Gas diffusion layer (GDL) and its interfaces with the flow channel and microporous layer or catalyst layer in polymer electrolyte fuel cells (PEFCs) play a significant role in water management and heat removal from the cells. Both surface morphology and surface wettability of GDL influence and control the water transport in PEFCs. Thus, the surface morphology and selectivity of its surface wettability are critical for PEFCs to provide optimum outputs. In this study, we have reported the fabrications of GDLs with a selective wetting pattern. Sigracet® GDLs were used as a substrate and two different monomers, polydimethylsiloxane (PDMS) added with fumed silica (Si) and fluorinated ethylene propylene (FEP) were used to print a selective pattern on the GDL surfaces. The evaluations of printed GDL surfaces, by means of static contact angle, sliding angles and scanning electron microscopy image, show that superhydrophobicity was achieved with both FEP and PDMS-Si coatings. Fourier Transform Infrared (FTIR) spectroscopy analysis confirmed the successful introduction of the functional groups in both the coatings. Finally, pore size distribution, sliding angle measurements and adhesion forces were used to investigate the interactions between the water droplets and GDL surfaces. The results of this study demonstrate that the present approach provides a novel but simple way to tune GDL surfaces with selective wetting properties and obtain superhydrophobic interfaces. The electrochemical results showed that an improvement can be achieved for the performance of PEFCs with patterned GDL/flow-channel interfaces.

An active carbon (AC)/AC electrochemical capacitor, taking advantage of a high-concentrated lithium trifluoromethane sulfonate (LiTFS) or lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) aqueous electrolyte, was demonstrated with an extended operating voltage of 2.5 V, which is the largest value till now for aqueous carbon-based capacitors. The AC electrode is entirely capacitive in these two electrolytes and the stable potential window of the single AC electrode can reach −1.2 to 1.2 V versus the saturated calomel electrode (SCE). The performance of the AC-based capacitor is evaluated in two- and three-electrode cells using a combination of electrochemical impedance (EIS), cyclic voltammetry (CV), galvanostatic discharge-charge, and self-discharge (SD, i.e., leakage current) measurements. At 0.5-mA cm −2 charge-discharge rate, the AC/AC capacitor presents 5.5 wh kg −1 and 4.5 wh kg −1 energy density for 20 m LiTFS and LiTFSI electrolyte, respectively. The results suggest that a thorough utilization of such lithium salt aqueous electrolytes with widening electrochemical stable potential window will no doubt lead to further development of electrochemical capacitors toward superior performance.

In this paper, we study, analyze, and validate some important zero-dimensional physics-based models for vanadium redox batch cell (VRBC) systems and formulate an adequate physics-based model that can predict the battery performance accurately. In the model formulation process, a systems approach to multiple parameters estimation has been conducted using VRBC systems at low C-rates (∼C/30). In this batch cell system, the effect of ions' crossover through the membrane is dominant, and therefore, the capacity loss phenomena can be explicitly observed. Paradoxically, this means that using the batch system might be a better approach for identifying a more suitable model describing the effect of ions transport. Next, we propose an efficient systems approach, which enables to help understand the battery performance quickly by estimating all parameters of the battery system. Finally, open source codes, executable files, and experimental data are provided to enable people's access to robust and accurate models and optimizers. In battery simulations, different models and optimizers describing the same systems produce different values of the estimated parameters. Providing an open access platform can accelerate the process to arrive at robust models and optimizers by continuous modification from the users' side.

The entire world is facing a great shortfall in the energy supply due to the high consumption rate of fossil fuel-based energy resources. Solid oxide fuel cells (SOFCs) are the best alternative energy devices, which convert hydrogen fuel directly into electricity. Alkali carbonated calcium-doped ceria electrolytes (LNK-CDC) as (Ce 0.8 Ca 0.2 ), (Ce 0.7 Ca 0.3 ), and (Ce 0.6 Ca 0.4 ) were synthesized by the co-precipitation method. With the addition of alkali carbonate, nanocomposites of ceria are well preserved after sintering at 600–700 °C. The structural and morphological properties were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Crystallite sizes were found in the range of 50–80 nm. The maximum ionic conductivity of LNK-CDC (Ce 0.8 Ca 0.2 ) was achieved to be 0.14 S/cm at 650 °C for anion vacancy migration by the dense microstructure. The minimum activation energy was determined to be 0.23 eV. The Fourier-transform infrared spectroscopy (FTIR) spectra of the prepared materials show the absorbance of IR and their behavior. The maximum power density of symmetric fuel cells LNK-CDC sandwiched with LNCZ oxide electrodes was recorded as 0.52 W cm −2 at 650 °C in the presence of hydrogen (fuel). It is suggested that coating of the equal molar ratio of ternary alkali metals on ceria doped comparatively enhance the performance of new nanocomposite electrolyte for SOFC and other energy applications.

Ferrous nitrate/nickel oxide {Fe(NO 3 ) 2 –NiO} nanocomposite was synthesized via two-step facile hydrothermal route. The nanocomposite exhibits crystalline structure as unveiled by X-ray diffraction (XRD) pattern, while as the scanning electron microscope (SEM) images divulge spherical morphologies for both Fe(NO 3 ) 2 as well as NiO nanoparticles differentiating from each other in size. Cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques were used to investigate supercapacitive behavior of the symmetrically fabricated nanocomposite electrode configuration using aqueous KOH as the electrolyte. The CV analyses demonstrate dominant electrical double layer capacitance (EDLC) behavior in the potential range of 0–1 V. From charge–discharge curves, the maximum specific capacitance calculated was 460 F g −1 corresponding to the energy density of 16 W h kg −1 at a high power density of 250 W kg −1 . EIS data affiliate well with the CV and GCD results justifying the maximum contribution of specific capacitance due to double layer capacitance. The nanocomposite retained 84% of its original capacitance after 1000 cycles and yielded maximum efficiency of 78%.

The chlor-alkali industry produces significant amounts of hydrogen as by-product which can potentially feed a polymeric electrolyte membrane (PEM) fuel cell (FC) unit, whose electricity and heat production can cover part of the chemical plant consumptions yielding remarkable energy and emission savings. This work presents the modeling, development, and experimental results of a large-scale (2 MW) PEM fuel cell power plant installed at the premises of a chlor-alkali industry. It is first discussed an overview of project’s membrane-electrode assembly and fuel cell development for long life stationary applications, focusing on the design-for-manufacture process and related high-volume manufacturing routes. The work then discusses the modeling of the power plant, including a specific lumped model predicting FC stack behavior as a function of inlet stream conditions and power set point, according to regressed polarization curves. Cells’ performance decay versus lifetime reflects long-term stack test data, aiming to evidence the impact on overall energy balances and efficiency of the progression of lifetime. Balance of plant is modeled to simulate auxiliary consumptions, pressure drops, and components’ operating conditions. The model allows studying different operational strategies that maintain the power production during lifetime, minimizing efficiency losses, as well as to investigate the optimized operating setpoint of the plant at full load and during part-load operation. The last section of the paper discusses the experimental results, through a complete analysis of the plant performance after startup, including energy and mass balances and allowing to validate the model. Cumulated indicators over the first two years of operations regarding energy production, hydrogen consumption, and efficiency are also discussed.

Multilayer nickel–copper coatings consisting of layers of nickel–copper alloy and a mixture of metals with hydroxides were obtained by electrodeposition from polyligand pyrophosphate–ammonia electrolyte by the two-pulse potentiostatic method. A comparison between two different electrodes with the same real surface area is presented. The equality of the surface area of electrodes deposited from the electrolyte containing different copper and nickel ions’ concentration ratio was achieved by deposition of different numbers of layers. It is shown that the increase in the copper content in electrolyte leads to an increase in the copper ions’ content in the coating and the electrode surface develops more intensively. Freshly deposited coatings have approximately the same catalytic activity in the glucose oxidation reaction in the alkaline solution. But a multilayer coating with a higher copper content is more corrosion resistant and more stable in long-term electrolysis.

A computational fluid dynamics model for high-temperature polymer electrolyte fuel cells (PEFC) is developed. This allows for three-dimensional (3D) transport-coupled calculations to be conducted. All major transport phenomena and electrochemical processes are taken into consideration. Verification of the present model is achieved by comparison with current density and oxygen concentration distributions along a one-dimensional (1D) channel. Validation is achieved by comparison with polarization curves from experimental data gathered in-house. Deviations between experimental and numerical results are minor. Internal transport phenomena are also analyzed. Local variations of current density from under channel regions and under rib regions are displayed, as are oxygen mole fractions. The serpentine gas channels contribute positively to gas redistribution in the gas diffusion layers (GDLs) and channels.

This paper describes electrocatalysts for the oxygen reduction reaction (ORR) in alkaline direct ethanol fuel cells (ADEFCs), using the non-noble metal electrocatalyst Ag/C, MnO 2 /C and AgMnO 2 /C. These electrocatalysts showed tolerance toward ethanol in alkaline media and therefore resistance to ethanol crossover in ADEFCs. Transmission electron microscopy, X-ray spectroscopy (EDX), cyclic voltammetry, and rotating disk electrode (RDE) were employed to determine the morphology, composition, and electrochemical activity of the catalysts. The herein presented results confirm that the AgMnO 2 /C electrocatalyst significantly outperforms the state-of-the art ORR catalyst platinum.

A thin and mechanically stable solid electrolyte interphase (SEI) is desirable for a stable cyclic performance in a lithium ion battery. For the electrodes that undergo a large volume expansion, such as Si, Ge, and Sn, the presence of a robust SEI layer can improve the capacity retention. In this work, the role of solvent choice on the electrochemical performance of Ge electrode is presented by a systematic comparison of the SEI layers in ethylene carbonate (EC)-based and fluoroethylene carbonate (FEC)-based electrolytes. The results show that the presence of FEC as a cosolvent in a binary or ternary solvent electrolyte results in an excellent capacity retention of ∼85% after 200 cycles at the current density of 500 mA g−1; while EC-based electrode suffers a rapid capacity degradation with a capacity retention of just 17% at the end of 200 cycles. Post analysis by an extensive use of X-ray photoelectron spectroscopy (XPS) was carried out, which showed that the presence of Li 2 O in FEC-based SEIs was the origin for the improved electrochemical performance.

Heat is a by-product of all energy conversion mechanisms. Efforts to utilize and dissipate heat remain a challenge for further development and optimization of energy conversion devices. Stationary thermo-electrochemical cell is a low cost method to harvest heat; however, it suffers from low power density. Flow thermo-electrochemical cell (fTEC) heat sink presents itself as a unique solution as it can simultaneously scavenge and remove heat to maintain devices in the operating range. In this work, multiwalled nanotube (MWNT) electrodes have been used and electrode configuration has been changed to maximize the temperature difference over a small interelectrode separation. As a result, power per unit area of fTEC heat sink has been improved by more than seven-fold to 0.36 W/m 2 .

Limited lifetime and performance degradation in lithium ion batteries in electrical vehicles and power tools is still a challenging obstacle which results from various interrelated processes, especially under specific conditions such as higher discharging rates (C-rates) and longer cycles. To elucidate these problems, it is very important to analyze electrochemical degradation from a mechanical stress point of view. Specifically, the goal of this study is to investigate diffusion-induced stresses and electrochemical degradation in three-dimensional (3D) reconstructed LiFePO 4 . We generate a reconstructed microstructure by using a stack of focused ion beam-scanning electron microscopy (FIB/SEM) images combined with an electrolyte domain. Our previous two-dimensional (2D) finite element model is further improved to a 3D multiphysics one, which incorporates both electrochemical and mechanical analyses. From our electrochemistry model, we observe 95.6% and 88.3% capacity fade at 1.2 C and 2 C, respectively. To investigate this electrochemical degradation, we present concentration distributions and von Mises stress distributions across the cathode with respect to the depth of discharge (DoD). Moreover, electrochemical degradation factors such as total polarization and over-potential are also investigated under different C-rates. Further, higher total polarization is observed at the end of discharging, as well as at the early stage of discharging. It is also confirmed that lithium intercalation at the electrode-electrolyte interface causes higher over-potential at specific DoDs. At the region near the separator, a higher concentration gradient and over-potential are observed. We note that higher over-potential occurs on the surface of electrode, and the resulting concentration gradient and mechanical stresses are observed in the same regions. Furthermore, mechanical stress variations under different C-rates are quantified during the discharging process. With these coupled mechanical and electrochemical analyses, the results of this study may be helpful for detecting particle crack initiation.

Three types of LiMn 2 O 4 (LMO) microspheres with different pore size are prepared by a facile method, using porous MnCO 3 –MnO 2 and Mn 2 O 3 microspheres as the self-supporting template, for lithium ion batteries (LIBs) cathode material. Briefly, Mn 2 O 3 and MnO 2 microspheres are heated in air at 600 °C for 10 h to synthesize porous Mn 2 O 3 spheres. Then the mixture of as-prepared spherical Mn 2 O 3 and LiNO 3 is calcined to obtain the LMOs. The morphology and structure of LMOs are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and nitrogen adsorption/desorption analyses. The result shows that the maximum pore diameters of LMOs are 17 nm, 19 nm, and 11 nm, respectively. All LMOs microspheres are composed of similar sized nanoparticles; however, the surface of these microspheres is strewed with dense tinier pores or sparse larger pores. Generally, the nanoparticles will reduce the path of Li + ion diffusion and increases the reaction sites for lithium insertion/extraction. Moreover, the pores can provide buffer spaces for the volume changes during charge–discharge process. The electrochemical performances of LMOs are investigated and LMO2 exhibits extremely good electrochemical behavior, especially the rate capability. The as-prepared LMO2 delivers a discharge capacity of 124.3 mAh g −1 at 0.5 C, retaining 79.6 mAh g −1 even at 5 C. The LMO2 sample also shows good capacity retention of 96.9% after 100 cycles at 0.5 C.

In this study, a new type of redox flow battery (RFB) named “membrane-less hydrogen-iron RFB” was investigated for the first time. The membrane is a cell component dominating the cost of RFB, and iron is an abundant, inexpensive, and benign material, and thus, this iron RFB without the membrane is expected to provide a solution to the challenging issues of current battery systems such as high cost and safety concerns. The research focus in this study was placed on defining key design parameters to make this new system promising as an RFB. Crossing rate of reactants over carbon porous electrode (CPE) was controlled by modifying its pore structure with Teflon impregnation, and the effects of the Teflon on crossover, kinetic, Ohmic, and mass transfer was investigated by cell-based test and one-dimensional computational model. It was found that the cell performance (i.e., charge and discharge polarization) of the new membrane-less system was equivalent to that of the conventional membrane-system (i.e., RFB having a membrane). Especially, the Ohmic properties of the new system were constant and stable, while in the conventional membrane system, they were significantly varied and deteriorated as cell tests were continued, indicating that degradation or contamination of membrane affecting Ohmic properties could be mitigated effectively in the membrane-less system, which was found first in this research. The modeling analysis provided insight into the system, showing that the effect of reactant crossover on performance decay was not significant, and Teflon impregnation in the CPE caused significant kinetic and Ohmic losses by impeding ion transport and reactant access to reaction sites. From this study, it was found that the membrane-less H 2 -iron system is feasible and promising in resolving the challenge issues of the conventional systems. And the results of this study are expected to provide guidelines for research and development of flow battery systems without having a membrane.

A planar solid oxide fuel cell (SOFC) was fabricated using a commercial Ni/yttria-stabilized zirconia (YSZ) anode support, an YSZ/gadolinium-doped ceria (GDC) thin-film electrolyte, and a composite cathode of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 /Gd 0.1 Ce 0.9 O 1.95 (LSCF/GDC). A small, three-cell, SOFC stack is assembled using 10 cm × 10 cm single cells, metallic interconnects, and glass-based sealing. The stack performance was examined at various fuel flow rates of H 2 + N 2 and air at a fixed temperature of 750 °C. The three-cell stack with a crossflow design produced peak power density of 0.216 W/cm 2 or about 39 W total power at 750 °C.

Thermal runaway is a phenomenon that occurs due to self-sustaining reactions within batteries at elevated temperatures resulting in catastrophic failure. Here, the thermal runaway process is studied for a Li-ion and Na-ion pouch cells of similar energy density (10.5 Wh, 12 Wh, respectively) using accelerating rate calorimetry (ARC). Both cells were constructed with a z -fold configuration, with a standard shutdown separator in the Li-ion and a low-cost polypropylene (PP) separator in the Na-ion. Even with the shutdown separator, it is shown that the self-heating rate and rate of thermal runaway in Na-ion cells is significantly slower than that observed in Li-ion systems. The thermal runaway event initiates at a higher temperature in Na-ion cells. The effect of thermal runaway on the architecture of the cells is examined using X-ray microcomputed tomography, and scanning electron microscopy (SEM) is used to examine the failed electrodes of both cells. Finally, from examination of the respective electrodes, likely due to the carbonate solvent containing electrolyte, it is suggested that thermal runaway in Na-ion batteries (NIBs) occurs via a similar mechanism to that reported for Li-ion cells.

Membrane electrolyte assembly (MEA) aging is a major concern for deployed proton exchange membrane (PEM) fuel cell stacks. Studies have shown that working conditions, such as the operating temperature, humidity, and open circuit voltage (OCV), have a major effect on degradation rates and also vary significantly from cell to cell. Individual cell health estimations would be very beneficial to maintenance and control schemes. Ideally, estimations would occur in response to the applied load to avoid service interruptions. To this end, this paper presents the use of an extended Kalman filter (EKF) to estimate the effective membrane surface area (EMSA) of each cell using cell voltage measurements taken during operation. The EKF method has a low computational cost and can be applied in real time to estimate the EMSA of each cell in the stack. This yields quantifiable data regarding cell degradation. The EKF algorithm was applied to experimental data taken on a 23-cell stack. The load profiles for the experiments were based on the FTP-75 and highway fuel economy test (HWFET) standard drive cycle tests to test the ability of the algorithm to perform in realistic load scenarios. To confirm the results of the EKF method, low performing cells and an additional “healthy” cell were selected for scanning electron microscope (SEM) analysis. The images taken of the cells confirm that the EKF accurately identified problematic cells in the stack. The results of this study could be used to formulate online sate of health estimators for each cell in the stack that can operate during normal operation.

Organic/inorganic materials are investigated as additives to improve the stability of a vanadium electrolyte for a vanadium redox flow battery (VRFB) at operating temperatures of 25 °C and 40 °C. Among these materials, the most effective additive is chosen based on the thermal stability and electrochemical performance with a long inhibition time. Through precipitation time and electrochemical measurements, the results show that the best inhibition effect is achieved by adding sodium pyrophosphate dibasic (SPD, H 2 Na 2 O 7 P 2 ) as an additive at a considerably high H 2 SO 4 concentration (3M) electrolyte, indicating an improved redox reversibility and electrochemical activity. Nonflow cell assembled with the SPD additive exhibits larger discharge capacity retentions of 40% than a blank solution with the retentions of 2% at 600 cycles at 40 °C. In the case of flow cell, the capacity retention on the SPD additive shows 55.4%, which is 5.3% higher than the blank solution at 40 °C and 180 cycles. The morphology of the precipitation is investigated by SEM, which exhibits more severe V 2 O 5 precipitation amount on the carbon felt electrode used in the blank electrolyte at 40 °C, which causes larger capacity losses compared to cells assembled with the SPD additive electrolyte.

The shuttle effect and poor conductivity of the discharge products are among the primary impediments and scientific challenges for lithium–sulfur batteries. The lithium–sulfur battery is a complex energy storage system, which involves multistep electrochemical reactions, insoluble polysulfide precipitation in the cathode, soluble polysulfide transport, and self-discharge caused by chemical reactions between polysulfides and Li metal anode. These phenomena happen at different length and time-scales and are difficult to be entirely gauged by experimental techniques. In this paper, we reviewed the multiscale modeling studies on lithium–sulfur batteries: (1) the atomistic simulations were employed to seek alternative materials for mitigating the shuttle effect; (2) the growth kinetics of Li 2 S film and corresponding surface passivation were investigated by the interfacial model based on findings from atomistic simulations; (3) the nature of Li 2 S 2 , which is the only solid intermediate product, was revealed by the density functional theory simulation; and (4) macroscale models were developed to analyze the effect of reaction kinetics, sulfur loading, and transport properties on the cell performance. The challenge for the multiscale modeling approach is translating the microscopic information from atomistic simulations and interfacial model into the meso-/macroscale model for accurately predicting the cell performance.

Ionic liquids are considered promising electrolytes for developing electric double-layer capacitors (EDLCs) with high energy density. To identify optimal operating conditions, we performed molecular dynamics simulations of N-methyl-N-propyl pyrrolidinium bis(trifluoromethanesulfonyl)imide (mppy + TFSI − ) ionic liquid confined in the interstices of vertically aligned carbon nanostructures mimicking the electrode structure. We modeled various surface charge densities as well as varied the distance between nanotubes in the array. Our results indicate that high-density ion storage occurs within the noninteracting double-layer region formed in the nanoconfined domain between charged nanotubes. We determined the specific arrangement of these ions relative to the nanotube surface and related the layered configuration to the molecular structure of the ions. The pitch distance of the nanotube array that enables optimal mppy + TFSI − storage and enhanced capacitance is determined to be 16 Å.