Single Cell Test Research Articles

Dual-porous structured membrane for ion-selection in vanadium flow battery

Porous membranes based on low-cost, chemically robust and non-ionic polymers are found to be promising as ion-selective membranes in redox flow batteries. Herein, we fabricate a dual-porous structured membrane where micro and macro pores are formed in the Nafion/poly(vinylidene fluoride) hybrid matrix. The dual-porous structure of the membranes is constructed by using polyethylene glycol as a pore-forming template. It is revealed that Nafion resin has significant impacts on both pore formation and ion conduction. The proton conductivity of the dual-porous membrane reaches 49.1 mS cm−1, and its vanadium permeation can be notably suppressed. Result of the single cell test indicates that, with the dual-porous structured membrane, coulombic efficiency and energy efficiency of the cells can achieve 96.1% and 83.8%, respectively, at 100 mA cm−2. The characteristics of low cost (approximately 50% of the material cost of Nafion), suppressed vanadium permeation, good chemical stability and competitive electrochemical performance make the dual-porous blend membranes promising candidate for redox flow batteries.

Effect of heat treatment on the surface structure of Pd@Pt–Ni core-shell catalysts for the oxygen reduction reaction

To promote the commercialization of fuel cells by reducing cost, it is essential to reduce the amount of Pt in the catalyst and apply the low-Pt catalysts to the membrane electrode assembly (MEA). In this work, the high-performance Pd@Pt-Ni/C catalysts are prepared by a simple and effective method and applied in MEAs successfully. The particle size of the core-shell structure catalyst (Pd@Pt–Ni/C-200 °C) is around 4.5 nm and the particles are evenly dispersed on the carbon support. By optimizing the heat treatment temperature, it is found that the reduction of Pt on the surface of the catalyst can be achieved and the uniform distribution of the Pt-Ni shell can also be promoted to enhance the catalyst activity at 200 °C. Besides, the heat treatment at 200 °C can not only extend the stability of the catalyst but also avoid excessive particle size growth. The mass activity (MA) is nearly 5.1 times higher than that of commercial Pt/C catalysts (JM). After the accelerated degradation testing (ADT), the half-wave potential of Pd@Pt–Ni/C-200 °C only shifted 6 mV and MA could maintain 85.5%. In single-cell tests, the MEA prepared by Pd@Pt-Ni/C-200 °C has a maximum power density of 0.92 W/cm2, which is 2.2% higher than that of Pt/C. Besides, the oxygen mass transfer resistance of MEA-Pd@Pt-Ni/C (23.0 s/m) is lower than that of MEA-Pt/C (26.2 s/m), indicating that the catalyst layer prepared by Pd@Pt–Ni/C is more conducive to oxygen transmission. It indicates that the Pd@Pt-Ni/C core-shell catalyst can be the promising catalyst to be applied to proton exchange membrane fuel cells (PEMFC).

An All-Aqueous Thermally Regenerative Ammonia Battery Chemistry Using Cu(I, II) Redox Reactions

Thermally regenerative ammonia batteries (TRABs) are electrochemical energy conversion devices that convert low-grade waste heat into electrical power. To date, reported TRABs have suffered from poor performance due to their reliance on dissolution and deposition redox reactions with transition metals. Here we present a new TRAB chemistry that uses ligands to stabilize aqueous Cu(I) and Cu(II) ions, thereby creating the first reported all-aqueous TRAB. Rotating disc electrode studies were conducted to evaluate thermodynamic and kinetic parameters of prospective anolyte and catholyte chemistries. The use of NH3(aq) and Br−(aq) ligands resulted in a cell potential difference of 695 ± 2 mV with rate constants of 101 ± 5 μm s−1 and 819 ± 236 μm s−1, respectively. Single-cell tests achieved power densities up to 350 W m−2 which are the highest reported for single metal TRABs at 25 °C. Coulombic efficiencies exceeded 90% and their energy storage densities were two to four times of those reported for alternative TRAB chemistries.

V2O5-Activated Graphite Felt with Enhanced Activity for Vanadium Redox Flow Battery

In this study, a simple and environment-friendly method of preparing activated graphite felt (GF) for a vanadium redox flow battery (VRFB) by depositing the vanadium precursor on the GF surface and calcining vanadium oxide was explored. The intermediate material, VO2, generated carbon oxidation during the calcination. In contrast to the normal etching method, this method was simple and without a pickling process. On the surface of the activated GF, multiple pores and increased roughness were noted after the calcination temperature and surface area of the activated GF reached 350 °C to 400 °C and 17.11 m2/g, respectively. Additionally, the polarization of the activated GF decreased with resistance to the charge transfer at 0.27 Ω. After a single-cell test at current density of 150 mA/cm2 was performed, the capacity utilization and the capacity retention after 50 cycles reached 70% and 84%, respectively. These results indicated the potential use of activated GF as an VRFB electrode.

Fast Antibiotic Susceptibility Testing via Raman Microspectrometry on Single Bacteria: An MRSA Case Study.

Despite recent advances in molecular diagnostics, ultrafast determination of the antibiotic susceptibility phenotype of pathogenic microorganisms is still a major challenge of in vitro diagnostics (IVD) of infectious diseases. Raman microspectroscopy has been proposed as a means to achieve this goal. Previous studies have shown that susceptibility phenotyping could be done through Raman analysis of microbial cells, either in large clusters or down to the single-cell level in the case of Gram-negative rods. Gram-positive cocci such as Staphylococcus aureus pose several challenges due to their size and their different metabolic and chemical characteristics. Using a tailored automated single-cell Raman spectrometer and a previously proposed sample preparation protocol, we acquired and analyzed 9429 S. aureus single cells belonging to three cefoxitin-resistant strains and two susceptible strains during their incubation in the presence of various concentrations of cefoxitin. We observed an effect on S. aureus spectra that is weaker than what was detected on previous bacteria/drug combinations, with a higher cell-to-cell response variability and an important impact of incubation conditions on the phenotypic resistance of a given strain. Overall, the proposed protocol was able to correlate strains’ phenotype with a specific modification of the spectra using majority votes. We, hence, confirm that our previous results on single-cell Raman antibiotic susceptibility testing can be extended to the S. aureus case and further clarify potential limitations and development requirements of this approach in the move toward industrial applications.

Experimental and Modeling Investigation of CO3=/OH– Equilibrium Effects on Molten Carbonate Fuel Cell Performance in Carbon Capture Applications

Molten Carbonate Fuel Cells (MCFCs) are used today commercially for power production. More recently they have also been considered for carbon capture from industrial and power generation CO2 sources. In this newer application context, our recent studies have shown that at low CO2/H2O cathode gas ratios, water supplements CO2 in the electrochemical process to generate power but not capture CO2. We now report the direct Raman observation of the underlying carbonate-hydroxide equilibrium in an alkali carbonate eutectic near MCFC operating conditions. Our improved electrochemical model built on the experimental equilibrium data adjusts the internal resistance terms and has improved the representation of the MCFC performance. This fundamentally improved model now also includes the temperature dependence of cell performance. It has been validated on experimental data collected in single cell tests. The average error in the simulated voltage is less than 4% even when extreme operating conditions of low CO2 concentration and high current density data are included. With the improvements, this electrochemical model is suitable for simulating industrial cells and stacks employed in a wide variety of carbon capture applications.

Sulfonated tryptanthrin anolyte increases performance in pH neutral aqueous redox flow batteries

Aqueous organic redox flow batteries (AORFBs) hold great promise as low-cost, environmentally friendly and safe alternative energy storage media. Here we present aqueous organometallic and all-organic active materials for RFBs with a water-soluble active material, sulfonated tryptanthrin (TRYP-SO3H), working at a neutral pH and showing long-term stability. Electrochemical measurements show that TRYP-SO3H displays reversible peaks at neutral pH values, allowing its use as an anolyte combined with potassium ferrocyanide or 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt monohydrate as catholytes. Single cell tests show reproducible charge-discharge cycles for both catholytes, with significantly improved results for the aqueous all-organic RFB reaching high cell voltage (0.94 V) and high energy efficiencies, stabilized during at least 50 working cycles.

Boosting the Role of Ir in Alleviating Corrosion of Carbon Support By Alloying with Pt

The degradation of PEMFC is a very complex phenomenon and is affected by various factors. Among the components of PEMFC, an electrode composed of a carbon-supported platinum nanoparticle catalyst (Pt/C) plays an important role in determining the durability of PEMFC. Typically, PEMFCs have an operating voltage range of 0.5–1.0V. During long-term operation under these conditions, Pt nanoparticles agglomerate, reducing the active surface area and gradually reducing electrode performance. On the other hand, abnormal conditions such as low fuel and start/shutdown (SU/SD) cycles produce abnormally high potentials above 1.4V at the electrodes. At this high potential, the carbon support corrodes to form carbon dioxide (C + 2H2O → CO2 + 4H + + 4e–, E0 = 0.207 V), leading to loss of supported Pt nanoparticles and rapid decay or catastrophic failure of electrode performance. Automotive PEMFCs, which are more often exposed to the aforementioned abnormal conditions, have a shorter life (almost thousands of hours) than stationary PEMFCs (nearly tens of thousands of hours). This clearly means that these dynamic conditions will decisively affect the degradation of PEMFC.Extensive research efforts have been made to mitigate the corrosion of carbon supports to improve the durability of PEMFC. First, it improves the corrosion resistance of these materials by modifying the surface properties and crystallinity of carbon. Second, corrosion-resistant and electrically conductive oxides and transition metal carbides have been explored as alternative supports for Pt nanoparticles to remove carbon from the electrode. Electrodes without supports, such as nanostructured thin film electrodes, have also been proposed to remove carbon from the electrode. On the other hand, operating procedures or plant balances (BOPs) have been developed to avoid exposure to cell reversal or reverse current conditions. Despite these studies, the lifetime of automotive PEMFCs is limited due to carbon corrosion, but this is not the only issue. Nevertheless, the mitigation of carbon corrosion remains an important challenge.With a new approach, iridium oxide (IrO2) is incorporated into the Pt/C electrode as an additive that protects carbon from corrosion with the help of sacrificial oxidation of water (or oxygen evolution reaction, OER) demonstrating improved durability in both half-cell and single-cell tests. However, the function of the OER catalyst was not clear in terms of composition and distribution, which is a prerequisite for further improvement of cathode durability. This study aims to gain a mechanical understanding of OER functional Ir-containing Pt/C electrodes. Carbon-supported Pt–Ir alloy catalysts (PtxIry/C) are synthesized in various compositions and are exposed to potential cycles from 1.0 to 1.5 VRHE compared to Pt/C and mixtures of Pt/C and Ir/C (Pt/C + Ir/C, Pt-Ir ratio 85:15). Pt85Ir15/C has been proven to be more resistant to carbon corrosion than Pt/C as well as Pt/C+Ir/C due to Ir atomically distributed in Pt85Ir15/C. The corrosion behavior of the carbon support is thoroughly investigated by the identical location transmission electron microscopy (IL-TEM), differential electrochemical mass spectrometry (DEMS), and X-ray photoelectron spectroscopy (XPS). As a cathode catalyst, Pt85Ir15/C exhibits much higher oxygen reduction reaction (ORR) activity than Pt/C after potential cycles, which is associated with the formation of high-index facets of Pt as revealed by high-resolution TEM (HR-TEM) and inductively coupled plasma mass spectrometry connected to a scanning flow cell (SFC/ICP-MS). This study suggests that the atomic-level distribution of Ir is a key factor in effectively mitigating carbon corrosion and improving PEMFC durability.

Ru2P nanofibers for high-performance anion exchange membrane water electrolyzer

The development of advanced electrodes with highly active electrocatalysts and appropriate structures is essential for sustainable hydrogen production via water electrolysis. Moreover, there is significant demand for an affordable electrocatalyst that exhibits comparable activity to that of Pt. Herein, we report Ru2P nanofibers (NFs) as an efficient electrode material for a high-performance anion exchange membrane water electrolyzer (AEMWE). The electrospinning method enables the formation of a porous catalyst layer that comprises tangled NFs, which exhibit a three-dimensional structure with abundant empty space. In a half cell test, the Ru2P NFs exhibit a high catalytic activity for the hydrogen evolution reaction, which is comparable to the activity of a commercial Pt/C. In a single cell test, an AEMWE with Ru2P NFs demonstrates a higher performance than that with a commercial Pt/C, especially in the high current density region; this is attributed to the structural advantage of the porous catalyst layer, which enhances the mass transfer of the reactant, as well as the product.

Experimental investigation of the influence of electrical contact resistance on lithium-ion battery testing for fast-charge applications

With the rising demand for electric vehicles with a fast-charging ability, high currents are applied to lithium-ion batteries to develop accurate battery models and intelligent fast-charging strategies. In order to achieve reliable results for automotive applications, single cell test conditions should be as close as possible to the conditions present in the battery pack of the battery electric vehicle. As cells are irreversibly connected in a battery pack, electrical contact resistance (ECR) is usually in the magnitude of <1 mΩ, and thus far lower than in reversible contacts during lab-testing. An interesting question arises as to whether this ECR has any unintended influence on the battery cell during testing. In this article, various experiments with high charge rates of up to 5C are performed in order to assess the impact of the ECR of the measurement setup on the cells’ behavior. Two different commercial contact probes with different ECRs are tested on a 18650 lithium-ion battery, and compared to a laser-welded cell as a benchmark. ECRs of the lab-testing setups are measured with a micro ohmmeter, and the temperature evolution of all cells studied is measured at both cell tabs and the cell mantle during cycling. The results show that high peak temperature differences due to parasitic joule heat at the lithium-ion battery tabs occur when applying full charge cycles from 0.5C to 5C. Repetitive cycling with a multistage fast-charging strategy indicates a correlation of ECR with peak temperatures and aging spread. As a consequence, high ECRs could negatively affect drawn conclusions of cycle life tests. They should therefore be taken into account and kept low in any examination of fast-charging strategies.

High-Performance Ru 2 P Anodic Catalyst for Alkaline Polymer Electrolyte Fuel Cells

High-Performance Ru ₂ P Anodic Catalyst for Alkaline Polymer Electrolyte Fuel Cells

A novel multi-physics and multi-dimensional model for solid oxide fuel cell stacks based on alternative mapping of BP neural networks

Solid oxide fuel cell (SOFC) stacks have complex multi-physics and multi-dimensional properties that are very difficult to observe in experiments. To solve this problem, a new modeling concept called alternative mapping is introduced in this paper. Using an artificial neural network (ANN), a multi-physics and multi-dimensional stack model can be decomposed into two bonded layers. Both can be solved much more rapidly and robustly than conventional models without losses in accuracy. A SOFC stack model is developed based on this concept. It is calibrated and validated by data from a single cell test and 30-layer stack experiments. The model is robust and rapid. The stack model results show that different physics and dimensional properties are closely related. Changes in each may cause chain reactions in the others, influencing the electrical efficiency or operation ranges. In this report, a fully 3D multi-physics and multi-dimensional dynamic simulation of a SOFC stack is implemented for the first time. Its dynamic behavior is a composite of electric-chemical reactions, gas transport, and heat transfer. These factors vary considerably in different positions and operational conditions.

Microstructure and electrochemical behavior of layered cathodes for molten carbonate fuel cell

In the present paper, we demonstrate how modifications of the microstructure and the chemical composition can influence the electrochemical behavior of cathodes for molten carbonate fuel cells (MCFCs). Based on our experience, we designed new MCFC cathode microstructures combining layers made of porous silver, nickel oxide or nickel foam to overcome common issues with the internal resistance of the cell. The microstructures of the standard NiO cathode and manufactured cathodes were extensively investigated using scanning electron microscopy (SEM) and porosity measurements. The electrochemical behavior and overall cell performance were examined by means of electrochemical impedance spectroscopy and single-cell tests in operation conditions. The results show that a porous silver layer tape cast onto standard NiO cathode and nickel foam used as a support layer for tape cast NiO porous layer substantially decrease resistance components representing charge transfer and mass transport phenomena, respectively. Therefore, it is beneficial to combine them into a three-layer cathode since it facilitates separation of predominant physio-chemical processes of gas and ions transport in respective layers ensuring high efficiency. The superiority of the three-layer cathode has been proven by low impedance and high power density as compared to standard NiO cathode.

On the path to aqueous organic redox flow batteries: Alizarin red S alkaline negolyte. Performance evaluation and photochemical studies

An aqueous organic redox flow battery (AORFB) based on Alizarin Red S, 3,4-dihydroxy-9,10-anthraquinone-2-sulfonic acid (ARS) and potassium ferrocyanide (PF) was studied in alkaline medium. Charge-discharge processes and potential-current response behaviour in a full cell combining ARS, as the negolyte, and PF, as the posolyte, were investigated. The diffusion coefficient (D) and kinetic rate constant (k0) of ARS were obtained from electrochemical measurements indicating a two-electron reduction reaction of ARS. The electrochemical stability test of the redox pair showed that the negolyte (ARS), even when subjected to extreme potential and current conditions, does not lose its redox activity and exhibits good performance without significant losses of efficiencies in a single cell test. The AORFB was found stable with an average storage capacity of 5.9 mWh L-1 and capacity retention of 89 and 91.5% for a single cell test before and after stability test, respectively. Additionally, the photophysics of ARS was investigated aiming to rationalize the stability of the compound as negolyte. The system showed to have potential as an organic aqueous flow battery closely related to the electrochemical stability and efficiencies associated to ARS.

Directly sputtered nickel electrodes for alkaline water electrolysis

Hydrogen is regarded as a highly clean and renewable future energy resource. Water electrolysis (WE) is the most promising technology to produce hydrogen at large scale without carbon dioxide generation. In this study, we prepared Ni electrodes for alkaline water electrolysis purpose using various methods, including direct sputtering (DC and RF operational modes) and the Raney Ni process, and investigated their morphologies and electrochemical activities in the hydrogen evolution reaction (HER). The DC-sputtered Ni electrode showed well-controlled surface morphology with around 40-fold roughness enhancement, compared to the Ni substrate. Half-cell HER test showed that DC-sputtered Ni electrode provides the best electrochemical performance, including the lowest overpotential of 100 mV at a current density of 50 mA/cm2, and provides the lowest Tafel slope, representing the fastest charge transfer reaction and kinetics of HER. More importantly, for practical application purposes, single-cell test was also conducted to confirm the on/off durability and long-term stability, which showed highly stable electrochemical activity under harsh operational conditions. We expect that our approach will launch a new trajectory for realizing CO2-free, cost-effective, and scalable hydrogen production for industrial application purpose, even in combination with renewable power sources, including solar, wind, and hydro energy.

An overview of safety for laboratory testing of lithium-ion batteries

Secondary Lithium-ion batteries are widely used in a variety of sizes from single cells in personal electronics, to large packs in Electric Vehicles (EVs), and very large packs in grid-scale storage. With the number of applications increasing, this brings more laboratory testing of such batteries. A number of papers discuss the safety intrinsic to cells, however, excluding EVs there is little discussion of cycling larger, multi-cell packs. This paper considers safe laboratory testing of commercial high capacity single cells and multi-cell battery packs. Using the hazards and failure modes that can occur, appropriate control measures are proposed, including fuses, contactors and good practice in system design. Suitable enclosures and fire suppression are also recommended should these measures fail. For single cells without a BMS, a separate protection circuit is presented utilizing analogue components for reliability.

High performance and cost-effective supported IrOx catalyst for proton exchange membrane water electrolysis

A multistep synthesis method is introduced to fabricate high performance IrOx/W-TiO2 catalyst for noble metal reduction in PEM water electrolyzers. The performances of the IrOx/W-TiO2 catalyst for oxygen evolution reaction (OER) are measured in half-cells and single-cells and compared with unsupported IrOx and commercial IrO2. In half-cell tests, IrOx/W-TiO2 displays an improved Ir mass activity compared with the unsupported IrOx, demonstrating a positive effect of the support material. In single-cell tests, the performance of IrOx/W-TiO2 also exceeds both the unsupported and commercial IrO2. The cell voltage reaches 1.602V at 1 A cm−2 (Nafion 212) with total noble metal loading less than 0.2 mg cm−2, suggesting that significant Ir reductions are possible by using IrOx/W-TiO2 without sacrificing the cell performance. It also shows improved durability than other unsupported catalysts at reduced Ir loading. In-situ electrochemical test reveals that the performance is associated with the enhanced conductivity of the catalyst layer.

The Development of a Highly Durable Fe-N-C Electrocatalyst With Favorable Carbon Nanotube Structures for the Oxygen Reduction in PEMFCs

Abstract Proton exchange membrane fuel cell (PEMFC) is a crucial route for energy saving, emission reduction, and the development of new energy vehicles because of its high power density, high energy density, as well as the low operating temperature which corresponds to fast starting and power matching. However, the rare and expensive Pt resource greatly hinders the mass production of the fuel cell, and the development of highly active and durable non-precious metal catalysts toward the oxygen reduction reaction (ORR) in the cathode is considered to be the ultimate solution. In this article, a highly active and durable Fe-N-C catalyst was facilely derived from metal-organic framework (MOF) materials, and a favorable structure of carbon nanotubes (CNTs) was formed, which accounts for a desired good durability. The as-optimized catalyst has a half-wave potential of 0.84 V for the ORR, which is comparable to that of commercial Pt/C. More attractively, it has good stabilities both in rotating disk electrode (RDE) and single-cell tests, which provides a large practical application potential in the replacement of Pt catalyst as the ORR electrocatalyst in fuel cells.

Geometry-Induced Asymmetric Vanadium-Ion Permeation of PVDF Membranes and Its Effect on the Performance of Vanadium Redox Flow Batteries

In vanadium redox flow batteries (VRFBs), size-exclusive porous separators are of great interest as alternative membranes to the conventional ion-exchange membranes. In this study, we have shown geometry-induced asymmetric vanadium permeation through porous poly(vinylidene fluoride) (PVDF) membranes having asymmetric pore structures. The asymmetric pore geometry was developed via non-solvent-induced phase separation (NIPS) of the PVDF/N,N-dimethylacetamide film in water at various coagulation bath temperatures (30–70 °C). The membranes show two distinct regions across their thickness direction, finger-like and sponge-like structures near the top and bottom of the membranes. In the permeability experiments, vanadium-ion (VO2+) permeability through a fixed asymmetric membrane was significantly affected by the direction of the VO2+ concentration gradient. The vanadium-ion permeation was higher when the finger-like top layer of the membrane faced the vanadium-ion solution than the other direction, while proton permeation was almost identical regardless of the direction. In single-cell tests, this geometry-induced asymmetric ion selectivity resulted in different performances depending on the direction of the membranes; VRFBs performed better when the sponge-like bottom layer faces the anolyte side, which contains more permeable vanadium ions (VO2+, VO2+) through porous membranes than other ions (V2+, V3+).

Assist more Pt-O bonds of Pt/MoO3-CNT as a highly efficient and stable electrocatalyst for methanol oxidation and oxygen reduction reaction

Pt-based catalysts are widely used in polymer electrolyte fuel cells. However, it still exists tremendous challenge on improving the activity and durability of electrocatalysts. Herein, Pt nanoparticles (NPs) are supported on the dispersed MoO3-modified carbon nanotubes (CNTs) via an atomic layer deposition (ALD) technology. In the resulting Pt-MoO3/CNT-ALD, Pt NPs are selectively anchored on the interface of MoO3 and CNTs to increase the Pt-O bonds and strengthen the metal-metal oxide interaction (MMOI). The regulated electronic structure of Pt can remarkably enhance the intrinsic catalytic activity. For methanol oxidation reaction, Pt-MoO3/CNT-ALD exhibits high activity with a mass activity of 1221.1 mA·mgPt−1 at 0.9 V which represents a 4.2-fold improvement over the corresponding activities of commercial Pt/C. And for oxygen reduction reaction, it shows the onset potential and half potential of 1.04 V and 0.87 V, respectively. Most importantly, Pt-MoO3/CNT-ALD exhibits excellent long-term stability without distinct degradation (98.9% retention of electrochemical surface area and 92.4% retention of mass activity) after 10,000 cycles. In single cell test, the maximum power density and durability of the Pt-MoO3/CNT-ALD is achieved to be 589 mW·cm−2 and 94.8% retention after 3000 cycles. The Pt-MoO3/CNT-ALD with high activity and durability is attributed to the increased Pt-O bonds, optimized electronic structure and strengthened MMOI. A strategy in this work is approved to facilitate the development of high-performance Pt-based electrocatalysts.