bluuebunny/crossref_metadata_2025_split huggingface dataset:
Understanding Membrane Degradation Mechanisms Under Heavy Duty Fuel Cell Conditions: A Multi-Disciplinary Approach
Authors: Malek Kourosh , Kjeang Erik , Holdcroft Steven , Eikerling Michael , Djilali Ned , Knights Shanna 
Published: February 2020

The Automotive Partnership of Canada (APC) project on Next-Gen Heavy Duty Fuel Cell Buses is a government supported three-year project dedicated to research and product development of next generation heavy duty fuel cell buses in Canada (www.apc-hdfc.ca). The project represents a collaborative effort between Ballard Power Systems, Simon Fraser University and University of Victoria in British Columbia, Canada. The overarching objective is fundamental understanding of membrane degradation mechanisms, degradation rates, and failure modes under drive cycles and conditions that are typical for heavy duty vehicle operation. The aim is to help develop next generation fuel cell technology that is equivalent to or surpasses incumbent diesel engines in terms of durability and reliability, while reducing capital and warranty costs.
In order to develop new durable membrane technologies and devise mitigation strategies to reach desired membrane lifetime, empirical and physical models need to be developed and employed. In this context, understanding the relationship between operation mode and membrane degradation under heavy duty fuel cell conditions is of vital importance. Apart from mechanical degradation such as thinning and pinhole formations, chemical and electrochemical degradation could also take place in perfluorosulfonated acid (PFSA) ionomer membranes. Due to complexity of the underlying processes, degradation mechanisms and their dependence on relevant operating conditions are not generally well established.
We present results from an extensive effort that integrates multi-scale, multi-disciplinary modeling with large–scale accelerated degradation testing data. Results are analysed in view of the relative importance of various membrane degradation mechanisms via various chemical and mechanical processes. The versatile multi-scale modeling framework includes structure formation at molecular/meso-scales, water sorption characteristics, kinetics, as well as continuum modelling of chemical and mechanical degradation processes.

References

[1] F. de Bruijn, et al., Fuel Cells 8(1), 2008, 3–22
[2] Cheng Chen, T. F. Fuller, Modeling of Hydrogen Peroxide Formation in PEMFCs, Electrochim. Acta, 54, 3984-3995 (2009).
[3] N. Macauley, L. Ghassemzadeh, C. Lim, M. Watson, J. Kolodziej, M. Lauritzen, S. Holdcroft, E. Kjeang, “Pt Band Formation Enhances the Stability of Fuel Cell Membranes”, ECS Electrochemistry Letters, 2(4) (2013) F1-F3.
[4] L. Ghassemzadeh, S. Holdcroft, "Quantifying the structural changes of PFSA ionomer upon reaction with hydroxy radicals”, JACS, 2013, 135 (22) (2013), 8181-8184.
[5] R. M.H. Khorasany et al., “On the Constitutive Relations for Catalyst Coated Membrane Applied to In-Situ Fuel Cell Modeling”, 2013, submitted.

Fig. 1: APC project on heavy duty bus fuel cells (www.apc-hdfc.ca).
The Study of Indirect Electroreductive Cyclisation of Propargyl Derivatives Using [Ni(tmc)]Br2 As Catalyst in Ionic Liquids
Authors: Medeiros M. J. , Neto M. J. , Esperança J.M. S.S. , Esteves A. P. , Silva M. M. 
Published: February 2020

Five-membered heterocyclic compounds are among the most important natural biologically active compounds. X-heterocycles (X = O, N) are usually synthesised by radical cyclisation methodology [1] based on organotin hydrides which are toxic and also troublesome to separate from the reaction products.
A convenient alternative to synthetic methods involving organometallic hydrides is the use of electrogenerated nickel(I) complexes as mediators for cathodic intramolecular cyclisations [2]. This methodology proved to be successful in the formation of carbocyclic products and substituted tetrahydrofurans. Such work has largely used aprotic organic solvents such as DMF which presents some toxicity.
Due to an increasingly “green”-conscious industrial community, researchers have started to examine more eco-friendly and sustainable chemical processes. Ionic liquids (ILs) represent a class of alternative solvents currently receiving serious consideration with the promise of both environmental and technological benefits [3].
A number of room-temperature ILs has been synthesized, characterized and applied in organic synthesis and catalyzed processes. Their characteristics render them promising replacements for volatile organic solvents (VOCs), which are a source of environmental problems.
In the present work, the reductive intramolecular cyclisation of bromopropargyloxy esters catalysed by electrogenerated (1,4,8,11-tetramethyl-1,4,8,11-tetraaza-cyclotetradecane)nickel(I), [Ni(tmc)]+ as the catalysts in ILs, N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide, [N1 1 1 2(OH)][NTf2] and 1-ethyl-3-methylimidazolium ethylsulfate, [C2mim][C2SO4] has been investigated by cyclic voltammetry and controlled-potential electrolysis. During controlled-potential electrolyses of solutions of Ni(II) complexes in the presence of bromopropargyloxy and bromoallyl derivatives, catalytic reduction of the latter proceeds via cleavage of the carbon–bromine bond to form a radical intermediate that undergoes cyclization to afford the substituted tetrahydrofurans [4].

ACKNOWLEDGEMENTS

We are grateful to the Fundação para a Ciência e Tecnologia (PEst-C/QUI/UI0686/2011) for financial support of this work.

REFERENCES

[1] B. Giese, “Radicals in Organic Synthesis: Formation of Carbon-Carbon Bonds”, Pergamon Press, Oxford, 1986.
[2] E. Dunach, M.J. Medeiros, S. Olivero, New J. Chem., 30, 1534 (2006).
[3] Ionic liquids IIIB: Fundamentals, Process, Challenges, and Opportunities, ACS Symp. Ser. (Eds.: R. D. Rogers and K. R. Seddon), ACS, Washington DC, 2005.
[4] 5. P.K. Mandal, G. Maiti, S.C. Roy, J. Org.
Chem., 63, 2829 (1998).
Optimization and Constant Capacity Cycling of the Core-Shell Carbon Silicon Composite Anode for Lithium Ion Batteries
Authors: Wen Hao , Soltis Richard , Karulkar Mohan 
Published: February 2020

Accommodating the 3-fold volume expansion of silicon during lithiation is necessary to take advantage of its 10-fold larger capacity compared to industry-standard graphite. 1In this report, we describe recent experiments at using core- -shell C-Si composites that showed significant improvements in cycling performance over conventional C-Si composites.
The core- -shell structure is evident in FESEM, as shown in Figure 1. The ~100 nm Si cores are encapsulated inside larger carbon shells, leaving ~50 nm of hollow space. Previous studies showed that these structures are capable of accommodating the volume expansion of Si during lithiation without distorting the carbon shell, while maintaining a stable SEI layer.2Thermal gravimetric analysis showed that Si constitutes 75 wt% of the composite, close to the nominal 77 wt% as calculated from synthesis procedure.
Cycling to a fixed capacity of 1000 mAh/g, the cycling efficiency of the composite anode was mostly above 90% after the initial SEI formation, as shown in Figure 2. After the first cycle, subsequent cycling loops appeared to have a consistent shape, indicating reversible reaction chemistry.
Optimization of the core-hollow-shell composite is achieved by fine-tuning the fabrication process and cycling conditions. Constant capacity cycling controls the state of charge by limiting the integrated charge flow into the cell. The cutoff state of charge and the current density both have a significant effect on the cell performance. XRD reveals factors contributing to the irreversible charge loss at every cycle.
Improvement of the homogeneity of chemical coating and mixing was also studied. The precursor polymer used to produce the coating of carbon on the silicon nanoparticles directly impacts the geometry of the final product. The procedure for etching away the silicon dioxide shell with hydrofluoric acid was improved as well.

Reference

1. Li, X. & Zhi, L. Managing voids of Si anodes in lithium ion batteries. Nanoscale(2013). doi:10.1039/c3nr03197g
2. Liu, N. et al. A yolk-shell design for stabilized and scalable li-ion battery alloy anodes. Nano Lett.
12, 3315–21 (2012).
Silicon Nanowires and Nanotrees Electrodes for Pseudocapacitors
Authors: Sadki Said , Thissandier Fleur , Aradilla David , Berton Nicolas , Gentile Pascal , Bidan Gérard , Brousse Thierry 
Published: February 2020

Supercapacitors integration in micro-electronic circuit should improve portable devices efficiency [1] and be easier with silicon (Si) electrodes. In our previous work we have realized highly doped Si nanowires (SiNWs) micro-supercapacitor (µ-SC) electrodes showing quasi ideal capacitive behavior [2, 3]. This works studies the elaboration and characterization of highly doped Si nanotrees (SiNTrs) µ-SC and SiNWs micro-pseudocapacitors electrodes. It focuses on our recent advances on SiNTrs growth and use in µ-SC.
SiNWs and SiNTrs are grown by CVD on highly doped Si via localized gold catalysis. SiNTrs are grown either by two CVD growths separated by a new gold deposition, or by a single growth in which an annealing (gold pours along NWs) separates trunks and branches growths [4, 5]. Electrochemical properties are evaluated in organic electrolyte (1M, NEt4BF4, PC) and ionic liquid (EMI-TFSI) by EIS, cyclic voltametry and galvanostatic charge/discharge. For PC PEDOT films was electrodeposited on SiNWs.
As seen previously, electrode capacity increases with the electrode developed surface, i.e. SiNWs length, density and SiNTrs branches. SiNTrs are tuned by fitting HCl gas ratio during trunk growth, annealing time and temperature. Doping gas/silane ratio monitors their doping level. Highly doped, dense, hyperbranched (L ≈ 3 µm, Ø ≈ 30 nm), 40 µm long SiNTrs electrodes have a 950 µF.cm-2 capacity, i.e. about 158 fold bulk Si one and twice 50µm long SiNWs electrode one. SiNTrs/SiNTrs µ-SCs show highly stable cycle efficiency (97 %) and capacity over at least 100 000 cycles for current densities ranging from 5 to 500 µA.cm-2. Using ionic liquid as electrolyte improves devices voltage and thus performances.
[1] J.R. Miller, P. Simon, Science, 2008, 321, 651
[2] F. Thissandier, and al, Electrochem. Comm., 2012, 25, 109
[3] F. Thissandier, and al, Nanoscale Res. Lett., 2012, accepted
[4] P. Gentile, and al, Nanotechnol., 2008, 19, 125608
[5] R. Maboudian, and al, J. Mater.
Chem., 2008, 18, 5376
Improvements in Li Air Batteries through Electrocatalysts, Electrode Structure Design and Modelling
Authors: Scott Keith , Cheng Hua , Sahapatsombut Ukrit 
Published: February 2020

Rechargeable Li-air batteries allow Li+ and e- in the cell to react with O2 from the air and enable an increase in storage capacities up to 10 times cf. with Li ion. The air cathode is a new challenge for the battery. New nanostructured air cathode materials were fabricated, characterised by using XRD, TEM and SEM and tested as cathodes in rechargeable Li-air batteries. Such 3D nanomaterials displayed high capacity (up to 3000 mAhg-1). The superior performance of the nanomaterials was attributed to their structures which acted as transport pores The relationship between composition, especially ratios of catalyst to carbon, structure, properties and performance shall be discussed. Measures to tackle technical barriers in battery design and engineering will also be addressed. We have investigated the use of bifunctional MnO2/Au catalysts. This has provided significant improvement in its stability (stable cycling > 100) as well as a great improvement in the lithium air cell capacity (10,000mAh/g).
Battery performance is still affected by loss in capacity after repeated cycling due to instability of certain solvents and cathode carbon supports and ingress of CO2. A micro-macro homogeneous mathematical model was developed for the cycling operation of a porous Li-air cathode using concentrated binary electrolyte theory. The model includes mechanism for solvent degradation and production of Li carbonates. The physical and chemical property data is carefully applied in this model to predict the time dependance of electrolyte concentration, non-uniform porosity and reaction rate and loss of capacity after cycling. Alternative modes of battery operation are explored to improve power and energy density performance
Comparison Study of Various Anode Materials for Li-Ion Capacitors
Authors: Tropy Nolan Lance , Cao Wanjun , Zheng Jim P. 
Published: February 2020

Lithium-ion Capacitors (LICs) have attracted much attention as a new power source due to its high energy density compared to conventional electric double-layer capacitors (EDLCs), and its high power density compared to batteries as well as having the long cycle life. Recently, some research work1-2 in our group has been done on LICs. In this abstract, various carbon material anode electrode including hard carbon, soft carbon and graphite were studied and compared for the Li-ion Capacitors application.
To compare the hard carbon, soft carbon and graphite, three Li-ion capacitor full cells with these carbon electrodes were assembled to compare the power and cycle performance. Figure 1 presents the voltage profiles of the LIC full cells with various carbon electrodes. It can be seen that the swing potential of hard carbon and soft carbon anode electrodes is in a wider range than graphite electrodes. The swing potential range of hard carbon and soft carbon negative electrodes is 0.2-0.4 and 0.4-0.7 V vs. Li/Li+, respectively; which are above 0 V vs. Li/Li+ and can suppress the formation of lithium dendrites in anode to a large extent. On the other side, the potential plateau of graphite anode electrode is near 0 V vs. Li/Li+, which increases the possibility for lithium dendrites to form and short the LIC cells.
The LIC full cells with various carbon electrodes were also tested in Figure 2. This was done in order to compare the energy, power and cycle performance. It can be obviously observed from Figure 2(a) that LIC full cell with hard carbon electrode displays both higher energy density and higher power density than the cells with soft carbon and graphite. For the cycle performance as shown in Figure 2(b), after 1000 cycles, the LIC cell with hard carbon can retain up to 100% while the LIC cells with soft carbon and graphite only retain up to 80% and 78% of the initial discharge energy density, respectively. Based on the evaluation of the electrochemical properties including energy, power and cycle performance of the various carbon electrodes, it is concluded that hard carbon is the best option for negative electrode, as it displays a higher energy density, power density and longer cycle life implemented in two-electrode Li-ion capacitor systems.

References

1. W.J. Cao, J.P. Zheng, J. Power Sources, 213, 180 (2012).
2. W.J. Cao and J.P. Zheng, J. Electrochem. Soc. 160, A1572 (2013).
A Combined Investigation into the Effect of Ni/Mn/Co Ions on Lithium-Ion Battery Anodes Using X-Ray Photoelectron Spectroscopy and Secondary Ion Mass Spectrometry
Authors: Nitta Naoki , Benson Jim , Lee Jung Tae , Kovalenko Igor , Tighe Sean , Fuller Thomas F. , Yushin Gleb 
Published: February 2020

Nickel Cobalt Manganese (NCM) cathodes utilize the combination of transition metal ions to achieve good specific capacity, voltage, and safety characteristics, and are among the best performing of industrially produced cathode materials. However, Mn is known to escape the cathode via a disproportionation reaction as Mn2+, and has been detected on the anode solid electrolyte interface (SEI). Furthermore, batteries incorporating Mn in the cathode are known to have a reduced cycle life due to increased impedance (1). A recent study of Lithium Manganese Oxide (LMO) cathodes reveals the Mn to stay in the 2+ oxidation state (2), but little is otherwise known about the role of Mn in the SEI layer.
To analyze the effect of the SEI on the degradation of NCM full cells, the authors previously analyzed anodes taken from commercial NCM batteries of varying degrees of degradation (3). X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) were used along with other techniques to analyze the presence of elements in the SEI as a function of depth. However, analysis of chemical species was complicated by the presence of PVDF binder, air exposure of the sample, and ion implantation/chemical decomposition due to exposure to a high energy ion beam.
In this study, the effect of temperature, cycling, and the presence of transition metal ions were studied in thin film half cells. Ni2+, Mn2+, and Co2+ion salts were each introduced, as these ions all dissolve into the electrolyte from NCM cathodes and have been detected in the SEI (4,5). A thin film carbon anode was used to obviate the binder, and allow clearer chemical analysis and depth profiling. XPS analysis was used to reveal chemical information about the SEI, while SIMS was used to provide a depth profile.
XPS analysis showed an increase in LiF composition with the number of charge/discharge cycles for all cells, but otherwise indicated a chemically different SEI when the salts are added. SIMS analysis showed the presence of Ni/Co/Mn ions and other species through the depth of the SEI layer. By combining these two methods, the character of the SEI with and without the transition metal ions was hypothesized.
REFERENCES

M. Wohlfahrt-Mehrens, C. Vogler, J. Garche, J. Power Sources
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C. Zhan, J. Lu, A. Jeremy Kropf, T. Wu, A. N. Jansen, Y.-K. Sun, X. Qiu, K. Amine, Nat. Commun.
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52, 388-397 (2012).

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11, A226-A228 (2008).

H. Zheng, Q. Sun, G. Liu, X. Song, V. S. Battaglia, J. Power Sources
207, 134-140 (2012).
Spinel NiCo2O4 As a Promising Electrode Material for Li-Ion and Li-O2 Batteries
Authors: Jadhav Harsharaj S. , Park Chan-Jin 
Published: February 2020

Secondary Li-ion batteries have played an important role as an energy storage device for portable electronics and electric/hybrid electric vehicles (EV/HEV). However, the energy density of conventional Li-ion battery is not sufficient, and thus a Li-O2 battery can be a potential alternative to Li-ion batteries due to its much higher energy density.
In addition, transition metal oxides with nanostructural characteristics have shown good performance due to their advantage of high surface to volume ratio and short length for Li-ion diffusion in comparison with their bulk counterparts. Previous studies showed that the spinel NiCo2O4 is an excellent candidate as an electrode material for Li-ion and Li-air batteries. NiCo2O4, a well-known cobalt-nickel spinel oxide, owns two solid-state redox couples (Co3+/ Co2+ and Ni3+/Ni2+) in the structure, which enables to exhibit a remarkable elctrocatalytic activity. In the present study, we have investigated the electrochemical performance of spinel NiCo2O4, as an anode material for Li-ion battery and cathode material for Li-O2 battery.
In the present study, spinel NiCo2O4 has been synthesized by simple and inexpensive urea assisted co-precipitation method and subsequent annealing at 400 oC for 2h.The TG and DSC analysis was carried out to analyze the weight loss during heat treatment. The spinel structure of NiCo2O4 was confirmed by the X-ray diffraction (XRD) analysis. The FE-SEM analysis reveals the formation of spinel NiCo2O4 with urchin like structure, composed of several nanorods. The nanorods are highly porous consisting of interconnected nanoparticles confirmed by TEM analysis. The N2 adsorption-desorption was carried out to investigate the surface area and porosity of spinel NiCo2O4. The electrochemical investigation of spinel NiCo2O4 as an anode material for Li-ion showed excellent cyclability (~1020 mAh.g-1 at 0.2C upto 200 cycles) and superior rate capability. The use of spinel NiCo2O4 as cathode material in Li-O2 cell, exhibit an excellent performance reasonable specific capacity, and lower overpotential. In conclusion, Spinel NiCo2O4 can be a potential candidate as an electrode material for Li-ion and Li-air batteries.
Synthesis of ZnO@Ni(OH)2 Nanostructures for Application in High-Performance Supercapacitors
Authors: Luo Yi-Hsiang , Liao Yun-Wen , Wang Jun-Yi , Huang Jin-Hua 
Published: February 2020

Recently, supercapacitor has become a preferred energy storage device because it has higher power density than batteries and higher energy density than conventional capacitors and fast charge/discharge rates. Among the often used supercapacitor electrode materials, pseudocapacitive metal oxide exhibits much high capacitance, but the poor electrical conductivity limits its performance. In order to overcome this disadvantage, one dimensional ZnO nanowires (NWs) are widely employed because they can serve as a direct electrical pathway for electrons and provide a larger surface area for loading metal oxide. [1]

Base on above considerations, in this work, we fabricated the Ni(OH)2 coated ZnO electrodes for use in supercapacitors. As shown in Fig. 1, the Ni(OH)2 coated ZnO electrode consists of upstanding nanowires (NWs) and outstretched Ni(OH)2flakes grown all over each nanowire.
First, ZnO NWs was grown by immersing the seeded FTO substrate in aqueous solutions containing 0.01 M zinc acetate dihydrate and 0.01 M hexamethylenetetramine (HMTA) at 90 oC for 5 h. These ZnO NWs were then used as the trunks for the growth of Ni(OH)2 flakes. The Ni(OH)2 flakes were synthesized by the pulse galvanostatic electrodeposition onto the surface of ZnO NWs in aqueous solution of 5 mM nickel nitrate hexahydrate for 2 min at room temperature. The parameters of pulse galvanostatic electrodeposition include current density, pulse time (ton), and relaxation time (toff), the optimized conditions for pulse galvanostatic electrodeposition are 1 mA/cm2, 1 s, and 10 s respectively.
We have achieved a high specific capacitance 1827 F/g at a discharge current density of 2 A/g, corresponding discharge curves are shown in Fig. 2. Fig. 3 reveals the highest energy density and power density are 185.0 Wh/kg and 9.0 kW/kg, respectively. Effects of current density, ton, toff, and deposition time on the performance of supercapacitors were investigated.
Reference

Y. B. He, G. R. Li, Z. L. Wang, C. Y. Su, Y. X. Tong, Energy Environ. Sci., 2011, 4, 1288-1292.