Electrochemical Phenomena Research Articles

Electrochemical Phosphorous Recovery from Wastewater: Modeling & Scale-up Considerations

The prospect of electrifying the recovery of valuable nutrients from waste streams is of great interest in the effort of reducing the overall energy consumption and environmental impact of nutrient usage. Currently, many electrochemical precipitation technologies exist, and some have shown energy consumption values on par with implemented nutrient recovery technologies (both gravimetric for specified products and volumetric for waste stream handling). However, electrochemical precipitation technologies are at low-to-intermediate Technology Readiness Levels (TRLs) and need to be optimized and scaled to determine the feasibility of implementing them industrially. This presentation discusses necessary considerations for modeling and scaling electrochemical precipitation technologies from the perspective of phosphorus (P) recovery.Two specific modeling tools were used to study P recovery as struvite. Mass transport and electrochemical phenomenon were modeled using COMSOL within a stirred batch reactor format. The COMSOL modelling yields valuable information about limiting conditions, spatial distribution of dissolved species concentrations, and the effects of various reactor conditions (e.g., stirring or applied potential). Next, the precipitation of struvite under various solution conditions is discussed with respect to a thermodynamic model of precipitation developed using OLI Flowsheets. The precipitation study is then discussed with respect to modeled reactor conditions to ascertain information relevant to scaling electrochemical P precipitation. Figures of Merit (FOM) useful in scaling electrochemical reactions are highlighted to alleviate the dependence on the reactor design used for modelling, enabling a transfer of information to other reactor formats.

Experimental and Numerical Study of Electrolyte Mixing in the Tanks of Vanadium Redox Flow Batteries: Insights from Conventional and 3D-Printed Tanks

Vanadium redox flow batteries (VRFBs) are a promising technology for large-scale grid energy storage. Despite extensive research on the electrochemical and fluid dynamic phenomena in the cells or stacks [1, 2], the impact of electrolyte flow and mixing in the tanks has received much less attention. Previous research has shown that the cell potential and battery capacity may substantially differ from those predicted under the perfect mixing assumption [3] (i.e., continuous stirred-tank reactor). Recent numerical simulations have detected the formation of segregated zones within the tanks that cause inhomogeneous electrolyte utilization and significant capacity decay [4]. The authors have confirmed these results by means of transient laminar numerical simulations [5] and experimental testing of an industrial VRFB system [6]. However, these first attempts should be carefully extended, using a well-controlled lab-scale system, so that the effects of the different components can be independently studied.In this study, we investigate the effect of electrolyte mixing on VRFB response using a medium-size lab-scale system. Two experimental campaigns were conducted to explore i) the impact of flow rate and applied current on the predicted fluid behavior, and ii) the performance of 3D-printed tanks designed for improving electrolyte mixing with reduced dead recirculation zones. In both campaigns, the transient response of the system was investigated to assess the effect of electrolyte mixing on battery performance. The experimental results were also compared with numerical simulations, which showed good agreement with the experimental data.This work makes a novel contribution to the field by using 3D-printed tanks to investigate the impact of electrolyte mixing on RFB performance. The results extend previous research on this topic and provide insights into the design of RFBs for improved energy storage. Specifically, the use of 3D-printed tanks could be a promising approach to address the issue of inhomogeneous electrolyte exploitation in RFBs. The findings of this study could serve in the design of RFBs for large-scale grid energy storage and facilitate the adoption of this technology as a sustainable energy storage solution.

(Invited) Gravitational Level Effects on Electrochemical Interfacial Phenomena

Electrochemical copper refining technology invented in Niagara area made a great progress over more than 100 years through better understanding of natural convection phenomena. Ionic mass-transfer rate enhanced by natural convection developing along 1m high vertical electrode surfaces has been unconsciously utilized by trial-and-error method. As the local electrolyte composition is partly stratified in an electrolytic cell (roughly 5m long x 1.3m wide x 1.3m depth). The industrial electrolytic tank house is composed of about 1000 cells through which the electrolyte is continuously supplied. Thus, the electrolyte circulation is a key technology in industrial copper refining processes as well as appropriate selection of effective additive and stable sedimentation of anode slime containing precious metals on the electrolytic tank bottom.On the other hand, Cu nanowire arrays were electrodeposited potentiostatically with PC filter template in two kinds of electrolytic cell configurations: cathode over anode (C/A) and anode over cathode (A/C). The effect of gravitational level on the coupling phenomena between the morphological variation and the ionic mass transfer rate in nanosized pores(a mesoscopic scale of a fewμm high and 30nm in diameter) was also found. Hitherto, the coupling phenomena accompanied with the electrochemical interfacial reactions confined in such a mesoscopic space has not been studies in spite of the great technological interest for the production of micro- or meso-scale fabrication techniques encountered in microelectronics and energy conversion & storage technology field. The initial stage including nucleation and growth process during electrochemical phase transformation reactions must be at first focused to profoundly comprehend the present subject in order to reasonably design such an advanced device technology.Fundamental aspects in electrochemical processes in microgravity environments have not been frequently reported. However, Artemis projects may provide the large opportunities on the energy storage and power generation, as well as materials processing. The effects of gravitational level and magnetic field gradient on the electrochemical interfacial phenomena should be understood. The drop tower facility surely offers the appropriate & “unique” experimental opportunities to propose such research program in the future space engineering fields. Electrocrystallization of metals is selected as a good subject for starting direction of research. Its reaction mechanism is relatively simple, the deposition rate can be easily varied by changing the current density or potential, and a smooth copper film is deposited so long as it is not too thick.By the way, the damascene process has been introduced to copper wiring process in ULSI field by IBM almost 25 years ago. It is important to control the nucleation and crystal growth in the initial stages of electrodeposition process. For this purpose, many effects of additive have been intensively examined. However, few quantitative examinations have been reported on the coupling phenomena of ionic mass transfer and nucleation and crystal growth. In the present work, we introduce various gravitational levels as new parameters into the nonequilibrium electrochemical processing in order to create or tailor the unique physical properties in nano space field. It is fruitful in terms of physicochemical hydrodynamics that the experiments are done under various gravitational levels. In fact, it has been confirmed that the gravitational levels as well as the magnetic field introduce the intensified effects from that under 1 G normal environment. Here is a report to analyze the effect of gravitational level on the initial stages of Cu electrodeposition on TaN or TiN substrate.

Identifying Thermal Decomposition Mechanisms of the Solid Electrolyte Interphase with in-Situ Gas Analysis of Lithium-Ion Batteries

The global shift away from fossil fuels has generated an unprecedented demand for electric vehicles and a steady increase in the prevalence of lithium-ion batteries. Additionally, increases in the energy density of storage technologies has led to a corresponding increase in safety concerns regarding thermal runaway reactions. The components of a lithium-ion battery can self-react when exposed to an external heat source, which can cause a thermal runaway reaction process and large-scale fires of the cell. The initial reactions in this process involve the decomposition of the Solid Electrolyte Interphase (SEI) breakdown and conductive salt. The underlaying mechanisms behind these reactions are unclear; in-depth investigations are needed in order to develop a detailed understanding of the thermal runaway process and guide the development of strategies to mitigate the safety hazards posed by these battery systems. In the past, differential/online electrochemical mass spectrometry (DEMS/OEMS) was utilized to analyze the buildup of the SEI as well as decomposition due to overcharge. Our new methodology of high temperature (HT-)OEMS, with a maximum temperature of 132 °C, can simulate heating events with thermal ramps on an in-situ test cell battery. These measurements reveal information regarding reaction product gases and cell voltage drop during first formation and thermal stress tests, and provide novel insight into the electrochemical and thermodynamic phenomena during thermal abuse of lithium-ion batteries.In this study, we use (HT-)OEMS to investigate the behavior of lithium-ion cells with varied additive concentrations and formation currents. This new methodology allowed us to clearly determine that both of the testing parameters impact the formation gas evolution and thus influence the SEI-composition. Systems with high formation rates, as well as with lower concentrations of additives, exhibited an increase in the fraction of CO product gases, which can be explained with a higher presence of lithium alkoxides in the SEI. Additionally, the evolution of H2, CO2 and POF3 gases were observed at temperatures around 80 °C for cells during the thermal stress test after formation. These results allow us to establish a correlation between the thermal conductive salt decomposition and the formation of the SEI-components Li2CO3 and (CH2OLi)2.The identification of the underlying degradation mechanisms and process correlations via (HT-)OEMS provides a novel and important understanding of the phenomena that give rise to thermal runaway in lithium-ion batteries. This cell chemistry-based insight can be used to guide future prevention-focused safety assessments. Figure 1

Study of Fuel Cell Stacks Combining Pseudo-3D Multi-Physics Simulations with Experimental Mappings of Current Density and Liquid Water

In this work, experimental and numerical analyses of Proton Exchange Membrane Fuel Cell stacks for automotive application are proposed. Performance and durability of PEMFC stacks strongly rely on an optimized water management. An adequate balance has to be found between a sufficient membrane hydration enhancing electrical conductivity and a limited liquid water presence avoiding water flooding. This requires investigations at a local scale inside the cells, because the location of water condensation is not distributed homogeneously in the active area, due to spatial variations of temperature, gas composition or current density.Allowing the quantification of liquid water locally inside PEMFCs, neutron imaging is a powerful tool for the analysis of fuel cell operation at a local scale. It is generally used with single cells and not with stacks, due to the complexity of such experiments. A quantification of liquid water over the active area is obtained through neutron imaging of stacks for several operating conditions. Specific segmented high surface sensors are placed inside stacks to map the current density and temperature distribution in the same area. A multi-physics pseudo-3D two-phase flow model coupling all the electrochemical and transport phenomena supports the understanding of the relationship between all these parameters. The comparison with experimental mappings validates the model, which is able to predict both the current density and the amount of liquid water at a local scale. Unlike experimental measurements that gives a total amount of liquid water in the cell, the model allows to distinguish between anode and cathode sides, or between channels and GDLs, providing crucial information regarding flooding phenomena. Moreover, the flowing direction of the fluids inside the stack have a major influence on liquid water distribution. As a general trend, it is observed that the average total water thickness always decreases when current density increases, in all tested stack flow configurations. Furthermore, a clear relationship appears between flooding, cathode pressure drop and cathode liquid water content. Finally, a detailed analysis is proposed to explain the flooding phenomena, in order to improve the fuel cell stack control. Figure 1

Batteries Worth Their Salt: Targeting Next Generation Stationary Storage with Molten Salt Electrolytes

There is an imminent need for batteries capable of meeting the evolving demands of a growing stationary storage landscape, one rich in renewable energy sources and challenged with unprecedented global electrification. Key to our future electrical grid, desirable large-scale, long-duration batteries must not only meet demands for high power and energy density, but they must be safe, cost-effective, and should be sustainably sourced from earth-abundant materials. Here, we will highlight our research and development of low temperature molten salt batteries that employ active materials such as sodium, aluminum, iron, chloride, and iodide. We will demonstrate the promise of our approach through a low-temperature (100°C) molten sodium battery that comprises a molten sodium anode, a solid-state NaSICON ceramic separator, and a low-cost molten metal-halide salt catholyte. These batteries, with remarkable voltages greater than 3.1V, are capable of months of cycling as well as high current charge and discharge behavior, greater than 50mA/cm2. Here, we will not only highlight these performance metrics, but we will describe how we used specialized electrochemical and chemical characterization technique to understand the impacts of molten salt electrolyte composition, electrochemistry, and interfacial interactions on battery performance. By understanding the connections between specific electrochemical phenomena and battery chemistry, we have learned to improve battery performance through tuning of properties, such as molten salt Lewis acidity and current collector composition. This scientifically-motivated battery design approach continues to enable agile innovation and advances to realize the potential of molten salt batteries as a new, impactful stationary storage technology.Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Spectroelectrochemical and Computational Study of Quinoline Based Molecules - Potential Anti-Alzheimer’s Drugs

Here, we present combined experimental and theoretical studies on the spectroelectrochemical properties of 8-aminoquinoline (8AQ). 8AQ is a model molecule for drugs that can chelate copper(II) ions, and thus it may find applications in halting the development of Alzheimer’s disease.Although over a hundred years have passed since Alzheimer’s disease (AD) was first described, it remains incurable to this day. According to one of the leading hypotheses, peptides from the β-amyloid (Aβ) group are responsible for the development of AD. By binding copper(II) ions, Aβs form complexes whose presence promotes the formation of harmful, highly active compounds called reactive oxygen species (ROS) and reactive nitrogen species (RNS). In a series of recent studies, we investigated the differences in electrochemical properties of Cu(II)-complexes with the amyloids Aβ(11-16) and Aβ(3-16) with their pyroglutamated versions, pAβ(11-16) and pAβ(3-16). [1,2] These results showed that the pyroglutamate amyloids are conducive to Cu(II)-reduction at a potential associated with ROS production. Given the abundance of pyroglutamated amyloids in senile plaques, this could have important consequences for AD pathophysiology. Overproduction of ROS and RNS can cause neuron death. Therefore, substances that can aid in removing copper(II) ions from β-amyloids could block the formation of ROS and RNS. Recently, a new quinoline derivative with unique properties has undergone preclinical studies. However, little is known about the redox properties of such molecules, which may be crucial in the early stages of testing potential therapeutic substances.Therefore, we aimed to perform electrochemical and spectroelectrochemical studies of a model molecule, 8-aminoquinoline, whose redox properties were not yet well characterized To fully characterize both anodic and cathodic processes, we used cyclic and pulse voltammetry over a wide range of pH values, including physiological (pH=7.4). In addition, the experimental results were supported by DFT-based computational studies exploring the energy landscapes of the possible reactions and advancing understanding of the electrochemical phenomena.The kind of electrochemical tests presented here may prove of crucial importance for the development of more effective drugs against AD. The high failure rate and relatively poor performance of the recently approved treatment indicates the need to extend preclinical studies with new, so far unused techniques, allowing a more complete picture to be obtained of the effectiveness and toxicity of the potential drug candidates.[1] M.Z. Wiloch, N. Baran, M. Jönsson‐Niedziółka, The Influence of Coordination Mode on the Redox Properties of Copper Complexes with Aβ(3‐16) and Its Pyroglutamate Counterpart pAβ(3‐16), ChemElectroChem. 9 (2022). https://doi.org/10.1002/celc.202200623.[2] M.Z. Wiloch, M. Jönsson-Niedziółka, Very small changes in the peptide sequence alter the redox properties of Aβ(11–16)-Cu(II) and pAβ(11–16)-Cu(II) β-amyloid complexes, Journal of Electroanalytical Chemistry. 922 (2022) 116746. https://doi.org/10.1016/j.jelechem.2022.116746.

Impedance Variation of All-Solid-State Battery Cell Using Li10GeP2S12; States-of-Charge Dependence Visualized by Distribution-of-Relaxation Time Analysis

Electrochemical impedance spectroscopy (EIS) will support understanding of electrochemical phenomena in emerging energy devices, including all-solid-state Li ion batteries (ASSLiBs), only when the results are analyzed in a consistent way without arbitrariness. This study1 aimed to establish such a robust analysis for ASSLiB cells using a fast lithium ion conductor Li10 +x Ge1+x P2 −x S12 (LGPS)2, by applying distribution-of-relaxation time (DRT) analysis3. The DRT method distinctively visualized impedance changes depending on states of charge (SOCs). Pellet-type cells were prepared with an In–Li anode, LGPS separator, cathode composite comprising LGPS and LiNbO3-coated LiCoO2 powders4. Figure 1a shows the discharge curve that was recorded for the cell at the current density of 13.2 μA cm−2 (1/40 C-rate) and with the cut-off voltage of 1.9–3.6 V vs. Li+/In–Li (2.55–4.25 V vs. Li+/Li). The EIS measurements were performed during discharge process at various SOCs from 100% to 20%. Nyquist diagrams obtained from the EIS data are shown in Figure 1b, where two broad semicircles are observed at low and high frequency sides. This result indicates at least two electrochemical processes exist in the cell. Both semicircles become large in size upon decreasing SOCs from 100 % down to 20%, indicating that the cell has SOC-dependent electrochemical processes. Figure 1c shows DRT transformation of the EIS data, which helps to separate impedance components in detail. Here horizonal and vertical axes respectively represent the measurement frequency and polarization contribution at each frequency. The center frequency of each distinct peak corresponds to time constant [τ =1/(2πf)] for the respective electrochemical process, and thus the number of peaks matches that of electrochemical processes in the cell. Meanwhile, the peak area represents polarization contribution of each process. Consistently in the whole SOC range, the above DRT analysis indicates the semicircle at high frequency side is divided into two impedance contributions and that at low frequency side cannot be separated any more. This result is consistent with the DRT spectra from additionally prepared symmetric cells; in total three DRT peaks were observed with two peaks from interphase and interface between In–Li/LGPS, and one from LiNbO3-coated LiCoO2/LGPS interface. Accordingly, DRT diagram in Figure 1c was interpreted as indicated by arrows for each peak. This study demonstrated that DRT analysis supports a consistent interpretation of EIS data from ASSLiB cells at various SOCs and with different electrode configurations, and thus implied that the method will also help subsequent equivalent circuit model analysis for reproducible parametrization of electrochemical processes.1. S. Hori et al., “Understanding the impedance spectra of all-solid-state lithium battery cells with sulfide superionic conductors,” J. Power Sources 556, 232450 (2023).2. N. Kamaya et al., “A lithium superionic conductor,” Nat. Mater. 10, 682–686 (2011).3. S. Dierickx, A. Weber, E. Ivers-Tiffée, “How the distribution of relaxation times enhances complex equivalent circuit models for fuel cells,” Electrochim. Acta 355, 136764 (2020).4. N. Ohta et al., “LiNbO3-coated LiCoO2 as cathode material for all solid-state lithium secondary batteries,” Electrochem. Commun. 9, 1486-1490 (2007). Figure 1

Quantitative regulation of electrochemical-mechanical performance of composite cathode in all-solid-state batteries

The intricate interplay between electrochemical and mechanical phenomena and the volumetric changes leading to interfacial stability within composite cathodes exerts a profound influence on the long-term cycling performance of all-solid-state batteries (ASSBs). This study quantitatively assesses a novel approach aimed at modulating the electrochemical-mechanical performance within composite cathodes by integrating LiNi1−x-yCoxMnyO2 (NCM) with LiCoO2 (LCO) particles. The insightful evaluation is conducted through a multiphysics modeling strategy. The NCM and LCO particles, each displaying distinct open-circuit voltage-concentration relationships, interact and evolve in a two-stage manner during charging, with their coupled electrochemical-mechanical behaviors remaining relatively insensitive to particle positioning. Stage I is dominated by the mechanical response due to NCM particle shrinkage (stress σMises≈1.3 GPa, debonding gap Gd≈1.8 nm). Stage II is governed by the mechanical stress accumulation resulting from the expansion of LCO particles (σMises≈7 GPa, Gd≈62 nm). The choice of solid electrolyte (SE) materials plays a competing role with the modulating of NCM/LCO ratio since SEs possess high compression-bearing capabilities favoring a higher LCO content, while those characterized by robust interfacial strength with particles allow for greater NCM content. Results offer valuable insights into designing more resilient and enduring composite cathodes, unlocking the design and manufacturing of long-cycling ASSBs.

Ultra-thin SiO2 nanoparticle layered separators by a surface multi-functionalization strategy for Li-metal batteries: Highly enhanced Li-dendrite resistance and thermal properties

Mechanical and thermal failure of a polyolefin separator often causes the internal short-circuit of batteries, which leads to abrupt heat generation in a short time, so-called thermal runaway. For this, we introduce grafting polymer layers with cross-linking to make a superior, thin, and uniform SiO2 layer with strong chemical binding to the surface of a polypropylene separator (PPS). The surface of the PPS was modified with i) coating of double bond-contained PVDF, ii) grafting with poly(ethylene glycol) methacrylate, 3-(trimethoxysilyl)propyl methacrylate, and ethylene glycol dimethacrylate, and iii) coating with SiO2 nanoparticles via immersing (GDPS-SNPI) or casting (GDPS-SNPC) methods. The pore structure and distribution, electrolyte affinity, thermal stability, and mechanical properties were progressively improved after respective modification steps. The GDPS-SNPC cell shows excellent capacity retention of 100% at 1 C after 100 cycles and the lowest increase in the cell impedance, whereas the LFP half-cell with PPS exhibited capacity retention of 88.32%. Furthermore, it is found that the coating method for SiO2 nanoparticles substantially influences the long-term cycling stability of Li-symmetric cells. The GDPS-SNPC cell survived after cycling over 1,000 h at a current density of 1 mA cm−2, whereas the GDPS-SNPI cell died before 500 h. Post-mortem analysis of the cycled Li-metal surface shows that smooth Li-plating occurred at the GDPS-SNPC cell, presumably due to a high Li-ion transference number. This work provides a solid methodology for producing a novel and robust separator and advances the understanding of separators' impact on electrochemical and physical phenomena within the cell.

Innovative method for the brine treatment by electrokinetic principles integrated with solar photovoltaic plants

With the growing world population and industrial production, the demand for water has been continuously increasing. By 2030, it was estimated that 60.0 % of the world population will not have access to freshwater, which is about 2.50 % of the total global water. For this, a total of over 17,000 operational desalination plants have been constructed worldwide. However, the key barriers to expansion of the desalination treatments are the brine production and energy consumption. In fact, the brine production is 50.0 % higher than the freshwater, and its treatments could account for 5.0–33.0 % of total desalination cost. Here, a new theoretical approach for brine treatments integrated to solar photovoltaic plants (PVs) to supply renewable energy to the whole system has been proposed. This approach consists in combining electrokinetic and electrochemical phenomena to dilute the brine, by using an alkaline clay with high buffering power. This method substantially desalinates the brine to produce new treated seawater, using clean energy, optimizing energetic and management costs. Some hypotheses and secondary effects should validate the model, e.g., relatively high Ca2+ promotes the electro-migration; the Cl2 production reduces the Cl− concentrations; and the production of H2 can be used to store energy. A practical example for PVPs design is shown.

A multiscale electrochemo-mechanical model of porous electrode in lithium-ion batteries: The coupling of reaction and finite deformation

In this study, we present a novel multiscale electrochemo-mechanical model for porous electrodes in lithium-ion batteries (LIBs). Building upon the theory of finite deformation and the pseudo-two-dimensional framework introduced by Doyle et al. (Journal of the Electrochemical Society, 140, 6(1993)), our model incorporates the interaction between particle deformation and multiscale electrochemical processes, which has been lacking in previous research. The model is validated by the rate performance tests on SiO-based electrodes. By utilizing the model, we analyze the coupling effects among reaction distribution, porosity variation, and local geometrical distortion of the electrode at high current rates. We also investigate the relative importance of different electrochemo-mechanical coupling paths for materials with large volume expansion ratios. Comparing the comprehensive model with simplified versions, we find that diffusion stress is a priority due to its significant impact on ionic diffusion within particles. Porosity variation becomes equally significant at high current rates, as ionic transport in the electrolyte becomes the rate-limiting step. This work contributes to enhance understanding of the interplay between electrochemical and mechanical phenomena in LIB electrodes, especially for silicon-based materials.

Investigation of the lithiation mechanism of tin phosphite SnHPO3 as anode for Lithium-ion batteries

Phosphite-based anodes are attracting increasing attention in energy storage, especially for lithium-ion technology, due to their distinctive structures and their good electrochemical performances. Herein, the lithiation mechanism of tin phosphite SnHPO3 as lithium anode was examined for the first time. SnHPO3 has been synthesized through a soft hydrothermal route. Its structure was characterized by X-ray diffraction, Fourier Transform Infrared spectroscopy and 31P Nuclear Magnetic Resonance spectroscopy techniques. The reaction mechanisms of lithiation-delithiation of SnHPO3 anode was conducted using operando X-ray diffraction, ex-situ X-ray and ex-situ Fourier Transform Infrared spectroscopy techniques at room temperature. Both in-situ and ex-situ measurements show that SnHPO3 undergoes a conversion mechanism. The lithiation-delithiation of tin phosphite took place in a complex redox reaction sequence, and the reversible electrochemical phenomenon exclusively occurs through the alloying of tin at a low potential. The lithiation of tin phosphite begins by partial degradation of its structure, signifying the start of the conversion process. Then, the phosphite matrix becomes amorphous. The reversible capacity of the system is governed by the lithium‑tin alloying de-alloying process, produced at low potential.

Simulation of PEMFC performance

Throughout literature, there are two approaches to estimate fuel cells (FC) performance, by the evaluation of polarization curve. One includes, physical modelling of heat and mass transfer with electrochemical phenomena; the second is based on semiempirical equation used in order to analysis the effect of different physical perturbation on the polarization curve and consider FC as a black box. The aim of this study is to present a simple but enhanced and accurate expression of PEMFC output voltage. The model includes operative conditions, current density and geometric parameter of the FC.

Distribution function of relaxation times: An alternative to classical methods for evaluating the reaction kinetics of oxygen evolution reaction

Reaction kinetics of RuO2 is precisely evaluated by distribution function of relaxation times (DFRT) model using impedance spectroscopy analysis by genetic programming (ISGP). Effective resistances of the Faradaic processes, measured using Electrochemical impedance spectroscopy (EIS) at various overpotentials, were determined utilizing DFRT, by separating and associating three electrochemical phenomena occurring during the reaction. The effective resistances are used to generate a Tafel plot of potential as a function of log1Reff. The classical method, based on linear sweep voltammetry (LSV), to evaluate the Tafel slope is associated with some considerations for accurate results. For RuO2, a reference catalyst, LSV illustrates an average Tafel slope of 182 ± 8 mV/dec while the effective resistance method, estimated using DFRT, shows an average of 181 ± 3 mV/dec. A relative error of 0.3 % between the two methodologies, and a lower standard deviation for DFRT demonstrate the higher precision and effectiveness of ISGP in determining the reaction kinetics via Tafel slope analysis. Therefore, using DFRT with the ability to separate Faradaic from non-Faradaic processes to evaluate the relevant part of the effective resistance, reaction kinetics can be estimated, avoiding shortcomings of the classical Tafel method.

Development of Measurement/Analysis Techniques to Bridge Microscopic and Macroscopic Electrochemical Phenomena in Energy Storage Devices

Development of Measurement/Analysis Techniques to Bridge Microscopic and Macroscopic Electrochemical Phenomena in Energy Storage Devices

Simulation Guided Design of a Hybrid Battery-Type Supercapacitor: A Case Study on MnO2@RVC//AC

Theoretical and experimental understanding of physical and electrochemical mechanisms in hybrid supercapacitors will help improve their energy/power densities. This work explores a simulation-guided design for the fabrication of a high-performance hybrid supercapacitor rendered using optimized COMSOL simulation parameters acquired from Newman’s porous electrode theory. The comprehensive virtual simulations fostered a superior battery-type hybrid electrode with MnO2 nanoclusters formulated over reticulated vitreous carbon. The electrochemical phenomena in the hybrid capacitor were examined using three variables, namely the pore sizes, thicknesses of the positive electrode and the weight ratio of the active material on the negative electrode. The controllable design parameters were identified using numerical simulations and matched with experiments cost-effectively. Thus, the simulations facilitated the experimental fabrication of a superior hybrid battery-type electrode, and charge balancing on the electrodes helped to maximize the energy and power densities. These experimentally validated simulations give new insight that can aid the development of similar hybrid capacitor systems.

Numerical Modeling of Ammonia-Fueled Protonic-Ion Conducting Electrolyte-Supported Solid Oxide Fuel Cell (H-SOFC): A Brief Review

Solid oxide fuel cells with protonic ion conducting electrolytes (H-SOFCs) are recognized and anticipated as eco-friendly electrochemical devices fueled with several kinds of fuels. One distinct feature of SOFCs that makes them different from others is fuel flexibility. Ammonia is a colorless gas with a compound of nitrogen and hydrogen with a distinct strong smell at room temperature. It is easily dissolved in water and is a great absorbent. Ammonia plays a vital role as a caustic for its alkaline characteristics. Nowadays, ammonia is being used as a hydrogen carrier because it has carbon-free molecules and prosperous physical properties with transportation characteristics, distribution options, and storage capacity. Using ammonia as a fuel in H-SOFCs has the advantage of its ammonia cracking attributes and quality of being easily separated from generated steam. Moreover, toxic NOx gases are not formed in the anode while using ammonia as fuel in H-SOFCs. Recently, various numerical studies have been performed to comprehend the electrochemical and physical phenomena of H-SOFCs in order to develop a feasible and optimized design under different operating conditions rather than doing costlier experimentation. The aim of this concisely reviewed article is to present the current status of ammonia-fueled H-SOFC numerical modeling and the application of numerical modeling in ammonia-fueled H-SOFC geometrical shape optimization, which is still more desirable than traditional SOFCs.

(Invited) Theoretical Analysis of Reaction Inhomogeneity and Lithium Plating Onset at Fast Charge Rates for Lithium Ion Batteries

Inhomogeneous reactions in porous anodes may lead to lithium plating at high C-rates. Inhomogeneous lithium intercalation behavior in cathodes and anodes has been studied on particle and macroscale (i.e., cell) length scales. The effects of various physical and electrochemical phenomena (e.g., ionic transport, mass transport, interface reaction kinetics, and electrode thermodynamic behavior) have been studied in the context of reaction inhomogeneity. However, an accurate theoretical understanding of how these accelerate lithium metal plating has not been established in fast charging applications. Here, analytical and numerical modeling is used to develop a more complete understanding of how these coupled, nonlinear electrochemical and physical effects interplay to cause lithium plating. Specifically, it is shown that simple analytical solutions (which are functions of one or several nondimensional numbers) can with surprising accuracy approximate the onset of lithium plating predicted by calibrated numerical models of graphite half-cells. These analytical and numerical results are compared against in situ experimental observations of lithium plating onset during fast charging. This work attempts to use simplified analytical analysis to clarify and unify findings in more complex numerical models, which can ultimately provide strategies for mitigating Li metal plating during fast charging. Application of this theory for design and optimization of electrodes with engineered architectures is discussed.

(Keynote) Modeling Battery Performance Due to Volume Change in Porous Electrodes Towards the Development of Electrified Propulsion Systems

In order to accurately predict the behavior of electrochemical devices, it is necessary to develop sophisticated models that take into consideration transport processes, electrochemical phenomena, mechanical stresses, and structural deformations on the operation of an electrochemical system. Several different models exist that can predict the electrochemical performance of these devices under a variety of operating and design conditions. However, in many of these models, the porosity of a porous electrode is often assumed to be constant since the volume changes seen during the intercalation reaction can be small. However, electrode materials developed in recent years show significant volume changes during intercalation, which are unable to be accurately predicted using these constant porosity models.Porosity and dimensional changes in an electrode can significantly affect the resistance of the battery during cycling and can cause premature failure of the battery due to generated stresses. Over the past decade and a half, we have shown the ability to incorporate dimensional and porosity changes in a porous electrode during intercalation through the coupling of various mechanics treatments with porous electrode theory. Many assumptions were used to obtain an analytical solution, including the assumption of bulk strain, uniform porosity, and uniform concentration across the electrode.[1-4] This model was extended to look at design considerations as well as non-uniformity within a single porous electrode coupled to a lithium metal reference.[5] This model was further improved by removing some of the earlier assumptions and is capable of illustrating the development of stress, strain gradients, and porosity gradients across a porous electrode during cycling in a battery containing a blended anode undergoing volume change coupled to an NMC cathode.[6] The reversible volume change predictions were then validated using data from pouch cells seen in the Chevrolet Volt.[7] Following our validation studies, we illustrated the impact that coupled electrochemical-mechanical volume change can have on electric vehicle battery pack design.[8] References P. M. Gomadam and J. W. Weidner, J Electrochem Soc, 153, A179 (2006).T. R. Garrick, K. Kanneganti, X. Y. Huang and J. W. Weidner, J Electrochem Soc, 161, E3297 (2014).T. R. Garrick, Y. Dai, K. Higa, V. Srinivasan and J. W. Weidner, Ecs Transactions, 72, 11 (2016).T. R. Garrick, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3552 (2017).T. R. Garrick, K. Higa, S.-L. Wu, Y. Dai, X. Huang, V. Srinivasan and J. W. Weidner, J Electrochem Soc, 164, E3592 (2017).D. J. Pereira, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 166, A1251 (2019).D. J. Pereira, M. A. Fernandez, K. C. Streng, X. X. Hou, X. Gao, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 167, 080515 (2020).D. J. Pereira, A. M. Aleman, J. W. Weidner and T. R. Garrick, J Electrochem Soc, 169, 020577 (2022).