bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrode Engineering: Impact of Processing and Design Towards Performance of Nano-Silicon Anodes
Authors: Peters Fabian , Fenske Daniela , Schmerling Marcus , Kohl Mario , Schwenzel Julian 
Published: February 2020

Silicon based materials show highest capacity among state-of-the art anode materials for LIBs and next generation batteries. Silicon anodes attract wide attention due to high specific capacity of Si, i.e. 3590mAh/g for Li15Si4 phase at room temperature.
As known, large volume changes and subsequent pulverization of brittle Si during cycling can be alleviated by using nano-sized Si particles [1]. However, the surrounding binder matrix still has to compensate large stress and strain induced by accumulated volume changes of the single particles.
The works presented here focus on the challenges on the electrode level. Choice of binder is crucial to create a matrix that can accommodate mechanical stress and strain during prolonged charge/discharge cycles. For reliable comparison of the impact of active material/binder ensembles, equal properties of electrodes (loading, porosity) are very important and hence receive special attention.
To investigate the impact of processing and electrode matrix in more detail, electrodes with high Si contents (60 to 80wt.%) and controlled, application-related loadings are produced. Characterization is carried out in laboratory sized pouch bag cells. Crucial parameters such as binder, processing, loading and voltage regime on available capacity and cycle life are discussed. Remaining reversible capacity of more than 1500mAh/gcoating (1875mAh/gSi) after 100 cycles at 0.5C is reported. Remaining electrode capacity is approx. 1.5mAh/cm² at this point.
[1]: H. Wu, Y. Cui, Nano Today (2012)

Figure 1
Storage Fading Mechanism of a Commercial 18650 Cell Comprised with Composite NMC/LMO Cathode and Graphite Anode
Authors: Wu She-huang , Lee Po-Han 
Published: February 2020

In this study, the capacities and electrochemical impedances at various states of charge (SOC) are measured after the screened commercial 18650 lithium ion cells assembled with composite cathode of layered mixed oxide (NMC) and spinel lithium manganite (LMO) and graphite anode were stored at various states of depth-of-discharge (DOD) at various temperatures for various durations. The results manifest that the capacity fading is strongly affected by the storage temperature and becomes prominent at temperatures higher than 45oC. Incremental capacity analyses (ICA) for the charge/discharge curves before and after storage were performed for the qualitative mechanism study. It demonstrates that the capacity fade of the cell stored at 60oC and 0% DOD can be attributed to the loss of active materials, and the loss of graphite anode is higher than that of composite cathode. The capacity fade of the cell stored at 60oC and 25% DOD can be caused by the lithium inventory loss, the loss of NMC, and the loss due to the morphology change of LMO. Cell stored at 50% DOD manifests similar fading behavior as that of the cell stored at 0% DOD, however, the ICA plots demonstrate that the capacity loss of the cell comes from losses of lithium inventory and NMC caused by the dissolution of transition metals with additional losses of LMO and graphite anode occur after 10 months of accumulated storage. For cell stored at 75% DOD, most the capacity loss can be due to the loss of NMC with minor contribution of lithium inventory loss, while cell stored at 100% DOD shows almost no change after storage for 12 accumulated months. These results revealed from the ICA study are consistent with those determined from the post mortem study of the electrodes obtained from cells before and after storage.
Batteries Beyond Li-Ion: Is Na-Ion a Viable Option?
Authors: Palacin M Rosa 
Published: February 2020

When we consider metal anode batteries, the density and redox potential of the metal itself are the keys to theoretical performance, with the largest figures of merit corresponding to lithium. Moving from Li to Li-ion battery technology ensures viability from a safety point of view, to the expense of a large penalty in energy density. In this case, lithium is only present as lithium ions which are the positive charge carriers in the system. When considering possible alternative M-ion technologies, the theoretical performance depends on the electrochemical capacities and operating potentials of the negative and positive electrodes. Such figures are not in any way related to the capacity values of metal anodes except for the fact that the lowest negative electrode potential limit is set by the standard redox potential of the metal itself. Thus, there is no reason why the Na-ion battery technology could not reach figures of merit comparable to those of the ubiquitous Li-ion, provided suitable electrode materials and electrolytes can be developed.
Although it had fallen into oblivion for ca. 20 years, the Na-ion battery concept is not new and trends identified during the early days of intercalation and knowledge borrowed from the Li-ion battery field should foster its progress, on condition that due attention is also paid to intrinsic differences between lithium and sodium.
The talk will review recent research carried out at ICMAB-CSIC dealing mainly with the optimization of electrolyte formulation and the study of negative electrode materials, including hard carbon prepared from sugar pyrolysis and diverse titanium containing phases, such as Na2Ti3O7. The assembly of full Na-ion laboratory cells using Na3V2(PO4)2F3 cathode, hard C anode and EC:PC:DMC based electrolyte will also be discussed. These exhibit an operation voltage of 3.65 V, very low polarization and excellent capacity retention and power performance, which are comparable to state-of-the art lithium-ion technology based on similar electrode chemistry.
Finally, the possible development of alternative M-ion technologies will also be discussed.
Intercalation As a Two-Step Process: Modeling of Adsorption at Electrochemical Interfaces in Batteries
Authors: Lück Jessica , Latz Arnulf 
Published: February 2020

Batteries based on a electrochemical lithium intercalation reaction are widely used and have many applications from costumer electronics to electromobility. Thus, insertion materials have attracted attention from practical aspects as well as fundamental interest in the exchange reaction occurring between the bulk electrode and the interface between electrode and electrolyte. Even though many reports have been published regarding bulk properties of electrolytes and insertion electrodes, like structural changes or diffusion and transport of ions in the electrode or the electrolyte, little is known about the processes at the electrolyte/electrode interface, like adsorption and desolvation on electrode surfaces. For deriving predictive models of batteries it is crucial to obtain a comprehensive understanding of the reaction mechanism taking place at the electrochemical interface.
Bruce et al. [1] proposed a 2-step-model for electrointercalation. Figure 1 shows this so called adatom model, where the fully solvated Li-ion in bulk electrolyte partially loses its solvation shell before getting adsorbed on the surface. Then it diffuses to a site, at which it can intercalate into the electrode. After this the adion loses the remaining solvent and gets incorporated in the lattice of the electrode. This proposed mechanism of a two-step-electrointercalation (desolvation/adsorption(=adion formation) and insertion) is confirmed for different insertion materials [2-4].
Considering some conversion materials like for lithium-sulfur-batteries, where Li-ions have to enter carbon spheres before reacting with sulfur, it's equally reasonable to assume first an adsorption step.
To include electrosorption, that is adsorption with partial desolvation, as an important step for intercalation and conversion reactions in batteries at the interface of a concentrated electrolyte and some active material, we derive equations for surface charges from thermodynamic and electrostatic considerations.
These derived equations are used as an intermediate step to couple the transport in the electrolyte and the solid phase with desolvation within a thermodynamic consistent reaction-transport model for Li-ion batteries [5]. Our developed model produces a reasonable coverage on the surface of the electrode while maintaining the transport properties of the cell.
[1] P.G. Bruce, et al., J. Electroanal. Chem., 322 (1992), pp 93-105.
[2] S. Kobayashi, et al., J. Phys. Chem. B, 109 (2005), pp 13322-13326.
[3] M. Nakayama, et al., J. Phys. Chem. C, 118 (2014), pp 27245-27251.
[4] M. Nakayama, et al., J. Phys. Chem. B, 107 (2003), pp 10603-10607.
[5] A. Latz, et al., Journal of Power Sources, 196 (2001), pp 3296-3302.

Figure 1.

Schematic diagram of the lithium intercalation reaction at the electrolyte – electrode interface

Figure 1
Characterization of Ionomer Thin Film Distributions in PEM Fuel Cell Catalyst Layers Using Advanced Analytical Microscopy
Authors: More Karren L. , Cullen David A. 
Published: February 2020

Polymer electrolyte membrane (PEM) fuel cell performance degradation, particularly associated with the cathode catalyst layer, can be directly attributed to the stability and durability of individual material constituents comprising the membrane electrode assemblies (MEAs), including the electrocatalyst, catalyst support, and ionomer films. The structural and chemical changes of these MEA constituents are quantified via advanced electron microscopy methods to elucidate the materials-specific degradation mechanisms contributing to performance loss, with the ultimate goal being microstructural and compositional improvements that will enhance MEA durability. Research efforts at Oak Ridge National Laboratory are focused on the high-resolution microstructural and microchemical characterization of as-fabricated fuel cell materials (e.g., the individual materials constituents and the same materials incorporated in fresh MEAs), MEAs subjected to accelerated stress tests (ASTs) designed to degrade specific MEA components, and field-aged MEAs. These studies are used to establish critical processing-microstructure-performance correlations and to elucidate the materials factors contributing to MEA degradation, performance loss, and failure. Recently, high-resolution analytical microscopy methods have been used to directly image/map the distribution and chemistry of the ionomer layers within catalyst electrodes, both on a mm-level for assessing “bulk” ionomer dispersions and at the nm-level to understand the continuity and uniformity of thin ionomer films. This presentation will focus on understanding ionomer distributions as a function of initial ionomer chemistry (e.g., solvents used), electrocatalyst content and dispersion, and type of carbon support used. Additionally, the stability of the ionomer films in cathode catalyst layers after ASTs designed for catalyst degradation and carbon corrosion will be evaluated.
________________________________________________________________________
Research sponsored by (1) the Fuel Cell Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy and (2) Oak Ridge National Laboratory’s Center for Nanophase Materials Sciences (CNMS), which is a U.S. Department of Energy, Office of Science User Facility.
Degradation Study of the Cells Operated Under Low or High Humidity Conditions at Cathode and/or Anode
Authors: Friedrich K. Andreas , Sanchez Daniel G , Ruiu Tiziana , Biswas Indro , Helmly Stefan , Schulze Mathias , Sanchez-Monreal Juan 
Published: February 2020

Water management represents one of the main challenges for the design and operation of polymer electrolyte membrane fuel cells (PEMFC), the amount of water in the cell affects the performances and degradation processes. Commonly, the main goal is try to reduce the humidification in order to simplifying the humidification system and enhancing the performance stability of the cell. However, insufficient water content can lead to increased degradation and performance loss. These negative effects depend strongly on water distribution [1] in the cell and can therefore be highly non-uniform [2]. The relation between low humidification and degradation is complex and not yet fully understood. To bring more insight into this, the differences in the local conditions of the cell must be taken into account when examining performance and degradation. Thus, in this work, particular attention is paid to the local analysis of performance and degradation of cells operated under low or high humidity conditions at cathode and/or anode.
In order to study locally the degradation influence of inlet gas humidification on cell performance all the experiments were performaned with the DLR- PCB segmented cell current density measurements, other global effect were analyzed using in-situ diagnostic tools, such as cyclic voltammetry. The changes observed locally in the current densities distributions were investigated locally by post-mortem ex-situ investigations by XPS and SEM/EDX to determine changes in the chemical composition of the different layers during the experiment.
[1] D. G. Sanchez and P. L. Garcia-Ybarra, Int. J. Hydrogen Energy, 37, 7279 (2012).

[2] D. G. Sanchez, D. G. Diaz, R. Hiesgen, I. Wehl and K. A. Friedrich, J. Electroanal. Chem., 649, 219 (2010).
The Catalytic Behaviour of Pt Clusters on Au and Pd/Au As a Function of Their Surface Coverage and Density
Authors: Al Amri Zakiya , Vasiljevic Natasa 
Published: February 2020

Pt bimetallic structures such as Pt core-shell layers, alloys and clusters on different substrates have been a focus of intense research because they generally exhibit properties different from bulk Pt. The often improved catalytic activity of these structures makes them highly attractive for fuel cells applications[1].
Our understanding and decoupling of the effects responsible for the enhanced catalytic behaviour, such as bi-functional, electronic and ensemble effects, is incomplete. Numerous studies have been conducted so far with the aim of correlating surface activity with the structure and distribution of Pt on or in the catalyst surface [2-5]. It has been shown that the catalytic activity of Pt nanoparticles decorated with ruthenium clusters (Ru/Pt catalyst) is twice that of the commercial 50 : 50 Ru/Pt alloy catalyst [2]. An enhancement of CO tolerance has been also found on supported Pt/Ru catalyst obtained by spontaneous deposition for a considerably lower Pt loading than in commercial catalyst[3]. The modified Au surface with Pt nanosize clusters [6] coverage as low as 15-25% of the substrate area, exhibit very high activity and incredible selectivity toward dehydrogenation of formic acid (HCOOH).
Our interest in this work are 2-dimensional model systems of Pt clusters electrodeposited on Au and Pd/Au. We used different electrochemical protocols to control Pt clusters’ size, i.e. in terms of diameter, height and distribution: i) spontaneous adsorption of [PtCl4]2- complex and its potential controlled reduction e.g. the method often called ‘spontaneous deposition’ (SD) [2, 7] and ii) modified surface limited redox replacement (SLRR) method based on the galvanic replacement or partial underpotentially deposited metal layers. For each method successive application of optimized electrodeposition protocols yielded increased Pt surface coverage ranging from 0.25 to 1 area fraction. The surface coverage of Pt/Au and Pt/Pd/Au as well as the active area were determined electrochemically using H-UPD and CO-adsorption. The Pt clusters structure such the diameter, height and distribution were examined by scanning tunnelling microscopy (STM). The catalytic behaviour of Pt- nanostructures is analysed during HCOOH electro-oxidation and it is illustrated in the figure bellow.

References

1. M. Debe, Nature, 2012. 486: 43.
2. W. Chrzanowski; H. Kim and A. Wieckowski, Catal. lett., 1998. 50: 69.
3. S. Brankovic; J. McBreen and R. Adzic, J. Electroanal. Chem., 2001. 503: 99.
4. S. Bae; D. Gokcen; P. Liu; P. Mohammadi and S. Brankovic, Electrocatal., 2012. 3: 203.
5. B. Du and Y. Tong, Phys. chem. lett., 2005. 109(38): 17775.
6. M. Obradović; A. Tripković and S. Gojković, Electrochim. Acta, 2009. 55: 204.
7. Chrzanowski and Wieckowski, Langmuir, 1997. 13: 5974.

Figure 1
Evaluation of Activity of Platinum-Ruthenium-Cobalt/Graphene Catalysts Towards Methanol Oxidation
Authors: Semasko Miroslav , Tamasauskaite-Tamasiunaite Loreta , Kepeniene Virginija , Balciunaite Aldona , Vaiciuniene Jurate , Drabavicius Audrius , Norkus Eugenijus 
Published: February 2020

A simple approach – microwave synthesis was used to prepare platinum-ruthenium-cobalt/graphene catalysts (denoted as Pt-Ru-Co/GR). A series of Pt-Ru-Co/GR with the different molar ratios were prepared by microwave-assisted heating of the reaction mixture consisting of H2PtCl6, RuCl3, CoCl2 and ethylene glycol. The Transmission Electron Microscopy (TEM) and Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) were employed to characterize the synthesized Pt-Ru-Co/GR catalysts. The electrocatalytic activity of the synthesized catalysts towards the oxidation of methanol and CO was investigated by means of cyclic voltammetry and chrono-techniques. The electrochemically active surface areas of the prepared catalysts were determined from the cyclic voltammograms of the Pt-Ru-Co/GR catalysts recorded in a deaerated 0.5 M H2SO4 solution at a sweep rate of 50 mV s–1 by calculating the charge associated with hydrogen adsorption (220 µC cm-2).
It was found that the Pt-Ru-Co/GR catalysts with the Pt:Ru:Co molar ratios equal to 1:2:2, 1:1.7:5.6 and 3.5:1:23 were prepared. The EDX analysis confirm the presence of Pt, Ru and Co nanoparticles in the investigated PtCoRu/GR catalysts.
It has been determined that the Pt-Ru-Co/GR catalyst with the Pt:Ru:Co molar ratio equal to 3.5:1:23 has a higher electrocatalytic activity towards the oxidation of methanol in acidic medium as compared with that of other synthesized catalysts.
Mixed Reactant Low Temperature Fuel Cells: The Swiss-Roll Cell Design and Selective Electrocatalysts
Authors: Gyenge Elod L. 
Published: February 2020

Eliminating the proton exchange membrane (PEM) together with the platinum-based anode and cathode catalysts and replacing the bulky bipolar plates with lighter and flexible alternatives, would significantly improve the economic outlook of low temperature fuel cells operated with liquid fuels. To address the afore-mentioned issues of PEM fuel cells, at the University of British Columbia we have developed a novel mixed reactant fuel cell design referred to as the Swiss-roll cell, fed with a two-phase mixture of liquid fuel and air (or oxygen) [1-5]. Here, a research progress review is presented related to both selective electrocatalysis and Swiss-roll cell engineering applied to two alkaline fuel cell systems: sodium borohydride – oxygen and sodium borohydride – nitrous oxide, respectively. On the anode, the borohydride electro-oxidation reaction is a complex, up to eight electron transfer process, with possibly competing hydrogen evolution generated by either faradaic (i.e., electrocatalytic) or non-faradaic (i.e., thermocatalytic) pathways. Experimental results correlated with density functional theory modelling predictions are discussed focused on the borohdyride electro-oxidation mechanism on catalysts such as: Pt, Au and Os. On the cathode side, in case of the oxygen reduction reaction (ORR) in alkaline media the comparative performance of gas diffusion electrodes with electrocatalysts such as MnO2, Ag and Fe-aminoantypyrine (Fe-AAPyr) is presented. For nitrous oxide reduction, the electrode kinetics on Pd and Pt electrocatalysts are compared. It is shown that the selective electrocatalyst discovery combined with cell electrochemical engineering innovations enables significant improvements in the power output, reaching 250 mW/cm2 for the membrane-free Swiss-roll mixed-reactant direct borohdyride fuel cell operated at 50 0C and near atmospheric pressure using non-platinum anode and cathode catalysts.
References:

A. Aziznia, C. Oloman and E.L. Gyenge,
J.Power Sources

, 212, 154-160 (2012).

A. Aziznia, C. Oloman and E.L. Gyenge,
ChemSusChem
, 6, 847-855 (2013).

A. Serov, A. Aziznia, P. H. Benhangi, K. Artyushkova, P. Atanassov and E. Gyenge,
J. Mat. Chem. A,

1, 14384-14391, (2013).

A. Aziznia, C. Oloman and E.L. Gyenge,
J.Power Sources
, 265, 201-213 (2014).

C. W. Oloman, British Patent GB 2474202, 2012.

Figure 1
Analytical Model for the Interdigitated Flow Field
Authors: Milshtein Jarrod David , Darling Robert M. , Bazant Martin Z. , Brushett Fikile R. 
Published: February 2020

Flow fields in low-temperature fuel cells and redox flow batteries play the important role of facilitating reactant transport to porous electrode surfaces, where power-converting electrochemical reactions occur1. Of the four major flow field design categories (flow-through, parallel, serpentine, and interdigitated flow fields (IDFF)), the IDFF has demonstrated high current densities with only a moderate pressure drop. Although many studies have noted the performance enhancements offered by the IDFF, development has been limited to application-specific numerical or empirical studies2–4; no bottom-up design rules exist. This lack of design principles stems from an inability to analytically model species flux and flow profile through the complicated IDFF geometry. As such, this study offers the first analytical solution of the velocity and reactant distributions through a two-dimensional (2-D) IDFF.
The flux of a species through the IDFF channel can be described by the Nernst-Planck equation in porous media, which is a conformally invariant mathematical function5. Thus, it is possible to achieve an analytical expression for reactant flux and / or streamlines through the IDFF via the method of conformal mapping
5. Through this strategy, the combined migration-diffusion-advection problem can first be solved in a straight channel, and then the straight-channel solution is mapped (Figure 1) to the more complicated IDFF geometry by exploiting the Schwarz-Christoffel transformation5. The original numerical 2-D model by Kazim et al. is solved in this work, analytically2; Figure 2 shows a representative velocity magnitude profile for an IDFF electrode cross section. Due to unwieldy equations which arise from the analytical construction, dimensionless numbers are developed to provide an intuitive understanding of transport relationships in the IDFF, and limiting cases of electrode thickness are considered. Ultimately a convenient framework for IDFF design rules is developed by analytically solving the transport equations, allowing for greater insight to system design.

Acknowledgements

We would like to acknowledge the financial support of the Joint Center for Energy Storage Research and the United States National Science Foundation Graduate Research Fellowship program.

References

1. X. Li and I. Sabir, Int. J. Hydrog. Energy, 30, 359–371 (2005).
2. A. Kazim, H. T. Liu, and P. Forges, J. Appl. Electrochem., 29, 1409–1416 (1999).
3. Y. Wang, S. Basu, and C.-Y. Wang, J. Power Sources, 179, 603–617 (2008).
4. R. M. Darling and M. L. Perry, J. Electrochem. Soc., 161, A1381–A1387 (2014).
5. M. Z. Bazant, Proc. R. Soc. Math. Phys. Eng. Sci., 460, 1433–1452 (2004).

Figures

Figure 1