Accepted Manuscripts

Technical Brief  
Atef Y. Shenouda and Mustafa M. S. Sanad
J. Electrochem. En. Conv. Stor.   doi: 10.1115/1.4036318
Li2NixFe1-xSiO4 (x= 0, 0.2, 0.4, 0.6, 0.8 and 1) samples were prepared by sol-gel process. The crystal structure of prepared samples of Li2NixFe1-xSiO4 was characterized by XRD. The different crystallographic parameters such as crystallite size and lattice cell parameters have been calculated. SEM and FT-IR investigations were carried out explaining the morphology and function groups of the synthesized samples. Furthermore, electrochemical impedance spectra measurements are applied. The obtained results indicated that the highest conductivity is achieved for Li2Ni0.4Fe0.6SiO4 electrode compound. It was observed that Li/Li2Ni0.4Fe0.6SiO4 battery has initial discharge capacity of 164 mAhg-1 at 0.1 C rate. The cycle life performance of all Li2NixFe1-xSiO4 batteries were ranged between 100 and 156 mAhg-1 with coulombic efficiency range between 70.9 and 93.9%. Keywords: Positive electrodes; Lithium metal silicates; electrical conductivity; Cyclic performance.
TOPICS: Electrical conductivity, Spectra (Spectroscopy), Crystal structure, Metals, Electrodes, Optimization, Cycles, Lithium, Sol-gel processing, Batteries, Lithium-ion batteries
Mohammad Yaghoub Abdollahzadeh Jamalabadi
J. Electrochem. En. Conv. Stor.   doi: 10.1115/1.4036278
In this paper the electrochemical impedance spectroscopy (EIS) method is applied through a transient in solid oxide fuel cell (SOFC) to obtain the dynamic modelling. Instead of measuring the current response of a fuel cell to a small sinusoidal perturbation in voltage at each frequency, the Hammerstein-Wiener model identification method is applied through a one transient who leads to the significant decrease of computational costs. Dynamic responses are determined as the solutions of coupled partial differential equations derived from conservation laws of charges, mass, momentum and energy with electrochemical kinetics by using Butler-Volmer model and gas diffusion on the extended Maxwell-Stefan species equations or dusty gas model (DGM). Because the system consisted of electrical and mechanical components, the behaviour of the system was nonlinear. The obtained results are in qualitative good agreement with experimental data published in literatures showed the effectiveness of the propose model. Finally a parametric study based on the obtained model is performed to study the effects of channel length, inlet H2 concentration, inlet velocity and cell temperature in Nyquist plots and the voltage responses to step changes in the fuel concentration and load current. The model can be useful as a benchmark for illustrating different designs and control schemes.
TOPICS: Solid oxide fuel cells, Electrochemical impedance spectroscopy, Transients (Dynamics), Fuel cells, Dynamic response, Partial differential equations, Dynamic modeling, Momentum, Temperature, Diffusion (Physics), Fuels, Stress
Review Article  
Rahul Gopalakrishnan, Shovon Goutam, Luis Miguel Oliveira, Jean-Marc Timmermans, Noshin Omar, Maarten Messagie, Peter Van den Bossche and Joeri van Mierlo
J. Electrochem. En. Conv. Stor.   doi: 10.1115/1.4036000
This paper provides an extended overview of the existing electrode materials and electrolytes for energy storage systems, that can be used in environmental friendly hybrid and electric vehicles from the literature based on lithium-ion and non-lithium technologies. The performed analysis illustrates the current and future evolution in the field of electrode materials development (2015 – 2040). The investigated characteristics are specific energy, specific power, cycle life and safety. Furthermore, the proposed study describes the cost and life cycle assessment of the proposed technologies and the availability of these materials.
TOPICS: Energy storage, Lithium, Electrodes, Thermodynamic power cycles, Electric vehicles, Electrolytes, Safety, Life cycle assessment
Mohammadreza Nazemi, Jiankai Zhang and Marta C. Hatzell
J. Electrochem. En. Conv. Stor.   doi: 10.1115/1.4035835
There is an enormous potential for energy generation from the mixing of sea and river water at global estuaries. Here we present a novel approach to convert this source of energy directly into hydrogen and electricity using Reverse electrodialysis (RED). RED relies on converting ionic current to electric current using multiple membranes and redox based electrodes. A thermodynamic model for RED is created to evaluate the electricity and hydrogen which can be extracted from natural mixing processes. With equal volume of high and low concentration solutions (1L), the maximum energy extracted per volume of solution mixed, occurred when the number of membranes is reduced, with the lowest number tested here being 5 membrane pairs. At this operating point, 0.32 kWh/m3 extracted as electrical energy and 0.95 kWh/m3 as hydrogen energy. This corresponded to an electrical energy conversion efficiency of 15%, a hydrogen energy efficiency of 35% and therefore a total mixing energy efficiency of nearly 50%. As the number of membrane pairs increases from 5 to 20, the hydrogen power density decreases from 13.6 W/m2 to 2.4 W/m2 at optimum external load. In contrast, the electrical power density increases from 0.84 W/m2 to 2.2 W/m2. Optimum operation of RED depends significantly on the external load (external device). A small load will increase hydrogen energy while decreasing electrical energy. This trade-off is critical in RED optimization for both hydrogen and electricity generation.
TOPICS: Energy generation, Hydrogen production, Hydrogen, Membranes, Stress, Energy efficiency, Energy conversion, Electrodes, Optimization, Electric power generation, Density, Electricity (Physics), Electric current, Water, Seas, Rivers, Power density, Tradeoffs
William A. Rigdon, Travis J. Omasta, Connor Lewis, Michael A. Hickner, John R. Varcoe, Julie N. Renner, Katherine E. Ayers and William E. Mustain
J. Electrochem. En. Conv. Stor.   doi: 10.1115/1.4033411
Fossil fuel power plants are responsible for a significant portion of anthropogenic atmospheric carbon dioxide (CO2) and due to concerns over global climate change, finding solutions that significantly reduce emissions at their source has become a vital concern. When oxygen (O2) is reduced along with CO2 at the cathode of an anion exchange membrane (AEM) electrochemical cell, carbonate and bicarbonate are formed which are transported through electrolyte by migration from the cathode to the anode where they are oxidized back to CO2 and O2. This behavior makes AEM-based devices scientifically interesting CO2 separation devices or “electrochemical CO2 pumps.” Electrochemical CO2 separation is a promising alternative to state-of-the-art solvent-based methods because they operate at low temperatures and scale with surface area, not volume, suggesting that industrial electrochemical systems could be more compact than amine sorption technologies. In this work, we investigate the impact of the CO2 separator cell potential on the CO2 flux, carbonate transport mechanism and process costs. The applied electrical current and CO2 flux showed a strong correlation that was both stable and reversible. The dominant anion transport pathway, carbonate vs. bicarbonate, undergoes a shift from carbonate to mixed carbonate/bicarbonate with increased potential. A preliminary techno-economic analysis shows that despite the limitations of present cells, there is a clear pathway to meet the US DOE 2025 and 2035 targets for power plant retrofit CO2 capture systems through materials and systems-level advances.
TOPICS: Carbon dioxide, Dynamics (Mechanics), Low temperature, Separation (Technology), Anodes, Sorption, Electric current, Power stations, Pumps, Electrolytes, Membranes, Oxygen, Fossil fuel power station, Carbon capture and storage, Climate change, Emissions, Electrochemical cells

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