bluuebunny/crossref_metadata_2025 huggingface dataset:
Fighting the Noise: Towards the Limits of Subsecond X-ray Tomographic Microscopy of PEFC
Authors: Xu Hong , Bührer Minna , Marone Federica , Schmidt Thomas J. , Büchi Felix N , Eller Jens
Published: February 2020

Management and removal of liquid water is essential to maintain and improve the overall performance of polymer electrolyte fuel cells (PEFC). X-ray tomographic microscopy (XTM) of PEFCs has been proven as a valuable tool in order to understand accumulation of liquid water in the gas diffusion layer (GDL), both with in-situ [1-3] and operando setups [4-8]. Progress in operando XTM of PEFCs has paved the way for 4D imaging studies of the water distribution in the GDL [9]. In order to capture the water dynamics at high current density operation a further decrease of the scan time towards 0.1 s is aspired and the consequences of the reduced signal to noise ratio in the XTM data on water detectability need to be quantified.

In this work different imaging parameters and their consequences on the contrast-to-noise ratio (CNR) of water versus void have been studied with an ex-situ XTM experiment at the TOMCAT beamline of the Swiss Light Source (SLS) at Paul Scherrer Institut (PSI). The cathode channels of a double channel XTM cell [8] have been filled with liquid water, while keeping the anode channels empty, as shown in Figure 1. The CNR(H2O/Void) in the gas channels serves as an indicator for contrast between liquid water and void in the GDL to derive optimized imaging parameters for operando conditions. Over a range of monochromatic beam energies (13.5 – 21 keV) and scan times (0.2 – 10 s) a beam energy of 13.5 keV was found to be mostly appropriate as it provides the highest CNR value. The presentation will focus on the consequences of sub-second XTM acquisition time on the image processing pipeline for the detectability of small water droplets and their connecting paths.

References

[1] R. Flückiger, F. Marone, M. Stampanoni, A. Wokaun, F. N. Büchi., Electrochim. Acta, 56, 2254-2262, 2011.

[2] A. Lamibrac, J. Roth, M. Toulec, F. Marone, M. Stampanoni, F. N. Büchi, J. Electrochem. Soc., 163, F202-F209, 2016.

[3] I. V. Zenyuk, D.Y. Parkinson, G. Hwang, A.Z. Weber,, Electrochem. Comm., 53, 24-28, 2015.

[4] A. Schneider, C. Wieser, J. Roth, L. Helfen, J. Power Sources, 195, 6349-6355, 2010.

[5] P. Krüger, H. Markötter, J. Haussmann, M. Klages, T. Arlt, J. Banhart, Ch. Hartnig, I. Manke, J. Scholta, J. Power Sources, 196, 5250-5255, 2011.

[6] J. Eller T. Rosén, F. Marone, M. Stampanoni, A. Wokaun, F. N. Büchi, J. Electrochem. Soc., 158, B963-B970

2011.

[7] T. Rosén, J. Eller, J. Kang, N. I. Prasianakis, J. Mantzaras, F. N. Büchi, J. Electrochem. Soc., 159, F536-F544 2012.

[8] J. Eller, J. Roth, F. Marone, M. Stampanoni, F. N. Büchi, J. Electrochem. Soc., 164, F115-F126, 2017.

[9] J. Eller, F. Marone, F. N. Büchi, ECS Trans., 69, 523-531, 2015.

Figure 1: Quantitative comparison of the contrast-to-noise ratio (CNR) between water and void for different beam energies and scan times (middle); qualitative through-plane slices are given for 0.5 s (left) and 10 s scan time (right).

Figure 1
Investigation of Hydrogen Starvation of Polymer Electrolyte Fuel Cells in Freezing Condition Using Reference Electrode
Authors: Hu Leiming , Hong Bo Ki , Oh Jong-Gil , Litster Shawn
Published: February 2020

For vehicles using polymer electrolyte fuel cells (PEFCs) to be commercially competitive with conventional internal combustion engine vehicles, three major challenges must be resolved, i.e., cost, performance and durability (1). The durability of a PEFC system can be largely affected by hydrogen starvation. During the startup/shut down process (2) of the fuel cell system, or when the flow channel is blocked by water or ice, local hydrogen starvation arises within one or many of the cells in the fuel cell stack. When this happens, hydrogen oxidation reaction (HOR) on the anode side cannot support the current imposed by the other cells. In that case, the anode half-cell potential increases relative to the cathode potential, and the cell voltage reverses. The high anode half-cell potential during cell reversal leads to water electrolysis and carbon corrosion reaction, the latter of which causes damage to the carbon support in the catalyst layer and leads to severe cell performance degradation. Hydrogen starvation in normal operating condition has been extensively investigated (3-5). However, little research has been conducted on cell reversal at sub-zero temperatures.

In past work on studying cell reversal, the anode potential and the corresponding reactions are estimated from the fuel cell voltage assuming a stable cathode potential. However, at sub-zero temperatures, ice formation affects both the anode and cathode potentials, which makes it difficult to evaluate the cell reversal origin and the anode half-cell potential. To better understand hydrogen starvation and cell reversal behavior of PEFCs sub-zero temperatures, a specially designed, easy-handling reference electrode has been developed and integrated with the membrane electrode assembly (MEA) in order to separate anode and cathode potentials, as shown in Fig. 1. The external hydrogen reference electrode is attached to the MEA through a thin polymer electrolyte bridge. With the reference electrode installed, the cell reversal behavior is investigated for both the typical operating temperatures (65-80 oC) and the sub-zero temperatures (e.g., -15 oC). At 65 oC, the cell voltage change during hydrogen starvation is mainly affected by anode potential change, which shows the potential plateau for water electrolysis and carbon corrosion. In contrast, the cell voltage experiences several transient states at -15 oC. Using the reference electrode, we identify that only one of the potential plateaus in caused by changes in the anode potential and the remainder are a result of phenomena related to ice formation in the cathode. Herein, we present several unique aspects related to hydrogen starvation cell reversal at sub-zero temperatures that are identified using the reference electrode.

Figure 1
Strategies to Improve PFSA Membrane Durability: Benefits and Challenges
Authors: Zaton Marta , Donzel Nicolas , Pasquini Luca , Cavaliere Sara , Rozière Jacques , Jones Deborah J.
Published: February 2020

The durability of ionomer membranes is an important factor affecting the lifetime of proton exchange membrane fuel cells. Degradation of ionomer membrane causes performance losses that accelerate with time and result in catastrophic MEA failure. Membrane instability has two main origins mechanical fatigue and chemical degradation. Both modes strongly depend on the operating conditions applied: temperature, relative humidity, humidity cycling, reactant pressure, applied voltage and properties of the membrane, mainly the ionomer type and equivalent weight (EW), and membrane thickness. Thin membranes (<<20 µm) with low equivalent weight (<<800 EW) are required to achieve industry targets for FCEV however they are also more prone to undergo accelerated degradation.

This work focuses on the development and evaluation of different methods to increase durability through the development of a highly heterogeneous membrane system comprising a reinforcing component, radical scavenger and/or hydrogen peroxide decomposition catalyst and in which the architecture of the membrane is designed at the nano- to micro-metric length scales, the latter facilitated by the use of solution casting processes. Electrospun nanofibres provide mechanical strength, ensure low membrane swelling when exposed to humidity cycles, and also provide an appropriate distribution medium for radical scavenging species. This presentation will discuss benefits and remaining challenges associated with efficiency and stability of mechanical and chemical reinforcements.

Acknowledgement: This project has received funding from the Fuel Cells and Hydrogen 2 Joint Undertaking under grant agreement No 671465 VOLUMETRIQ. This Joint Undertaking receives support from the European Union’s Horizon 2020 research and innovation programme.
New Modified Nitrogen-Doped Graphene (N-G)/Metal Organic Framework (MOF) Derived Microporous Catalyst for Oxygen Reduction Reaction (ORR)
Authors: Zhuang Shiqiang , Nunna Bharathbabu , Lee Eon Soo
Published: February 2020

Nitrogen-doped graphene (N-G), which is one of non-platinum group metal (non-PGM) catalysts, has a huge potential in many electrochemical systems such as fuel cells due to the high raw material cost of PGM catalyst. However, there is a significant gap between the current level of electrochemical performance of N-G catalysts and that of PGM catalysts. A new approach, which is modifying the N-G catalyst by metal-organic framework materials (MOFs) with nanoscale high energy wet ball milling method, is investigated to enhance the electrochemical performance of N-G catalysts. The physical and chemical properties of new synthesized N-G/MOF catalysts are characterized several characterization methods such as XPS, XAS, SEM-EDS, TEM, XRD, BET and RRDE. The processing control of the synthesis process is studied by characterizing a series of N-G/MOF catalysts synthesized with different grinding speed and grinding time. The successful accomplishment of the new N-G/MOF catalysts will provide the substantial way to the cost-effective and fuel-efficient energy conversion system.
Titanium Oxide-Supported Electrocatalysts for Polymer Electrolyte Fuel Cells
Authors: Ioroi Tsutomu
Published: February 2020

Durability of the catalyst materials is one of the issue hindering widespread commercialization of fuel cell vehicles because durability is the problem not only for the product life, but also for product cost. Carbon corrosion of the electrode materials such as catalyst support and MPL is one of the causes of performance fading, so that much more stable catalyst support material is indispensable to improve the durability [1]. So far we have developed Magneli-phase titanium oxide supported Pt catalysts as corrosion-resistant PEFC electrocatalysts at higher potentials, however catalyst activity was unsatisfactory [2]. To improve ORR activity of Pt/Ti4O7 catalysts further, alloying Pt with transition metal such as Ni and Co is effective and commonly used way for carbon-supported catalysts. In this work, we report Pt-Ni or Co alloy catalysts deposited on the corrosion-resistant Ti4O7 supports. Sub-stoichiometric titanium oxide was prepared by pulsed UV laser technique [2], and Pt-alloy catalyst particles were prepared by conventional impregnation/reduction method. From SEM and XRD results, it was found that deposited alloy particles were ordered Pt3Ni/Pt3Co phase with particle diameter of 5-20 nm. Half-cell study revealed that Pt3Ni/Ti4O7 shows increased ORR activity (0.80 mA cm-2
Pt @0.9 V in 0.1 M HClO4, 25oC) compared to commercial Pt/C catalyst (TKK TEC10V40E, 0.36 mA cm-2
Pt). MEA with Pt3Ni/Ti4O7 cathode was also examined, and confirmed the improved ORR activity. To examine the stability against higher potentials under MEA condition, accelerated stress test (AST) for start-up/shut-down was conducted according to FCCJ protocol. Similar to the Pt/Ti4O7 catalysts [2], improved stability of Ti4O7-supported Pt3Ni was also demonstrated. Detailed physicochemical properties of the prepared catalyst and stability of the cell performance will be discussed at the meeting.

Reference

1) T. Arai, T. Ozaki, K. Amemiya, T. Takahashi, SAE International Journal of Alternative Powertrains, Vol. 6(1), (2017).

2) T. Ioroi, T. Akita, M. Asahi, Y. Yamazaki, Z. Siroma, N. Fujiwara, K. Yasuda, J. Power Sources, 223, 183 (2013).
Bi-Functional Electrodes for Zinc-Air Batteries
Authors: Xu Nengneng , Qiao Jinli , Wang Yudong , Zhou Xiao-Dong
Published: February 2020

(La,Ca)MnO3 has been proposed as a candidate for the air electrode in a zinc-air battery, however it goes through a decomposition reaction in the presence of 6 KOH during cycling. In this work, we report the electrochemical properties of a nanocomposite, consisting of CaO nanoparticles, La2O3 nanorods, and MnO2 nanotubes, supported on carbon nanotubes (CNTs). This nanocomposite exhibits a superior bi-functional activity towards oxygen reduction reaction and oxygen evolution reaction in a zinc-air battery with a discharge peak power density of ~203 mW cm-2, a current density of ~150 mA cm-2 at 1.0 V cell voltage, and an energy density of ~725 mAh g-1., all of which are better than these of commercial Pt/C and IrO2/C. a long life test for power generation is demonstrated by replacing a total of 30th pieces of Zn plates and electrolyte. Furthermore, this rechargeable ZAB exhibits a small charge–discharge voltage polarization (~0.77 V) and excellent stability (534 cycles) cycling at 10 mA cm-2.
(Invited) Mapping Internal Polarization in YSZ Electrolytes Using Grain Size
Authors: Chen I-Wei , Dong Yanhao
Published: February 2020

Polarization development near the electrodes is important for the performance of YSZ devices. However, there are very difficult to measure experimentally. Embedded electrodes have been used to obtain a few readings across the electrolyte thickness, but so far there has been no report that provides a continuous mapping of the electrolyte polarization. Here we demonstrate that grain growth provides a means for such mapping. The method is based on the observation that cation mobility in YSZ (as well as other fluorite structured oxides) increases rapidly with decreasing oxygen potential.

Placing YSZ under a large current in various atmospheres between electrodes of various configurations, we have created many grain size distributions that vary continuously or discontinuously between the cathode and anode. Aided by the correlation between grain boundary mobility and non-stoichiometry, the grain size map can be converted to a polarization map. Such mapping allows us to quantitatively assess the influence of electrode kinetics and atmosphere on internal polarization under large current conditions.

Under the same conditions of enhanced grain growth, we have observed widespread cavitation throughout YSZ in nearly all the samples tested in a reducing atmosphere. This is surprising since the prevailing theory attributes cavitation to oxygen bubbles, and it predicts oxygen bubbles to form inside the YSZ electrolyte only under a large positive oxygen potential. Yet the large grain size in our cavitated samples clearly indicates a large negative oxygen potential. Therefore, we must rule out the oxygen bubble model. Instead, we propose that cavitation in these samples is in the form of voids, which come from condensation of supersaturated oxygen vacancies.

These results further suggest strong electronic conduction in the electrolyte. Indeed, the observation of cavitation implies internal reactions between electronic defects and ionic defects, rendering the latter no longer fully ionized. These reactions have the effect of buffering the oxygen potential inside the electrolyte. The observed oxygen potential and grain size transition can only be successfully modeled by taking into account such internal reactions.
Strain-Based Scanning Probe Techniques for Imaging Space Charge Regions in Sm-Doped Ceria
Authors: Gerwe Brian S , Adler Stuart B. , Esfahani Ehsan N , Wang Peiqi , Chen Qian Nataly , Li Jiangyu
Published: February 2020

Widespread implementation of renewable, but intermittent, energy sources is contingent upon a new generation of high performance batteries and electrolysis devices to store and convert energy chemically. However, development efforts are hindered by limited knowledge of kinetic and transport properties at the nanoscale, which often differ substantially from bulk properties. A deeper understanding of localized properties and their impact on material and device performance would facilitate further advancements in electrode materials which could lead to more cost effective energy storage and conversion devices.

Traditional characterization techniques, such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), can probe kinetic and transport rates as functions of applied potential and timescale, but cannot resolve spatial variations. To elucidate localized response under dynamic polarization, we are currently developing scanning probe techniques that will act as a nanoscale witness of local response in operando during EIS measurements. These techniques include electrochemical strain microscopy (ESM) and, more recently, scanning thermionic microscopy (STIM). In ESM a potential is applied to a conductive atomic force microscopy (AFM) tip, thus generating an electric field in a sample to drive ionic motion. This causes a strain in the material, often interpreted as Vegard strain, which is detected as a deflection of the AFM tip1. STIM functions by applying a periodic temperature perturbation from a heating element located on top of the AFM tip, inducing ionic motion by thermal stress. Again, material strain is detected by deflection of the tip, from which the fourth harmonic of the input frequency is related to shifts in chemical composition2.

We are currently applying these methods to two model systems: Gd-doped CeO2 , a common solid oxide fuel cell electrolyte, and Li1-xCoO2 ,often used as a positive electrode material in solid state lithium-ion batteries.

References:

1. Balke, N. et al. Nanoscale mapping of ion diffusion in a lithium-ion battery cathode. Nat. Nanotechnol.
5,749–754 (2010).

2. Eshghinejad, A. et al. Scanning thermo-ionic microscopy for probing local electrochemistry at the nanoscale. J. Appl. Phys.
119, 205110 (2016).
Bis(2-chloroethyl) ether-1,3-bis[3-(Dimethylamino)propyl]urea copolymer -Chitosan–Poly(acrylamide-co-diallyldimethylammonium chloride) blends as membranes For Alkaline Anion-exchange Membranes
Authors: Ao Bei , Wei Ya Nan , Qiao Jin Li
Published: February 2020

Solid, thin, and flexible energy storage devices are required to power flexible and wearable technologies which are rapidly growing in importance. One of the key components for solid-state energy storage is a polymer electrolyte which eliminates liquid electrolyte leakage and minimizes bulky packaging. An ideal polymer electrolyte for supercapacitors should exhibit the following properties: (a) high ionic conductivity; (b) a wide electrochemical stability window for maximum cell voltage; and (c) high environmental and temperature stability for device safety and long service life[1-3].

In this paper, the novel, low-cost alkaline anion-exchange membranes (CS/PDDA), made from Chitosan and poly(diallyldimethylammonium chloride) blends, are successfully synthesized by a combined thermal and chemical cross-linking technique. The hydroxide conductivity (OH-), water uptake, ion exchange capacity (IEC), thermal stability, oxidative stability and alkaline stability of CS/PDDA membranes are measured to evaluate their applicability in electrochemical capacitors. The effects of membrane composition on OH- conductivity are studied using AC impedance technique. It is found that by cross-linking modifications, the membranes exhibit high OH- conductivity of 0.0162S cm-1 is achieved at m (CS) : m (PDDA)=1:0.5. The CS/PDDA membranes as electrode materials for supercapacitor demonstrated a wide voltage window (1.5 V), and exhibit high specific capacitance of 27.6 mF cm-2 at 100 mV s-1.

References

[1] H. Gao, K. Lian, RSC Advances, 4,33091(2014) .

[2] H. Gao, J. Li, K. Lian, RSC Advances, 4,21332(2014).

[3] M. Kaempgen, C.K. Chan, J. Ma, Y. Cui, G. Gruner, Nano Letters, 9,1872(2009).
A Novel Pr2NiO4/Pr6O11 Based Composite As the Cathode for Solid Oxide Fuel Cells
Authors: Wang Yudong , Dogdibegovic Emir , Zhou Xiao-Dong
Published: February 2020

Praseodymium nickelate (Pr2NiO4) is an active oxygen electrode in solid oxide fuel cells, however it undergoes a phase transition at elevated temperatures or under an electrochemical operation to form PrOx and higher ordered nickelate phase. In this work, we attempt to suppress the phase transition by adding Pr6O11 to Pr2NiO4 to form a composite. Two approaches are adopted: the first is to infiltrate Pr2NiO4 with Pr6O11 and the second one is to use a mixture of Pr2NiO4 and Pr6O11 powders. In case or (Pr,Nd)2NiO4 is used, the 2nd oxide phase is subsequently changed to (Pr,Nd)2O3. Anode supported single cells are used to measure the performance of the composite electrode. XRD is used to analyze the cathode structure and does show the suppression on phase evolution. In addition, the infiltrated cells show a high initial performance and the performance is stable during the 100-hours accelerated measurement.
Solid Acid Proton Conductors: Insights into Proton Conduction Mechanisms and Advances in Electrode Architectures
Authors: Elgammal Ramez Ahmed , Zawodzinski Thomas A.
Published: February 2020

Intermediate-temperature fuel cell (ITFC) systems have recently received significant interest for stationary distributed generation applications. As opposed to high-temperature (> 650 °C) solid-oxide fuel cells (SOFCs), intermediate-temperature systems (200-500 °C) may be capable of reaching cost targets by relaxing material re­quirements for interconnects and systems-level requirements for insulation, heat exchangers, and other balance-of-plant elements. ITFCs may operate on minimally-processed fossil fuels such as natural gas, rather than the ultra-purified hydrogen required for low-temperature (< 100 °C) polymer electrolyte membrane fuel cells (PEMFCs), a feature that could possibly accelerate adoption due to the existence of established distribution networks for these fuels.

Various proton conducting solid acids of the general formula MHxXO4 (M = K, Cs, Nd; x = 0-2; X = S, P) have attracted considerable interest as electrolytes for ITFCs. We will present an overview of distinguishing structural features of these solid acids, temperature induced phase transitions, and comment on the varying mechanisms of proton conduction using studies from NMR, XRD, FT-IR, Raman microscopy, and AC impedance spectroscopy.

The most promising candidate for solid acid fuel cells (SAFCs) is CsH2PO4 (CDP). The current state-of-the-art SAFC utilizes thin films of platinum nanoparticles on a porous framework of CDP electrolyte. Our methodology to improve Pt utilization, increase electrode surface area, and electrical interconnectivity was achieved by using carbon-based supports for the electrocatalyst and homogenizing framework with CDP. Using a combination of chemical functionalization of nanostructured carbon and infiltration of CDP, we fabricated nanocomposite electrodes that demonstrated vastly superior performance. For example, at 0.8V and 250 °C, a hydrogen-air SAFC using this new electrode architecture we found an improvement in power density by almost a factor of 2, with a decrease in Pt loading of a factor of 15. Furthermore, with Pt loadings of 0.18 mgPt cm-2 we observed peak power densities of in excess of 300 mW cm-2. We will present a detailed account of these effects, comment on improved stability and durability of these electrodes, and illustrate using a combination of SEM and TEM that nanoconfined CDP exists within the electrode. Finally, we will discuss future directions including advanced manufacturing enabled by the nanocomposite structure.

Acknowledgements

This work is supported by ARPA-E under Cooperative Agreement Number DE-AR0000499.
Thermodynamics and Kinetics of Alkali Insertion in VOPO4 Polymorphs
Authors: Lin Yuh-Chieh , Hidalgo Marc Francis , Chu Iek-Heng , Chernova Natasha , Whittingham M. Stanley , Ong Shyue Ping
Published: February 2020

Multi-electron polyanion cathodes offer the potential for achieving both high voltage and high capacity in rechargeable alkali-ion batteries. Among the few materials known to exhibit multi-electron cycling, the polymorphs of VOPO4 , which operate on the V3+«V4+«V5+ redox couples, are particularly promising due to the high gravimetric capacities that have been achieved and the high voltage of the V4+/
5+ couple. In this talk, we will provide an integrated computational and experimental study of the thermodynamics and kinetics of alkali (Li/Na) insertion into the α-I, β and ε polymorphs of VOPO4. We show that differences in voltage and rate capability of these different polymorphs for Li and Na insertion can be traced back to their fundamentally different VO6-PO4 frameworks. We will also provide an overview of the different contributions to the thermodynamic stability of the different polymorphs. This work was supported as part of the NorthEast Center for Chemical Energy Storage (NECCES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0012583.
Analysis of Charge / Discharge Behavior Using Simple and High-Precision Capacity Measurement: Application to Commercially Available Large-Format Lithium-Ion Batteries
Authors: Yamazaki Atsuko , Kobayashi Yo , Mita Yuichi , Miyashiro Hajime
Published: February 2020

Lithium-ion batteries are adopted as stationary applications because of their high voltage, high-energy density and high efficiency properties. The batteries for stationary use are expected for long-term operation more than 20 years with 80 % capacity retention. Therefore suitable estimation of the operation period of the lithium-ion batteries are required. High-precision charge / discharge measurement is proposed to estimate an effective life time within short test periods [1]. Then, we developed a simple and high-precision charge / discharge capacity measurement system for large-format cells and determined the capacity fade of 20Ah class battery (SCiBTM by TOSHIBA Corp.). Cells were charged and discharged at 10A(C/2) constant current between 2.7 and 1.5 V at 45(±0.3) °C. The sampling rate of current and voltage during charge / discharge was 100 ms to minimize the counting error of integrated capacity. Figure 1 shows the capacity trends with cycle operation at above condition. The capacity decreased linearly with cycles within the measurement period. The capacity loss per cycle was estimated as 3.4 mAh/cyc by averaging 35 cycles according to the linear approximation as shown in Fig.1. The coulombic loss per cycle was about 8.1 mAh/cyc which was defined as the difference between charge and discharge capacity. This value was more than two times as large as the capacity loss per cycle. The difference between them is probably due to internal reaction without direct involvement of capacity loss during operation. This result suggested that chemical self-discharge process such as shuttle mechanism may be a dominant factor of the estimated coulombic loss.

[1] A. J. Smith, J.C. Burns, S. Trussler, and J. R. Dahn, J. Electrochem. Soc.,
157, A196-A202 (2010).

Figure 1
Understanding Morphology Evolution in Lithium Electrodeposition
Authors: Tewari Deepti , Liu Zhixiao , Mukherjee Partha P.
Published: February 2020

Lithium-ion batteries are poised to play an important role in the push for electric vehicles. Electroplating and possible dendritic growth, however, have been a safety concern. Non-uniform electrodeposition and subsequent growth may cause short circuit. Apart from catastrophic failure, Li plating results in the battery performance decay as well. There is a need for a better understanding of the factors that are most critical in the nucleation and growth of Li electrodeposition and the morphology evolution thereof. The metal ion reaches the electrode surface where it is reduced. The metal atom can thereafter diffuse inside the bulk electrode or aggregate on the surface under some specific set of conditions and form a variety of structures on the electrode surface, like small islands, uniform film, mossy or filament like structure or dendrite (as schematically shown in Figure 1). Physicochemical determinants affecting electrodeposition include the adsorption energy of metal atom on electrode surface, diffusion barrier for metal atom in the bulk electrode compared to that on the electrode surface, the crystallographic nature of the electrode surface, the strength of cohesive metal-metal interaction. Beyond the nature of the electrode material, the operating temperature, current density and applied potential can also affect the electrodeposition rate, which consequently control the morphology evolution. In this study, a mesoscale interfacial modeling and analysis is presented in order to investigate the lithium electrodeposition regimes and morphology evolution.

Figure 1
Solid-Electrolyte Interphase Reinforcement Strategy through Introducing Covalently Anchored Multi-Functional Components for Li-Alloy Anodes
Authors: Gao Yue , Wang Donghai
Published: February 2020

Li-alloy based anode materials are very promising for breaking current energy limits of lithium-ion battery technologies. At present, their practical applications are mainly hindered by the solid-electrolyte interphase (SEI) stability issue. SEIs of Li-alloy anode materials exhibit insufficient surface passivation to prevent electrolyte penetration and suffer from cracking and peeling-off issues due to their poor tolerance to volume changes, consuming additional electrolyte and material for SEI repair.

Here we propose a chemical SEI reinforcement strategy via introducing multiple functional components as SEI components, which have strong interactions with Li-alloy material surface and effectively improve the SEI stability, including its tolerance to volume changes and surface passivation during cycling. Using a modular synthetic approach, we realized a one-step fabrication of diverse components with designed structure and anchoring amount, allowing the facile construction and optimization of the SEI. Si nanoparticle (SiNP) materials were used as the platform for demonstrating this concept. After screening and optimizing the SEI structure using various pre-anchored components, one chemically reinforced SEI (CR-SEI), reinforced by a combination of two functional components with moderate anchoring amount shows significantly improved stability compared to the SEI derived from electrolyte with FEC additives. During cycling, the CR-SEI presents unique and stable chemical composition, resulted form the addtion of pre-designed functional components, which differs from the composition of conventioal SEI. Meanwhile, the CR-SEI also maintains good and durable morphology during cycling. After many cycles, only very limited “SEI accumulation” was observed in the TEM images of SiNP with CR-SEI and the CR-SEI remains thin and uniform. This is in contrast with the poor stability of conventional SEI. Large amount of SEI accumulation and SiNPs decrease in size were observed. Finally, owing to the improved SEI stability, SiNP electrode with CR-SEI presents significantly increased electrochemical performance, including increased 1st cycle Coulombic efficiency (CE), improved cycling CE and capacity retention, and limited increase in electrochemical impedance. Particularly, the SiNP electrode with CR-SEI present much better cycle life in the full-cell system than one containing electrolyte additive improved SEI. Moreover, this strategy has also been applied to GeNP SEI reinforcement with dramatic enhancement of the SEI stability, suggesting its viability for other Li-alloy materials. Owing to the facility and modularity of the synthetic approach, we are also able to further examine more functional components potentially suitable for SEI reinforcement.
Thermodynamic Investigation of Selected Compositions in the LiNiO2-LiMnO2-LiCoO2 System As Lithium Ion Battery Cathode Materials
Authors: Masoumi Maryam , Cupid Damian Marlon , Seifert Hans Jürgen
Published: February 2020

The choice of cathode material is critical for determining the performance and safety of lithium ion batteries. Therefore, the development and optimization of new chemistries for cathodes of lithium ion cells is of major importance. Layered structured lithium mixed transition metal oxides with the general formula of LiNixMnyCozO2 (x + y + z = 1) and an α-NaFeO2-type layered structure (space group ) are attractive intercalation type cathode materials which overcome the limitations of LiCoO2, the most commonly used cathode for lithium ion batteries in portable applications. These NMC materials not only are isostructural to LiCoO2, but also offer comparatively higher reversible capacity, lower cost, and improved thermal stability, which are important characteristics for large scale applications.

Although the structural characteristics and electrochemical behavior of many promising compositions in the NMC system have been investigated to some extent, there are very few studies devoted to the thermodynamic properties of this class of materials. The enthalpies of formation of LiNi1−xCoxO2 compounds were determined by Wang and Navrotsky [1] using high temperature oxide solution calorimetry and the enthalpy of formation of LiNi1/3Mn1/3Co1/3O2 and its chemically delithiated phases were measured by Idemoto and Matsui [2] using acid solution calorimetry. In the present work, with the aim of investigating the effect of cation substitution on thermodynamic stability of NMC materials, the standard enthalpies of formation of two different series of sol-gel made NMC samples, namely LiNixMnxCo1-2xO2 (0 ≤ x ≤ 0.5) and LiNi0.8-yMnyCo0.2O2 (0 ≤ y ≤ 0.4), are determined by high-temperature oxide-melt drop solution calorimetry. The compositions are selected to include the technologically relevant NMC111, NMC442, NMC532 and NMC622 compounds.

It is shown that LiNixMnyCozO2 with layered structure is a nearly ideal solid solution of LiCoO2, LiNiO2 and LiNi0.5Mn05O2. Our calorimetry results show that the standard enthalpies of formation of the compounds from the elements vary almost linearly with composition in the respective area. Furthermore, based on our experimental heat of formation data and available low temperature heat capacity data for LiCoO2, LiNiO2 and LiNi0.5Mn05O2, a model for the variation of the Gibb’s free energy of formation and equilibrium potentials of the NMCs with composition at room temperature is presented. In addition, key electrochemical tests were performed to establish a relationship between the thermodynamic properties and electrochemical performance of the cathode materials. This work should help clarify the structure–property relationships in these compounds.

M.Wang, & A. Navrotsky, Solid State Ionics 166 (2004), 167-173.

Y.Idemoto & T. Matsui, Solid State Ionics 179 (2008), 625-635.
Designing Redox Polymers for Mediated Bioelectrocatalysis
Authors: Minteer Shelley D.
Published: February 2020

Enzymatic biosensors have been developed for a variety of analytes, including: glucose, lactate, pesticides, nerve agents, peroxide, oxygen, and alcohols. They generally involve immobilization of an oxidoreductase enzyme on an electrode surface. Although direct bioelectrocatalysis between the enzyme and the electrode surface is the preferred mode for enzymatic biosensors, many enzymes are not capable of direct electron transfer. Therefore, mediated bioelectrocatalysis is popular in the enzymatic biosensor field, where an additional redox species is used to relay the electron between the enzyme and the electrode surface. This paper will detail the rational design of linear polyethylenimine-based redox polymers for mediated bioelectrocatalysis, where the redox polymer is used both to immobilize the enzyme and to mediate the electron transfer. This will include polymers where the ferrocene and quinone redox species is optimized for the enzymatic system employed (i.e. glucose oxidase versus glucose dehydrogenase). This paper will discuss the importance of redox potential, redox reversibility, self-exchange rate, interaction with the enzyme, and crosslinking on the properties of the polymer-modified electrodes.
Novel Hierarchically Fabricated Highly Conductive Flexible Electrochemical Biosensor Strips
Authors: Piraman Shakkthivel , Madhuvilakku Rajesh , Alagar Srinivasan , Mariappan Ramalakshmi
Published: February 2020

Abstract

As a growing aspect of materials science, enormous numbers of synthesis routes have been identified to produce nanomaterials, particularly through simple methodologies. For the first time, a flexible self-assembled AuNPs on poly diallyldimethylammonium chloride (PDDA) binded PANI disposable strip sensor is demonstrated in this work. The flexible strip electrodes are prepared by using polyester overhead projector transparent films (OHP), polyaniline (PANI) conducting polymer was deposited on the chemically activated OHP surface. Later, gold nanoparticles (AuNPs) were self-assembled onto the electro-statically binded PDDA-PANI matrix. Owing to the strong electrostatic interaction between the positively charged PDDA molecules and the negatively charged polyaniline play a crucial role in the formation of nanocomposite films. Moreover, the increased the adhesion between the AuNP and the substrate through PDDA anticipated improved stability of the modified electrodes. The structural, morphological and chemical composition of the modified flexible strips were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Transmission electron microscopy (TEM), X-ray photoelectron microcopy (XPS) and Fourier Transform Infra-red Spectroscopy (FT-IR) techniques . Cyclic voltammetric, alternating-current impedance, and amperometric methods were used to investigate the catalytic properties of the assembled sensor strips. The newly fabricated AuNPs/ PDDA/PANI/OHP hierarchical nanostructures are produce favorable microenvironment for electron transfer. The higher electrocatalytic performance characteristics were observed for the AuNPs/ PDDA/PANI/OHP modified electrodes, which are attributed to the synergistic effects of the conducting polymer acting as an electron facilitator and the nanostructured Au film act as catalytic surface. These disposable, flexible and low-cost sensors strips offered alternative for electrode materials for electrochemical biosensor.
Biofilm Formation Behaviors on Graphene By E. coli and S. epidermidis
Authors: Kanematsu Hideyuki , Hirai Nobumitsu , Ogawa Akiko , Kogo Takeshi , Kuroda Daisuke , Utsumi Yuichi , Yamaguchi Akinobu , Ikegai Hajime , Mizunoe Yoshimitsu
Published: February 2020

Biomaterials should have some required performances such as mechanical properties and biocompatibility. From the viewpoint, they have been investigated so far. However, an important factor has been missing in some cases. That is the infection resistance. And the final one is related closely to the biofilm and its control. In this experiment, we focus on graphene, an advanced material. The graphene has many high performances and biocompatibility. From the viewpoint, it may get a chance to be applied to biomaterials. However, our prelimnary experiments showed that graphene has its high sensitivity to resident microbiota and tended to form biofilms easily. Since resident microbiota form complicated flora composed of plural bacteria, it is very hard to tell which bacterium formed biofilm mainly. However, it would be very important to investigate the biofilm formation capability by a certain bacterium, when we come to think about the applicability to biomaterials. In this experiment, we chose E.coli as gram negative bacterium and S.epdermidis as gram positive one, since both cause infections and chronic diseases in our human bodies very often. Graphene was prepared by CVD (Cemical Vapor Deposition) and mechanical methods (tape-detachment process). The specimens were measured and the formation of graphene was confirmed by a Laser Raman Spectroscopy. The specimen was set in spme kinds of laboratory biofilm reactors (LBRs) which we have developed in our loboratory. LBRs were filled with liquid cultures including target bacteira. The test continued in a couple of days at a certain temperature (25 degrees Celsius for E.coli and 37 degrees Celsius for S.epidermidis.) After the immersion test in those LBRs, biofilms on graphene samples were observed and measured by Raman Spectroscopy, staing by crystal violets and optical microscopic observations. The results were compared, analyzed in various cases and the applicability of the advanced material to biomaterials and human bodies was discussed.
(Keynote) Transition Metal Sulfides As Intercalation Cathode Materials for Rechargeable Aluminum Batteries
Authors: Geng Linxiao , Guo Juchen
Published: February 2020

Rechargeable aluminum (Al) batteries are promising technologies for large scale energy storage applications. One of the main challenges hindering the development of rechargeable aluminum batteries is the lacking of understanding of cathode materials. In this study, we investigate a number of transition metal sulfides as the intercalation-type cathode materials for rechargeable Al batteries. Our selection of metal sulfides instead of oxides as Al-ion cathode materials is crucial: Due to the strong coulombic effect, the energy barrier for multivalent ion transport in the oxide crystal structure is very high. Thus, a more polarizable (softer) anionic framework is needed for facile Al-ion intercalation-extraction. The sulfide anion is more polarizable than the oxide anion due to the larger size, making transition metal sulfides promising candidates as Al-ion cathode materials. We hereby demonstrate Chevrel phase molybdenum sulfide (Mo6S8) as the intercalation-type cathode material with aluminum chloride/1-butyl-3-methyimidazolium chloride (AlCl3-[BmIm]Cl) ionic liquid as the electrolyte. Electrochemical characterizations including cyclic voltammetry and galvanostatic charge-discharge demonstrate unambiguous Al intercalation-extraction in the Mo6S8. The X-ray diffraction analysis further indicates the crystal structure change of Mo6S8 after Al intercalation. In addition, we report the synthesis and electrochemical properties of layered TiS2 and cubic Ti2S4 as intercalation-type cathode materials for rechargeable aluminum battery at both room temperature and 50 °C. We further confirmed the aluminum intercalation in the TiS2 and Ti2S4 crystal structure using combined electrochemical analysis and ex-situ XRD. The proposed titanium sulfide cathode materials showed decent reversible capacity and a higher working potential than Mo6S8. Furthermore, our study suggests the low Al ion diffusivity in the titanium sulfide framework induced by strong coulombic intercalation is the key obstacle for fast discharge-charge. This finding could provide guideline for design and synthesis of future titanium sulfides electrode materials.
Rapid Detection of Toxic Heavy Metals with Boron-Doped Diamond Sensors
Authors: Rusinek Cory Allen , Becker Michael F , Ensch Mary , Rechenberg Robert , Hardy Aaron , Wehring Bettina , Schuelke Thomas
Published: February 2020

Toxic heavy metals such as lead (Pb), cadmium (Cd), and mercury (Hg) cause serious health complications and ingestion of these toxins through contaminated drinking water, even at trace levels, has become a prominent issue. Chronic exposure to toxic metals such as Pb, Cd, and Hg is carcinogenic while causing other problems like kidney failure, severe neurotoxicity, and IQ loss. These problems are only magnified in children as several stages of bodily development can be severely hindered. Electroanalytical methods are an attractive technique for trace detection of heavy metals due to low cost of experimental tools, low limits of detection, multi-element analysis capability, and the possibility to package them into sensing devices. Specifically, boron-doped diamond (BDD) is a rugged, yet sensitive electrode material with significant potential in electrochemical sensing. Using square-wave stripping voltammetry (SWSV), we have developed BDD micro-electrode arrays (MEAs) as well as macro-electrode disks, achieving detection limits as low as 200 parts-per-trillion (ppt) for Pb with a deposition time of just 2 minutes. This is nearly 100x below the 15 ppb maximum contaminant level (MCL) in drinking water set by the Environmental Protection Agency (EPA). MEAs of various diameter and spacing were investigated to find the optimum geometry for both single and multi-element detection of Pb, Cd, Hg, Cu and Mn where results were compared with those obtained at various macro-electrode sizes. Additionally, pen-like sensors incorporating the optimized BDD working electrode, a BDD reference electrode, and BDD counter electrode were constructed and used for the detection of the aforementioned metal ions. Long-term stability of the BDD quasi-reference electrode was investigated in detail. The applicability of all electrode constructions for the detection of metal ions in drinking and environmental water samples were studied for rapid detection at home or in the field.

Figure 1
Electrochemical Detection of Sulfanilamide at MWCNT Coated Conducting Polymer Modified Electrode
Authors: Khan Shirinaz I , Chillawar Rakesh , Digal Pradesh , Motghare Ramani V
Published: February 2020

Oxidation of sulfanilamide (SN) at the Glassy Carbon Electrode (GCE) modified with a thin layer of electropolymerized Eriochrome Black-T (EBT) and multi walled carbon nanotubes (MWCNT) was investigated voltammetrically. The performance of layer by layer modified composite electrode was compared with bare GCE, p(EBT)/GCE, and MWCNT/GCE using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). An enhanced current response and lower peak potential were observed for SN oxidation at the layered composite electrode compared to rest of the electrodes. Hence, it was employed for analytical determination of SN after optimization of experimental parameters. Under optimized condition, the oxidation peak current increased linearly with concentration of SN over the range of 2 x 10-8 to 5 x 10-6 M. The limit of detection was calculated to be 1.2 x 10-8M. The electrode showed good selectivity, repeatability and reproducibility. It was also successfully applied for the determination of SN present in spiked human serum and ground water samples.

 

Keywords Sulfanilamide, MWCNT, p(EBT), composite electrode, EIS.

Figure 1
Solvothermal Preparation of Microspherical Flowerlike Ni(OH)2/Graphene Oxide Electrode for Electrochemical Capacitor Application
Authors: Khaleed Abubakar Abubakar , Bello Abdulhakeem , Dangbegnon Julien Koudio , Olaniyan Okikiola , Mwakikunga Bonex W. , Manyala Ncholu
Published: February 2020

The growing need for energy coupled with the rise in global warming and air pollution due to the burning and consumption of fossil fuels has led to an increase in alternative energy sources to meet the exponential rise in energy. Electrochemical capacitors also known as supercapacitors have attracted great attention in electrochemical energy storage application resulting from their outstanding work rate, excellent cycle life and moderate energy density. In general, they are classified into two based on the mechanism in which the store charges. Electrochemical double-layer capacitors (EDLCs) that store energy based on ion adsorption, and pseudocapacitors which store energy by the fast surface redox process. Composite of spherical Ni(OH)2/GO was synthesized via a surfactant free solvothermal technique and tested as electrodes for electrochemical capacitors. Structural and morphological analysis confirmed that incorporation of GO into Ni(OH)2 does not change the crystal structure of the pure hexagonal α-Ni(OH)2. Electrodes fabricated from the composite demonstrates a superior electrochemical performance by exhibiting a specific capacity of ∼ 420 mA h g-1 at 10 A g-1, with a corresponding rate capability of 78% when compared to that of pure Ni(OH)2, GO, and Mix-Ni(OH)2/GO. The stability study of the Ni(OH)2/GO composite exhibits a good capacity retention of ∼ 96% at a current density of 10 A g-1 after 3000 charge-discharge cycles.

Figure 1