Au], no methane, methanol, ethylene or ethanol were detected when the coverage of Au was at submonolayer (n = 0.5) or multilayer (n ≥ 2) coverages. However, when the overlayer contained only 1 ML of Au, methanol was generated exclusively. The anticipated CH3OH-product-selectivity of the W(pc)-(1×1)-Au NSA has thus been (qualitatively) confirmed. The CH3OH-selective activity was 52 µA cm-2 for a Faradaic efficiency of 0.50%; the bulk of the current was expended towards H2 evolution and, since the topmost layer was Au, most likely in the production of CO and formates that cannot be studied by DEMS.
Electrochemical CO2 Reduction: Screening of Material Libraries and Improving Selectivity of Cu By Mixing It with Co
Authors: Grote Jan-Philip , Zeradjanin Aleksandar R. , Cherevko Serhiy , Savan Alan , Breitbach Benjamin , Ludwig Alfred , Mayrhofer Karl J.J.
Published: February 2020

Using CO2 and converting it into useful products or even fuels is considered as a “dream reaction”. However even after over 30 years of research in the field of electrochemical CO2 reduction the “dream” didn’t come true and still remains a scientific and technical challenge. Two main applications can be considered for the electrochemical CO2 reduction: (1) The operation as storage technology to compensate the unavoidable energy fluctuations produced by renewable energy source like wind or sun and (2) the syntheses of valuable products like ethylene. Whilst in gas-phase heterogeneous catalysis the conceptual understanding about converting CO2 into fuels and the applied processes are well developed, electrochemical CO2 reduction is still in a stage where fundamental research is inevitably necessary to prove feasibility before large-scale implementation. On the contrary distinct advantages are the direct use of electrical energy, a potential dependent and therefore customizable product distribution and operation at ambient pressure and temperature. 

Main reasons for a so far not realized commercial application are (1) the low selectivity for valuable products on hydrocarbon producing electrodes and thereby a costly product separation, (2) the low energy efficiency as a cause of high overpotential on the working electrode and (3) the oxygen evolution as counter reaction, that also shows high overpotential and in addition to that catalyst degradation by dissolution. 

In order to address the fundamental understanding of the reduction processes on various types of material combinations, we have developed an electrochemical technique that enables (1) screening of thin-film material libraries with different experimental parameters, (2) investigating catalyst activity and stability of electrodes in parallel by inductively coupled plasma mass spectrometry (ICP-MS) and (3) analyzing the selectivity of catalysts for certain products via online electrochemical mass spectrometry (OLEMS).

First results utilizing this approach will be presented; the focus will be in particular on the shift in selectivity towards C2 products of the electrochemical CO2 reduction on Cu-Co thin film composition spread samples at ambient temperature and pressure. Due to a high resolution composition analysis we were able to find a composition where production of C1 species is suppressed, while in return C2 production is enhanced. Utilization of this technique deepens understanding of fundamental processes and shows its high potential for improving performance of electrochemical CO2 reduction.
Possible Use of Yttria-Stabilized Zirconia for Potentiometric Sensors at Room Temperature
Authors: Szendrei Alex Laurence , Virkar Anil V. , Sparks Taylor
Published: February 2020

A yttria-stabilized zirconia (YSZ) tube with platinum electrodes was used for measurement of potential with one electrode exposed to air and the other to H2-H2O gas mixtures. Measurements were conducted over a temperature range from 30°C to 475°C using two different meters, one with input impedance of 10 GΩ and the other with input impedance > 200 TΩ. With the high impedance meter (electrometer), a voltage of 0.93 V was measured at 30°C, while it was much lower using the low impedance meter. Above ~177°C readings from both meters converged. From the measurements, the actual cell voltage and the net cell resistance including all polarization resistances were estimated. Above 275°C, the measured voltage was in agreement with the expected Nernst voltage. At lower temperatures, the voltage even with the electrometer was lower than the calculated Nernst voltage indicating that H2-H2O gas phase mixture did not reach equilibrium. Electrochemical impedance spectra (EIS) were obtained. From the EIS spectra, the ohmic resistance was obtained. Above 75°C much of the cell resistance is attributed to electrode polarization.
(Invited) Triboelectric Nanogenerators for Self-Powering Small Electronics
Authors: Kim Sang-Woo
Published: February 2020

Energy harvesting systems based on triboelectric materials are in great demand, as they can provide routes for the development of self-powered devices which are highly flexible, stretchable, mechanically durable, and can be used in a wide range of applications. Further recently smart systems met a large success. At the origin of the internet of things, they are a key driving force for the development of wireless, sustainable and independent autonomous smart systems. The autonomy is critical and despite all the progresses in low power electronics and battery, energy harvesters are becoming increasingly important. Thus harvesting mechanical energy is essential as it is widespread and abundant in our daily life environment. Among harvesters, flexible triboelectric nanogenerators exhibit good performances and are easy to integrate which make it the perfect candidate for many applications, and therefore crucial to develop. In this talk, I will address the importance of nanogenerators as well as the recent advances in power generation through triboelectric nanogenerators with the power generation mechanism. Furthermore recent research and design efforts for enhancing the power generation to commercialize nanogenerators for self-powering portable and wearable devices with low power consumption will also be presented.
A Paper-Based Electrochemical Sensor Array for Detection of Hydrogen Peroxide
Authors: Shamkhalichenar Hamed , Choi Jin-Woo
Published: February 2020

A sensitive and rapid detection of hydrogen peroxide (H2O2) is important in biomedical, food, and environmental analysis. The enzyme-based electrochemical detection of H2O2 may provide simple, accurate, and rapid process; however, due the thermal and chemical deformation of enzymes during the fabrication process, these sensors may suffer from instability [1]. Recently, some particles which has electrocatalytic properties toward H2O2 has been employed to develop electrochemical sensors.  Of these, iron oxide (Fe3O4) and copper oxide (CuO) nanoparticles have shown good electrocatalytic properties toward H2O2 [2, 3]. However, one common drawback of these sensors is lack of selectivity owing to the fact that these catalysts shows electrocatalytic properties toward various analytes in the solution. Here, we present a novel paper-based electrochemical sensor based on modified carbon nanotube electrode, which can reduce the matrix effect in multi-analyte solutions. Paper-based sensors have become of great interest for fabricating inexpensive, simple, and disposable sensors. Carbon nanotube electrode ink has been modified using CuO and Fe3O4, and an electrode array made of modified and bare carbon ink solutions is developed by utilizing screen-printing of carbon ink solutions on paper. Figure shows the developed paper-based sensor array design. Moreover, a multichannel potentiostat circuit has been developed in order to investigate the amperometric response of the sensor array on H2O2 solution. The potentiostat can control three working electrodes independently, and it is also working with a USB port as power source. Since these modified electrodes show a unique response to different electroactive species, the results can be interpreted using a statistical method to compromise the interference from other electroactive species in the solution. Further, solutions with various concentration of H2O2 and interfering species has been tested using the portable potentiostat in order to assess the matrix effect originated from the interfering species in H2O2 detection.

References

[1] M. Song, S. Hwang and D. Whang, “Non-enzymatic electrochemical CuO nanoflowers sensor for hydrogen peroxide detection,” Talanta, vol. 80, no. 5, pp. 1648-1652, 2010.

[2] M. Lin and H. Leu, “A Fe3O4-based chemical sensor for cathodic determination of hydrogen peroxide,” Electroanalysis, vol. 17, no. 22, pp. 2068-2073, 2005.

[3] X. Miao, R. Yuan, Y. Chai, Y. Shi and Y. Yuan, “Direct electrocatalytic reduction of hydrogen peroxide based on Nafion and copper oxide nanoparticles modified Pt electrode,” Journal of Electroanalytical Chemistry, vol. 612, no. 2, pp. 157-163, 2008.

Figure 1
A Laminar-Flow Based Microfluidic Microbial Three-Electrode Cell for Biosensing
Authors: Yang Bin , Li Feifang , Zhang Xingwang , Li Zhongjian
Published: February 2020

Microbial three-electrode cells (M3C) have been widely used as a promising platform for developing biosensors and studying electrochemically active bacteria (EAB). Compared to conventional microbial two-electrode cells (e.g. microbial fuel cells and microbial electrolysis cells), M3Cs can offer more stable and better defined electrochemical environments for various research purposes. This work focuses on developing a microfluidic M3C with micro-liter scale volume by using soft-lithography technology, which has comparable performance as the conventional bench scale M3Cs. In this microfluidic M3C with a build-in three electrode system, laminar flow was exploited to separate the reference electrolyte (0.1 M KCl) from the medium without hindering ion exchange. With the stable and controllable working electrode potential, this device was able to provide a well-defined electrochemical environment for G. sulfurredecens respiration on the electrode. Due to the micro-liter scale volume and a short hydraulic retention time (HRT), fast responses to ferric citrate and formaldehyde with a good reproducibility were achieved. Furthermore, a good linear relationship between the output signal (peak area) and chemicals concentrations was obtained. The microfluidic M3C developed in our work would provide researchers in related areas a versatile platform for biosensor and fundamental EAB study.
Rapid Detection of Pathogens By a 3D Biomolecular Filter and Automated Biosensor Measurement System for Liquid
Authors: Du Songtao , Horikawa Shin , Liu Yuzhe , Chai Yating , Hu Jiajia , Chin Bryan A
Published: February 2020

A new method of rapid detection of pathogens by 3D biomolecular filtering and automated indexing plate measurement has been demonstrated. In this process, a liquid containing pathogens is passed through a 3D biomolecular filter composed of planar arrays of MagnetoElastic (ME) biosensors held by a magnetic field.  This filter captures specific target pathogens (in our demonstration case, Salmonella) in the liquid as it passes over the filter. The experiment will be under different Salmonella concentrations, different flowing rate, different number of ME biosensors and different solution volume. Capture of the pathogens is by specific biomolecular recognition, not size exclusion as with traditional filters. After the entire liquid has passed over the filter, the magnetic field is shut off and the individual biosensors collected and dried.  The biosensors are then placed on an indexing plate consisting of an array of rectangular cavities approximately 10% larger in size than the ME biosensors.  A vibrating table is used to vibrate the ME biosensors into motion until each cavity of the plate is occupied by a single ME biosensor. The biosensors are then measured by sequentially positioning the sensors under a surface scanning detection coil for measurement of the final resonance frequency of the biosensors using an automated translation system. In this manner, a single sensor can be measured in less than 2 seconds with 1000 sensors being measured in less than 30 minutes.
Electrochemical Dissolution of a Microneedle System for Controlled Drug Release in Smart Devices
Authors: Anderson Ashleigh , Davis James
Published: February 2020

The majority of conventional controlled release technologies tend to be based around encapsulant systems in which a polymeric binder or gel typically responds to changes in the local environment in which the delivery device has been placed. The contents are often released when the particle, capsule, film or droplet is exposed to the appropriate physico-chemical trigger (typically a change in pH) with the time-release-dose delivery characteristics controlled through manipulation of the encapsulant formulation. In this communication, the adaptation of this core strategy for use in the next generation of transdermal microdevices or smart patch is explored. The core rationale of this work relates to the development of microneedle patches through which a drug could be transported across the skin barrier upon activation by an appropriate electrochemical trigger.

The microneedle in this case serves as the entry point through the strateum corneum whilst acting as a physical barrier to the transport of the drug from a reservoir within the patch.  Upon activation, the microneedle dissolves thereby allowing the release of the therapeutic agent as indicated in Figure 1A,B.

The methodology proposed herein focuses on the ability to control the dissolution of the conductive composite microneedle through an application of a specified potential trigger. Central to this approach is the design and fabrication of a novel nanostructured conductive film based on a composite of carbon nanoparticles and cellulose acetate phthalate (CAP). This is created through the solvent cast method onto a silicone microneedle template shown in Figure 1C.  Under normal conditions, the conductive coating remains intact but, upon imposing a reducing potential on the carbon composite layer, the local pH is increased which results in the solubilisation of the pH sensitive CAP binder components. The latter is the structural glue that holds the microneedle together and thus the subsequent swelling effectively leads to the dissolution of the microneedle architecture and the release of the drug. The presentation covers three aspects: the design and characterisation of the carbon composite microneedles, the ability to electrochemically manipulate the structural integrity of the needles and the ability to effect the controlled release of model drugs such as codeine, methotrexate and fentanyl.

Figure 1
Synthesis and Characterization of Gold Nanostructures and Their Activity Against Dopamine
Authors: Silva Juan Francisco , Ramirez Sara , Silva Nataly , Oyarzun Maria Paz , Pavez Jorge
Published: February 2020

This research aims to study the incorporation and effective containment of gold nanostructures on a substrate electrode applied to electrochemical sensors for the detection of dopamine. gold nanoparticles (AuNPs) was synthesized using the protocol developed by Turkevich [1]. Additionally gold nanorods (AuNBs) were obtained using the method described by growth Nikoobakht [2]. These nanostructures have been incorporated into a metal substrate mediated self-assembled monolayers (SAMs) for a 4-mercaptopyridine (4MPy), which allows the confinement and effective communication of the nanostructure. Furthermore, to evaluate the anisotropic effect against dopamine response.

Chemical and morphological characterization system were used: X-ray photoelectron spectroscopy (XPS), the atomic force microscopy (AFM) (fig 1A), the scanning tunneling microscopy (STM) (fig 1B), and electron microscopy transmission (TEM). Additionally, for the functional characterization of the system, the cyclic voltammetry was used to determine: 1. The crystallographic orientation of the gold substrate; 2. The electrochemically active bare gold substrate and the nanostructures incorporated area, 3. quimidesorción the SAMs; 4. The electrochemical redox response of two probes K3Fe (CN)6 and Ru (NH)6Cl3 to evaluate the anisotropic effect.

Finally it was studied by voltammetric square wave detecting dopamine by preparing a calibration curve, which shows that as the concentration of neurotransmitter increases the signal, ie, the peak height ( Ip), it is proportional to the concentration, in both systems the same phenomenon occurs, however, for the device AuNBs formed with has a detection potential differing from the potential detection of a gold surfacer.

Acknowledgements: Proyectos Fondecyt Nº 1131062 y 1140192

references: 

1.Kimling, J., M. Maier, B., Okenve, Kotaidis V., Boleta, H., Plech *A., Turkevich. (2006). new method for synthesis of gold nanoparticles. J phys Chem 110, 15700.

2.Nikoobakht, B., Mostafa, A. El-Sayed*. (2007). Preparation and Growth Mechanism of Gold Nanorods (NRs) Using Seed-Mediated Growth Method. Chem Mater 15, 1957.

Figure 1
Highly Sensitive and Simultaneous Determination of Hydroquinone and Catechol at an Optimized Activated Glassy Carbon Electrode
Authors: Ahammad A J Saleh , Ullah Md. Aman , Hoque M. Mominul , Akter Tania , Mamun Abdullah Al
Published: February 2020

Glassy carbon electrode (GCE) was activated with four different electrochemical activation process: (1) by applying a fixed potential of +1.7 V for 400 s (FP-AGC); (2) by cycling the potential between +2.0 and −0.3V for 15 cycles at 0.1 V/s (CP-AGC); (3) by applying a fixed potential of +1.7 V for 400 s followed by cycling the potential between +2.0 and −0.3V for 15 cycles at 0.1 V/s (FC-AGC) and (4) by applying +1.7 V for 400s followed by -1.0 V for 60s (DP-AGC). All four activated GCEs showed catalytic activity and reversibility toward the oxidation of both hydroquinone (HQ) and catechol (CT) in 0.1 M phosphate buffer solution (PBS, pH 7.0). However, a remarkable signal enhancement of HQ and CT was obtained at DP-AGC, which is considered as optimized activated GC. By using this optimized AGC we have developed a highly sensitive and selective electrochemical method for the determination of HQ and CT simultaneously. The redox responses from the mixture of HQ and CT were easily resolved at DP-AGC. The detection limits for HQ and CT were calculated to be 15.0 and 10.0 nM respectively. The optimized AGC was successfully examined for real sample analysis with tap water and it showed a stable and reliable recovery data with reproducibility.
Electrodeposition of Dendritic Ni-Co Onto High-Voltage Electrodes of Electrostatic Particulate Matter (PM) Sensors
Authors: Copenhaver Katherine , Allmendinger Klaus , Beckert Michael , Boettcher Michael , Fitzpatrick Joseph , Henderson Brett , Nadler Jason , Woo Leta
Published: February 2020

Particulate matter (PM) or soot sensing technologies are needed for feedback and control of exhaust after-treatment systems to meet increasingly stringent environmental regulations. A novel low-cost electrostatic PM sensing approach has recently been developed based on a concentric electrode design with a central cylindrical high-voltage electrode surrounded by an inner baffle that serves as the ground/negative terminal. The sensing principle is not completely understood, but seems to rely on capturing naturally combustion charged particles on electrode surfaces where a delay in sensor startup time occurs during initial testing. The influence of three-dimensional dendritic Ni-Co coatings on PM sensor performance was examined. Nickel and cobalt were co-electrodeposited on cylindrical stainless steel substrates from an electrolytic bath using a square waveform cathodic current. The effect of altering the applied current density and the number of current cycles on the height and spacing of dendritic features was monitored in attempts to correlate surface morphology to the performance of the materials as PM sensors. Coatings were characterized using scanning electron microscopy and confocal laser microscopy, and Ni-Co coated cylinders were used as the central high-voltage electrodes of electrostatic PM sensors to determine the effect of different microstructures on sensor performance. The coated electrodes demonstrated an improvement in startup time for an optimized coating morphology when compared to bare control electrodes. The surface features of the dendritic Ni-Co coatings are believed to alter the interaction of PM with the high-voltage electrode and can induce a faster response of the sensor when optimal electrodeposition conditions are employed.
Modeling and Simulation of Thermal Runaway in Cylindrical 18650 Lithium-Ion Batteries
Authors: Melcher Andreas Markus , Lei Boxia , Ziebert Carlos , Rohde Magnus , Seifert Hans Jürgen
Published: February 2020

The thermal runaway of a single Li-ion battery (LIB) in larger battery package is the worst case scenario which must be avoided under all circumstances. In this work the electrochemical-thermal model for a LIB based on porous electrode theory is extended with contribution coming from exothermic side reactions to model the abuse mechanisms in Li-ion batteries with respect to the temperature which could lead to a thermal runaway. The electrochemical-thermal model is extended with several new contributions which occur in several temperature regimes. In detail the heat source in the corresponding heat equation is extended  with the heat generated by various exothermic reactions, for example at the surface-electrolyte interface at temperatures in the interval T=[T1, T2],  reactions between anode resp. cathode and the electrolyte between temperatures in the interval T=[T3, T4]  and the destruction of the electrolyte above the temperature T>T5, where T1<T2 ≤T3<T4 ≤T5. These extensions will be modeled with a solid fuel or a constant fuel model as simplification coming from combustion theory. For this extended model simulations are performed for specified current profiles and exterior temperature profiles to simulate an oven trial and cell cycling.  In the simulations a cylindrical 18650 LIB is investigated with a LiCoO2 cathode.  The purpose of the simulations is to compute the temperature-field during the time evolution of a thermal runaway, therefore the cross section in horizontal and vertical direction are considered as well as the one-dimensional temperature profiles along these directions. Finally the time evolution of the overall mean cell temperature T is used to classify the different stages of a thermal runaway in a T-dT/dt-plot. The results will be compared with experimental ARC-measurements in pure oven experiments and cycling experiments.
Population Balance Model of Lithium Ion Batteries
Authors: Tahmasbi Amir Abbas , Kadyk Thomas , Eikerling Michael
Published: February 2020

We develop a physical-statistical model of particle-based battery electrodes in Li ion batteries. Graphite particles and metal oxide crystallites are the active components in the battery electrodes. During charging/discharging cycles, electrodes experience reversible changes and they go through irreversible structural transformations. Our hierarchical approach employs a particle population balance model based on Fokker-Planck theory. It relates structure-transforming processes at the particle level to macroscopic changes in physicochemical properties and performance. At the particle level, the model accounts for particle activation or deactivation during charging or discharging. Moreover, at the negative electrode, it incorporates formation and growth of the solid electrolyte interphase (SEI), as well as the formation of cracks in the SEI and growth of the SEI area. At the positive electrode, it accounts for the kinetics of crystallite dissolution and isolation. These processes determine changes in the statistical particle density distribution function. So far, we have incorporated an SEI growth model into the population balance model. Our initial results show that the SEI thickness increases from 30 nm to 80 nm after 500 cycles. In a future step, we will include formation of cracks in the SEI and crack-initiated growth of the SEI surface and we will link these changes to the battery performance parameters e.g. capacity fade and power fade.
The Redox Potential and Chemical Stability of Li7P3S11 Using VASP Calculation
Authors: Doh Chil-Hoon
Published: February 2020

Study on Li7P3S11 material was carried out by ab initio calculation using the Vienna ab initio Simulation Package (VASP)[1]. Li7P3S11 was known as a super-ionic conductor (5.4 mS/cm at 25°C) to be a solid-electrolyte of all-solid-state lithium batteries. Two different crystal structure of Li7P3S11 were reported by Onodera (2010) and Tatsumisago (2007) with slight difference on atomic positions. Between total energies of VASP calculation on two structures, Tatsumisago’s structure had slightly more stable energy (Etotal –92.573 eV). Among Li7P3S11, Li3PS4, Li4P2S6 and Li4P2S7, the formation potential of Li7P3S11 was the highest value of 2.216 V(Li/Li+) to be the most stable material. Chemical reactivity of Li7P3S11 material toward moisture to be Li7P3O11 had the reaction energy of –0.34 eV. Li+ conduction of Li7P3S11 take place through vacancy and interstitial diffusion pathways. Xiong (2014) reported on the formation potential of Li7-1P3S11. Evaluated result of the formation potential of Li14-1P6S22 was also appeared similar to Xiong’s results. Formation potentials of Li14+1P6S22 were also evaluated for four different interstitial sites. Site(III) denoted at Xiong’s report had 0.643 V(Li/Li+) to be the most easy accommodation of Li+ ion. Patterns of the total density of states (TDOS) of Li14+xP6S22 (x=1,0,-1) were not so different and shown ~3.5 eV by the Hyed-Scuseria-Ernzerhof (HSE) hybrid functional and ~2.1 eV by GGA to be electronic insulator.

[1] Kresse,G.; Hafner, J. Phys. Rev. B, 47 (1993) 558; 49 (1994) 14251.

Figure 1
Modeling Co-Extruded Cathodes for High Energy Lithium-Ion Batteries
Authors: Cobb Corie Lynn
Published: February 2020

Utilizing an existing macro-homogeneous porous electrode model developed by John Newman, this talk presents the potential energy density gains that can be realized in lithium-ion battery electrodes fabricated with co-extrusion (CoEx) technology. CoEx uses carefully engineered fluidic channels to cause multiple streams of dissimilar fluids to impart shape to one another. The result is a high-speed, continuous deposition process that can create fine linear structures much smaller than the smallest physical feature within the printhead. By eliminating the small channels necessary for conventional extrusion and injection processes, CoEx is able to deposit highly loaded and viscous pastes at high line speeds under reasonable operating pressures. The CoEx process is capable of direct deposition of features as small as 10 μm with aspect ratios of 5 or greater, and print speeds > 80 ft/min.

We conduct an analysis on two-dimensional cathode cross-sections in COMSOL and present the electrochemical performance results, including calculated volumetric energy capacity for Lithium Nickel Manganese Cobalt Oxide (NMC) co-extruded cathodes, in the presence of a lithium metal anode, polymer separator and ethylene carbonate–diethyl carbonate (EC:DEC) liquid electrolyte. The impact of structured electrodes on cell performance is investigated by varying the physical distribution of a fixed amount of cathode mass over a space of dimensions which can be fabricated by CoEx. By systematically varying the thickness and aspect ratio of the electrode structures, we present an optimal subset of geometries and design rules for co-extruded geometries. Modeling results demonstrate that NMC CoEx cathodes, on the order of 125-200 µm thick, can garner an improvement in material utilization and in turn capacity through the addition of fine width electrolyte channels or highly conductive electrode regions. We also present initial experimental results on CoEx NMC cathode structures.

The information, data, or work presented herein was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000324.
A Combined First-Principles and Experimental Investigation of the Li7P3S11 Superionic Conductor
Authors: Chu Iek-Heng , Nguyen Han , Lin Yuh-Chieh , Wang Zhenbin , Xu Zihan , Hy Sunny , Deng Zhi , Meng Shirley Ying , Ong Shyue Ping
Published: February 2020

Rechargeable all-solid-state lithium-ion batteries utilizing a fast lithium superionic conductor electrolyte (SCE) has the potential to revolutionize energy storage by providing an inherently safer, less flammable alternative to traditional organic electrolyte-based batteries.  Synthesized from 70Li2S:30P2S5 glass-ceramic, the Li7P3S11 metastable crystal is a promising SCE that exhibits very high ionic conductivity of 17 mS/cm, comparable to those of liquid electrolytes. In this work, we present a combined computational and experimental study on this compound. We find that though Li7P3S11 is predicted unstable at zero temperature, it becomes stable at 630 K when vibrational entropy contributions are accounted for, in excellent agreement with experimental measurements. We will also report on the calculated surface energies and Wulff shape of the Li7P3S11 crystal. Finally, we demonstrate that ab initio molecular dynamics (AIMD) simulations predict Li7P3S11 to have a significantly higher room-temperature ionic conductivity than previously reported, suggesting that there is significant scope for the further optimization of this material.
(Invited) Swelling and Elastic Deformation of Lithium-Silicon Electrode Materials
Authors: Baker Daniel R , Verbrugge Mark W , Bower Allan F
Published: February 2020

Lithium-battery electrodes made from silicon  increase volume by a factor of four when charging from a de-lithiated to fully lithiated state, but by charging and discharging slowly enough, stresses can be reduced, which avoids stress damage to the electrode. We provide a mathematical description comprehending the relevant solid mechanics (i.e., stress and strain) and diffusion processes so as to describe highly expanding battery electrode materials and determine the maximum current at which lithium-silicon can be charged and avoid exceeding the material yield stress. An approximate metric for acceptable stress levels is that they are less than 1% of the elastic modulus. At these low stress levels, infinitesimal strain theory can be used for the computations. The rate of charge and discharge that keeps stress below this level depends on values for the elastic modulus, the Poisson ratio, the lithium diffusion coefficient, the particle size, the open-circuit potential of the material, and several other parameters whose values are generally concentration dependent. The derived formulas are analytic and straightforward to apply (e.g., they can be employed in conventional spreadsheet software) and can be used to assess potential new materials, design better electrodes, and improve operating strategies.

Example outputs from the mathematical model can be seen in the two figures below.  The upper figure provides calculated results for the open-circuit potential, modulus, particle radius (left ordinate) and perturbation parameter (right ordinate) as a function of time (or average fraction of filled lithium sites y
0).  During charge, the potential and the modulus (stiffness) decline monotonically, the radius increases monotonically, and the perturbation parameter is a complicated function of y
0.  Histories of the radial, hydrostatic, and tangential stresses as a function of time (or average fraction of filled lithium sites y
0) and at radial positions r/a = 0, 0.5, and 1 are provided in the lower figure.  Note that the abscissas are identical.

Figure 1
A Simulation Framework for Battery Safety Modeling
Authors: Marcicki James , Bartlett Alexander , Yang Xiao Guang , Mejia Valentina , Zhu Min , Chen Yijung , L'Eplattenier Pierre , Caldichoury Inaki
Published: February 2020

Increased utilization of Lithium-ion batteries for a variety of applications is driving the need for advanced simulation tools that can predict the combined structural, electrical, electrochemical, and thermal response to abuse conditions.  If such simulation tools are integrated into the product development process, the resultant data has the potential to inform decisions during development and create highly optimized designs.

Academic and national laboratory researchers have pioneered these models1-3, but there is currently no consensus on the required methods for multi-physics coupling or acceptable degree of homogenization.  If coupling is present between the mechanical and electrical or thermal solvers, it is typically one-way and largely manually applied, which requires highly advanced users to implement due to mesh and element compatibility issues.

In order to initiate a much larger investigation into the abuse response of Li-ion cells, modules, and packs, a coupled structural, electrical, and thermal simulation framework has been developed within the commercially available LS-DYNA software.  The finite element model leverages a three-dimensional mesh structure that fully resolves the unit cell components.  Depending on the time scale of the mechanical crush, coupling with the mechanical solver can be one-way for impact loading conditions that occur in the sub-second time scale, or two-way for continuous crush in the tens to hundreds of seconds time scale.  Measurements of the resistance between unit cell layers as a function of applied pressure are reported and used to parameterize the coupling between the structural, electrical, and thermal solvers.  A spatially distributed equivalent circuit model predicts the electrical response with minimal computational complexity.  The thermal model provides information to schedule the electrical model parameters, while simultaneously accepting irreversible and reversible sources of heat generation.  The spatially distributed models of the electrical and thermal dynamics allow for the localization of current density and corresponding temperature response to provide the necessary tool structure for predicting the onset of thermal runaway.

Future work will focus on the structural material models and failure conditions required to quantitatively predict the battery crush response to a variety of loading conditions.  Plans for additional multi-physics functionality within the simulation tool will also be highlighted.

References:

E. Sahraei, R. Hill, and T. Wierzbicki, J. Power Sources, 201, 307 – 321 (2012).

E. Sahraei, M. Kahn, J. Meier, and T. Wierzbicki, RSC Adv., 5, 80369 – 80380 (2015).

C. Zhang, S. Santhanagopalan, M. A. Sprague, and A. A. Pesaran, J. Power Sources, 290, 102 – 113 (2015).
Electrical Current Oscillations in Lower-Dimensional Battery Electrodes
Authors: Yamada Hidenori , Bandaru Prabhakar R
Published: February 2020

In order to enhance the capacity of a charge storage device, nanostructures such as one-dimensional (1-D) carbon nanotubes (CNTs) have often been employed, much of the time with the effect of increasing the surface area exposed to electrolyte or enhancing the electrode inter-connections and reducing the electrical resistance.  Previous work also demonstrated the need for new physics based on lower dimensional density of states (DoS), as would occur in CNTs or graphene [1].  Here, for nanostructured battery electrodes, we propose a new current-voltage (I-V) model based on 2D and 1D DoS, and compare with related experiments. The model is broadly based on Marcus-Hush-Chidsey (MHC) kinetics and is aimed to extend the utility of the MHC formulations, to a larger class of materials and situations. We employ an integral expression for current, which involves the DoS, the Fermi-Dirac function, and the Arrhenius rate law as the basis.  Our model provides better agreement to measured chronopotentiometry data on Li-ion batteries with nanostructured organic polymer electrodes, compared to previous analysis.  An interesting feature of our model is the prediction in one-dimensional nanostructures of electrical current oscillations in the I-V curve, corresponding to the gradual population (and de-population) of each successive sub-band, provided that the sub-band widths are comparable to the reorganization energy. We posit that the consideration of a variable/non-constant DOS in MHC electrokinetics may yield tests of dimensional character and concomitant contribution to electrochemical systems.

[1] H. Yamada and P. R. Bandaru, Appl. Phys. Lett. 102, 173113 (2013), ibid 104, 213901 (2014).
Point-of-Care Screening Tools for Cancer
Authors: Stefan-van Staden Raluca-Ioana
Published: February 2020

New nanostructured nanomaterials were proposed for the design of stochastic sensors used for the assay of different tumor biomarkers. The new designed stochastic sensors were very sensitive, and present low determination limits, which made possible early detection of cancer in asymptomatic patients. The advantages of using of such tools for screening of biological fluids were: fast screening - the results being available within minutes; no sample preparation required - the biological fluid being used as taken from patients; very high sensitivities and low determination limits; low cost of screening test compared with ELISA method; high reliability for both qualitative and quantitative assay of cancer biomarkers; early detection of cancers was possible due to the very low limit of determination of the stochastic sensors.. The reliability of such microsensors allowed them to be used as point-of-care tools.
Fabrication and In Vivo Evaluation of Low-Invasive Patch Type Glucose Sensors
Authors: Yasuzawa Mikito , Li Jiang , Fuchiwaki Yusuke
Published: February 2020

Continuous glucose monitoring system (CGMS) using implantable glucose sensor have provided significant benefit on the management of diabetic health care, since it can present not only the point of glucose degree but also its trend. Although the present glucose degree is same, rising and lowering phenomenon of blood glucose lead to an opposite treatment action. In addition, daily trend observation is useful for the evaluation and improvement of individual pharmacotherapy.  However, since sensor device of CGM at a present day requires a length of 1 cm to be inserted in skin, development of a lower-invasive CGMS is expected for the improvement of diabetic patients’ quality of life.

    In this study, a fine tapered needle shape glucose sensor, which has sensing region at the tip of a fine tapered electrode, was proposed.  Since the sensing region is at the tip of tapered electrode, it only requires the sensor tip to be implanted in the tissue for glucose monitoring. In other words, it can be possible to perform as a patch type sensor, which impresses the user as a sticking sensor instead of a implanting sensor.  Fine platinum-iridium alloy wire with a diameter of 0.17 mm was placed inside the tapered PEEK tube and glucose oxidase (GOx) was immobilized on the surface of platinum electrode by using the combination of electrodeposition and electropolymerization technique. Ag/AgCl film was prepared on the outer surface of PEEK tube in order to be employed as reference electrode together as counter electrode.  Glucose sensor properties of the obtained GOx-immobilized electrode were evaluated by using in vitro and in vivo measurements. A patch type sensor with insert length of 1 mm was implanted in a rabbit. Clear sensor response corresponding to glucose concentration change was confirmed.

Figure 1