Exchange Currents Research Articles

Investigate of Electrochemical Properties of Nd(II) and Nd(III) in Eutectic LiCl-KCl Molten Salt

Pyroprocessing is one of the promising methods to reprocess the spent nuclear fuel. Neodymium (Nd) constitutes about one third of rare earth in fission products, however, the electrochemical properties of Nd have not been thoroughly understood, especially the exchange current. In the present study, the transit electrochemical methods of cyclic voltammetry and square wave voltammetry were applied to study the properties of Nd in LiCl-KCl system. The reduction of Nd3+ was determined as a two-step reaction with Nd3+/Nd2+ to be a reversible but Nd2+/Nd to be a quasi or irreversible reactions. Additionally, parameters such as the diffusion coefficient, exchange current, and apparent potential were derived from the cyclic voltammetry curves. Their relationship with temperature and concentration was investigated under 723 K, 773 K, 823 K with concentrations of 3 wt%, 6 wt% and 9 wt%. The present study contributes significantly to rich the database of Nd in LiCl-KCl molten salt and to understand the electrochemical behaviors of Nd during electrochemical separation of spent nuclear fuel.

Helium-4 gravitational form factors: Exchange currents

Helium-4 gravitational form factors: Exchange currents

Exploring the thermodynamics and dynamics of lithium ions inserted into Li1-xMn2O4 electrode at different temperatures

Efficient lithium extraction via electrochemical adsorption holds great promise for resource utilization and energy storage. However, the mechanism of how temperature influences the electrochemical adsorption process, particularly the thermodynamics and dynamics in the liquid, liquid–solid interface, and solid remains unclear. To address this challenge, we explored the impact of temperature (273.15 to 328.15 K) using Li1-xMn2O4 as an adsorbent. For the liquid phase, the conductivity increased from 0.89 to 0.95 S/m following lnΛ = -0.11(1000/T) + 0.27 in thermodynamics; the solution viscosity decreased from 1.71 × 10-3 to 5.15 × 10-4 Pa·s conforming lnη = 1.96(1000/T) − 13.54 in dynamics. For the liquid–solid interface, the charge transfer resistance (Rct) decreased from 42.03 to 25.17 ohm obeying ln(1/Rct) = -0.82(1000/T) − 0.69 in thermodynamics; the exchange current (i0) showed a positive correlation with temperature in fitting Logi0 = -0.50(1000/T) − 1.40 in dynamics. For the solid phase, the increase in reduction peak voltage (ERP) and the decrease in Gibbs free energy (G), entropy (S), and enthalpy (H) all indicate that the increase of temperature promotes lithium ions to inserted into Li1-xMn2O4 in thermodynamics; the increased diffusion coefficient (DLi+(S)) and higher reduction peak current (IRP) suggest that higher temperature strengthens lithium ions diffusion and insertion in dynamics. In the temperature range, the adsorption capacity gradually increased from 1.15 to 7.37 mg/g, the initial current enhanced from −3.40 × 10-4 to −1.85 × 10-3 A, the terminal current raised from −1.59 × 10-4 to −7.40 × 10-4 A, and the current efficiency improved from 31.28 % to 66.11 % in the temperature range. This work provides a deeper understanding of the impact of temperature on the electrochemical lithium adsorption process from thermodynamics and dynamics. This work also offers crucial guidance for the upgrading of electrochemical lithium adsorption technology and can be applied to other fields such as energy storage, catalysis, and synthesis, providing a valuable reference for optimizing reaction parameter design in thermodynamics and dynamics.

(Keynote) Unified Quantum Theory of Electrochemical Kinetics Based on Coupled Ion-Electron Transfer

A general theory of coupled ion–electron transfer (CIET) is presented, which unifies quantum kinetics of electron transfer (ET) with classical kinetics of bond-breaking ion transfer (IT) in a general framework of non-equilibrium thermodynamics [1]. In the limit of large reorganization energy, the theory predicts Marcus kinetics of “electron-coupled ion transfer” (ECIT). In the limit of large ion-transfer energies, the theory predicts generalized Butler–Volmer kinetics of “ion-coupled electron transfer” (ICET), where the charge transfer coefficient and exchange current are connected to microscopic properties of the electrode/electrolyte interface. In the ICET regime, the reductive and oxidative branches of Tafel’s law are predicted to hold over a wide but finite range of overpotentials, bounded by the ion-transfer energies for oxidation and reduction, respectively. The probability distribution of transferring electron energies in CIET smoothly interpolates between a shifted Gaussian distribution for ECIT (as in the Gerischer–Marcus theory of ET) to an asymmetric, fat-tailed Meixner distribution centered at the Fermi level for ICET. The latter may help interpret asymmetric line shapes in x-ray photo-electron spectroscopy (XPS) and Auger electron spectroscopy (AES) for oxidized metal surfaces in terms of shake-up relaxation of the ionized atom and its image polaron by ICET. In the limit of large overpotentials, the theory predicts a transition to inverted Marcus ECIT, leading to a universal reaction-limited current for metal electrodes, dominated by barrierless quantum transitions. Uniformly valid, closed-form asymptotic approximations are derived that smoothly transition between the limiting rate expressions for ICET and ECIT for metal electrodes, using simple but accurate mathematical functions. The theory is applied to lithium intercalation in lithium iron phosphate (LFP) and found to provide a consistent description of the observed current dependence on overpotential, temperature and concentration, learned from x-ray images [2]. CIET theory thus provides a critical bridge between quantum electrochemistry and electrochemical engineering.[1] M. Z. Bazant, Unified quantum theory of electrochemical kinetics by coupled ion-electron transfer, Faraday Discussions 246, 60-124 (2023).[2] H. Zhao, H. D. Deng, A. E. Cohen, J. Lim, Y. Li, D. Fraggedakis, B. Jiang, B. D. Storey, W. C. Chueh, R. D. Braatz, and M. Z. Bazant, Learning heterogeneous reaction kinetics from X-ray movies pixel-by-pixel, Nature 621, 289-294 (2023). Figure 1

(Invited) Understanding the Effect of Cell Assembly and Operation on AEM Electrolyzer Performance and Durability

Water electrolysis to produce hydrogen is gaining significant attention due to a significant decrease in the cost of renewable energy sources such as solar, wind, and tidal etc. Among the existing water electrolysis technologies, anion exchange membrane water electrolysis has recently emerged due to its potential advantages over proton exchange membrane electrolysis and traditional alkaline electrolysis. Anion exchange membrane electrolyzers (AEMELs) can allow for the use of PGM-free electrocatalysts and low-cost component materials due to its less corrosive alkaline environment while also enabling electrochemical H2 compression.An overwhelming majority of the research that is going on related to AEMELs is the synthesis of advanced functional nanomaterials – e.g. new catalysts and membranes. Though these are critically important components of the cell, their function is supported by a multitude of other factors. For example, it is well-known that water and gas transport in the electrodes is highly dictated by the porous transport layers. The electrode fabrication technique controls the electrode morphology. The synthesis method for the catalyst determines its porosity and structure. The cell gasketing controls compression. The operating current density and temperature affect stress at the material and electrode level, and dictate other properties such as exchange current, ionic conductivity, water uptake, diffusivities, etc. Many of these properties are less reported and will be the subject of this presentation.This presentation will focus on understanding how various decisions that are made regarding electrode fabrication, cell assembly and cell operation affect the operating voltage and voltage stability of AEM electrolyzers. The goal of this talk is to combine electrochemical and physical characterization data to develop a series of guiding principles for AEMEL operation that can be used across polymer chemistries and catalyst selection.

Deuteron gravitational form factors: Exchange currents

Deuteron gravitational form factors: Exchange currents

Effects of Acute Hypernatremia on the Electrophysiology of Single Human Ventricular Cardiomyocytes: An In Silico Study.

Clinical and experimental data on the cardiac effects of acute hypernatremia are scarce and inconsistent. We aimed to determine and understand the effects of different levels of acute hypernatremia on the human ventricular action potential. We performed computer simulations using two different, very comprehensive models of the electrical activity of a single human ventricular cardiomyocyte, i.e., the Tomek-Rodriguez model following the O'Hara-Rudy dynamic (ORd) model and the Bartolucci-Passini-Severi model as published in 2020 (known as the ToR-ORd and BPS2020 models, respectively). Mild to extreme levels of hypernatremia were introduced into each model based on experimental data on the effects of hypernatremia on cell volume and individual ion currents. In both models, we observed an increase in the intracellular sodium and potassium concentrations, an increase in the peak amplitude of the intracellular calcium concentration, a hyperpolarization of the resting membrane potential, a prolongation of the action potential, an increase in the maximum upstroke velocity, and an increase in the threshold stimulus current at all levels of hypernatremia and all stimulus rates tested. The magnitude of all of these effects was relatively small in the case of mild to severe hypernatremia but substantial in the case of extreme hypernatremia. The effects on the action potential were related to an increase in the sodium-potassium pump current, an increase in the sodium-calcium exchange current, a decrease in the rapid and slow delayed rectifier potassium currents, and an increase in the fast and late sodium currents. The effects of mild to severe hypernatremia on the electrical activity of human ventricular cardiomyocytes are relatively small. In the case of extreme hypernatremia, the effects are more pronounced, especially regarding the increase in threshold stimulus current.

Two-dimensional MXene supported Ru-Cr(OH)x clusters as an efficient electrocatalyst for hydrogen oxidation reaction

The development of high-performance non-platinum catalysts remains a key challenge for the practical application of anion-exchange membrane fuel cells due to the sluggish kinetics response of the hydrogen oxidation reaction (HOR) in alkaline electrolytes. Herein, we report an outstanding HOR electrocatalyst using a facile one-step method with the two-dimensional double transition metal MXene (Mo2TiC2Tx) as a carrier mixed with metallic ruthenium and Cr(OH)x clusters (Ru-Cr(OH)x/MXene). Specifically, the as-prepared Ru-Cr(OH)x/MXene electrocatalyst exhibits a high apparent kinetic current (jk) of 18.32 mA cm−2 and exchange current (j0) of 1.64 mA cm−2 at an overpotential of 50 mV, respectively, which are 4.74 and 1.46 times as high as those of Pt/C catalyst. Additionally, mechanism experiments indicated that the Ru-Cr(OH)x/MXene electrocatalyst could attenuate the adsorption of hydrogen intermediate (Had) and enhance the adsorption of hydroxyl species (OHad) to promote CO oxidation, which resulted in a significant increase in the HOR activity and enhanced tolerance to CO. Furthermore, combining theoretical studies via density functional theory calculations, our work confirm that the interaction effect of each components of Ru-Cr(OH)x/MXene can optimize the binding energy of the Had and OHad for the HOR. This work develops a new approach to design of HOR electrocatalyst with MXene-based materials.

Meson Exchange Currents in the Clothed-Particle Representation: Calculation of the Deuteron Magnetic Form Factor

Meson Exchange Currents in the Clothed-Particle Representation: Calculation of the Deuteron Magnetic Form Factor

Computational investigation of hydrogen evolution reaction on transition metal-doped monolayer VSe2: A DFT approach

Density functional theory (DFT) was used to investigate the hydrogen evolution reaction (HER) on monolayer VSe2 doped by transition metal (TM) (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rh, Ir), in which Se or V is replaced by TM atoms (denoted as TM@Se or TM@V). Introducing transition metals (TMs) into the VSe2 monolayer can alter its electronic structure and catalytic properties. The choice of transition metal dopants and their configurations can significantly impact the catalytic performance of the material. It is illustrated that the TM@V systems are more stable than TM@Se configurations. Moreover, Co@V, Cu@V, Fe@V Zn@V and Cu@Se exhibit the lower ΔGH* values of 0.07, 0.09, 0.10, 0.12 and −0.1 eV, respectively, and ΔGH* values are very close to the ideal value of zero and are superior to precious metal Pt (ΔGH* = −0.1eV). Based on the scaling relationship of ΔGH* of H* intermediate, the volcano diagram and exchange current density diagram are established. It is predicted that Cu@V, Co@V, Fe@V, Zn@V structures could provide large exchange current of −1.6, −1.22, −1.7, −2 i0/(Acm−2), respectively.

Electrochemical behavior of aluminum in 1-ethyl-3-methylimidazolium chloroaluminate ionic liquids

The mechanism of electrochemical oxidation and reduction of aluminum in 1-ethyl-3-methylimidazolium-based (EMImCl) chloroaluminate ionic liquids is studied across the concentration range of N = 1.1–2.0 (N the molar ratio of AlCl3 to EMImCl) at temperatures between 303 K and 418 К. Anodic stationary polarization curves (SPCs) indicate that the process of anodic dissolution of aluminum is complicated by passivation. The current density in the passive region and the passivation potential decrease with a higher concentration of Al2Cl7– ion in the melt. To elucidate the processes taking place at the aluminum electrode, the relationship between the concentration of the ions in the vicinity of the electrode and the potential applied in the cathodic and anodic region was analyzed by in-situ Raman spectroscopy for the concentrations of N = 1.1 and 2.0. The resulting dependences of relative peak intensity vs. potential correlate with the cathodic and anodic polarization curves. In the anodic region the content of Al2Cl7– grows with the potential, while the concentration of AlCl4– ion decreases. In the cathodic region the opposite process is observed: the concentration of Al2Cl7– decreases and that of AlCl4–increases with growing potential. It is shown that a precipitate of AlCl3 forms on the electrode surface in the region of passive aluminum dissolution, which is responsible for the electrode passivation. Based on the results obtained, we propose a model for the process of aluminum oxidation/reduction preceded and followed by a chemical reaction of aluminum chloride formation for the cathodic and anodic process, respectively. Temperature dependences of diffusion coefficients are studied by chronopotentiometry. The results indicate that diffusion coefficients are not affected by the concentration across the temperature range studied. The activation energy for diffusion was found to be 13.65 kJ∙mol−1. Impedance spectroscopy was used to investigate the concentration and temperature dependences of exchange current density. The exchange currents increase with increasing aluminum chloride content in the melt. The transfer coefficient and electrochemical reaction rate constant were found to be α = 0.17 ± 0.04, ks = (1.7 ± 0.4)∙10−6 cm∙s−1, respectively. The activation energy for the electrochemical reaction rate constant does not depend on the concentration and was found to be 33.5 kJ∙mol−1.

Theoretical framework for mixed-potential-driven catalysis.

Mixed-potential-driven catalysis is expected to be a distinctive heterogeneous catalytic reaction that produces products different from those produced by thermal catalytic reactions without the application of external energy. Electrochemically, the mechanism is similar to that of corrosion. However, a theory that incorporates catalytic activity as a parameter has not been established. Herein, we report the theoretical framework of mixed-potential-driven catalysis, including exchange currents, as a parameter of catalytic activity. The mixed potential and partitioning of the overpotential were determined from the exchange current by applying the Butler-Volmer equation at a steady state far from equilibrium. Mixed-potential-driven catalysis is expected to open new areas not only in the concept of catalyst development but also in the field of energetics of biological enzymatic reactions.

Identifying Electrocatalytic Activity Sequence of Metal Phthalocyanines for the Hydrogen Peroxide Oxidation Reaction

The hydrogen peroxide oxidation reaction (HPOR) plays a vital role in the emerging H2-H2O2 cycle energy storage system, in which the rational design of HPOR electrocatalyst is essential for achieving high system efficiency. Herein, we establish the HPOR activity trends using structurally well-defined metal phthalocyanines (MPc) as model catalysts via a combined experimental and computational approach. The measured activity sequence follows the order of CoPc > FePc > MnPc > ZnPc > H2Pc > NiPc > CuPc based on their site-normalized exchange current (i 0-s). Theoretical calculations indicate that the binding free energy of hydroperoxyl intermediate, HOO*, on MPc (ΔG HOO*) is the activity descriptor for HPOR. A volcano-type activity trend is observed by correlating the logarithm of i 0-s (logi 0-s) with the ΔG HOO* values and agrees with the theoretical predictions. This HPOR activity trend provides insights into the design of highly active electrocatalysts for HPOR and related energy applications.

Renewal of electrical energy by green hydrogen using a metal organic framework with Fe3O4 cluster

Recently, metal-–organic frameworks (MOFs) with high porosity have drawn extensive attention in water splitting. The present study reports the synthesis of a porous Fe-based MOF by a modified precursor made of magnetite (Fe3O4). Subsequently, a series of undoped and lanthanide -doped (MOFs) are prepared using the solvothermal method. The synthesis provided a high surface area with a high specific surface and pore volume. The synthesized electrocatalyst with a high surface area is demonstrated as an excellent electrocatalyst for the hydrogen evolution reaction(HER) investigated in acidic media. The electrochemical results demonstrated low Tafel slopes (81 and 166 mV dec–−1), high exchange current, high ssurface area (Cdl) (148.29 and 150.57 mV), and high stability for Au/MIL-53 (Fe)/Gd-Fe3O4 and glassy carbon electrode GCE/MIL-53 (Fe)/La-Fe3O4. The high activity is attributed to the large surface area of the synthesized Fe/ Fe3O4-based MOF, which is porous and magnetic. The effect of base metal on catalyst performance was discussed. Through the unification of two catalytically active metals as lanthanide, a new opportunity opens up for the development of synergistic systems in multiple applications.

Hypertrophic cardiomyopathy dysfunction mimicked in human engineered heart tissue and improved by sodium-glucose cotransporter 2 inhibitors.

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiomyopathy, often caused by pathogenic sarcomere mutations. Early characteristics of HCM are diastolic dysfunction and hypercontractility. Treatment to prevent mutation-induced cardiac dysfunction is lacking. Sodium-glucose cotransporter 2 inhibitors (SGLT2i) are a group of antidiabetic drugs that recently showed beneficial cardiovascular outcomes in patients with acquired forms of heart failure. We here studied if SGLT2i represent a potential therapy to correct cardiomyocyte dysfunction induced by an HCM sarcomere mutation. Contractility was measured of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) harbouring an HCM mutation cultured in 2D and in 3D engineered heart tissue (EHT). Mutations in the gene encoding β-myosin heavy chain (MYH7-R403Q) or cardiac troponin T (TNNT2-R92Q) were investigated. In 2D, intracellular [Ca2+], action potential and ion currents were determined. HCM mutations in hiPSC-CMs impaired relaxation or increased force, mimicking early features observed in human HCM. SGLT2i enhance the relaxation of hiPSC-CMs, to a larger extent in HCM compared to control hiPSC-CMs. Moreover, SGLT2i-effects on relaxation in R403Q EHT increased with culture duration, i.e. hiPSC-CMs maturation. Canagliflozin's effects on relaxation were more pronounced than empagliflozin and dapagliflozin. SGLT2i acutely altered Ca2+ handling in HCM hiPSC-CMs. Analyses of SGLT2i-mediated mechanisms that may underlie enhanced relaxation in mutant hiPSC-CMs excluded SGLT2, Na+/H+ exchanger, peak and late Nav1.5 currents, and L-type Ca2+ current, but indicate an important role for the Na+/Ca2+ exchanger. Indeed, electrophysiological measurements in mutant hiPSC-CM indicate that SGLT2i altered Na+/Ca2+ exchange current. SGLT2i (canagliflozin > dapagliflozin > empagliflozin) acutely enhance relaxation in human EHT, especially in HCM and upon prolonged culture. SGLT2i may represent a potential therapy to correct early cardiac dysfunction in HCM.

Effect of tunable composition-shape of bio-inspired Pt NPs electrocatalyst in direct methanol fuel cell: Process optimization and kinetic studies

Highly efficient bio-inspired platinum nanoparticles (Pt NPs) as an electrocatalyst with superior intrinsic kinetics and high performance for methanol oxidation reaction (MOR) derived from green synthesis of bio-waste utilization is of great interest. The bio-inspired Pt NPs were examined for their kinetic parameters in terms of the Tafel plot, exchange current, square root of the scan rate, methanol diffusion coefficient, activation energy (Ea), and factors influencing current density. Bio-inspired Pt NPs exhibit a fast kinetic reaction with a low Tafel value of 179 mV dec−1 and exchange current, α = 0.33, compared to commercial Pt black (233 mV dec−1, α = 0.25). The bio-inspired Pt NPs display low activation energy, Ea, as the potential increases, indicating improved intrinsic kinetics, and the MOR catalyzed by bio-Pt NPs was discovered to be a diffusion-controlled process. The parametric effect of bio-inspired Pt NPs concentration has a crucial influence on the anisotropic morphological structure and interconnection to the current density (mA mg−1) of MOR. Central Composite Design (CCD) was applied for RSM-based modeling and analyzing the parameter effects, including bio-inspired Pt NPs concentration, methanol concentration, and electrocatalyst loading to optimize the current density. The optimized current density produced by bio-inspired Pt NPs was 640.11 mA mgPt−1 at ideal conditions of 1.5 mM bio-Pt NPs, 1.05 M CH3OH, and 2.14 mg. Ultimately, the passive DMFC single-cell powered by bio-inspired Pt NPs generates power density with Pmax of 5.70, 6.67, and 8.28 mW cm−2 at 25, 80, and 100 °C. Thus, bio-inspired Pt NPs derived from green synthesis pathways and biomass-mediated extract have been proven to be viable and sustainable anode electrocatalysts for utilization in the energy conversion of renewable energy with outstanding performance.

N-Coordinated Iridium-Molybdenum Dual-Atom Catalysts Enabling Efficient Bifunctional Hydrogen Electrocatalysis.

Achieving effective hydrogen evolution/oxidation reaction (HER/HOR) across a wide pH span is of critical importance in unlocking the full potential of hydrogen energy but remains intrinsically challenging. Here, we engineer the N-coordinated Ir-Mo dual atoms on a carbon matrix by ultrafast high-temperature sintering, creating an efficient bifunctional electrocatalyst for both HER and HOR in both acidic and alkaline electrolytes. The optimized catalyst, Ir-Mo DAC/NC, demonstrates exceptional performance, with a significantly reduced HER overpotential of 11.3 mV at 10 mA/cm2 and a HOR exchange current (i0,m) of 3972 mA/mgIr in acidic conditions, surpassing the performance of Pt/C and Ir/C catalysts. In alkaline conditions, Ir-Mo DAC/NC also outperforms Pt/C, as evidenced by its low HER overpotential of 23 mV at 10 mA/cm2 and a high i0,m of 1308 mA/mgIr. Furthermore, our catalyst exhibits remarkable stability in both acidic and alkaline environments. DFT calculations results reveal that the superior electrochemical performance of Ir-Mo DAC/NC arises from the electronic synergy between Ir and Mo pairs, which regulates the interaction between the intermediates and active sites. These findings present a promising strategy for the development of dual-atom catalysts (DACs), with potential applications in the polymer fuel cells and water electrolyzers.

Electrochemical Characterization of Stable Cu(II)/Cu(I) Electrolytes for Redox Flow Battery

The path to reach carbon neutrality cannot be paved without further development of long life and low-cost batteries, considering also cyclability, calendar life, and round-trip efficiency. In this context, Redox Flow Batteries (RFB) have gathered researchers’ attention as possible candidates to play a major role in the incoming of the next generation batteries. Their unique capability to decouple power and energy makes possible of have flexible modular design and operation, along with outstanding scalability, plus moderate maintenance costs and long-life cycling. [1]Although vanadium based redox flow batteries (VRFB) have been the most studied and commercialized RFB system, in the past years concern has been raised due to vanadium toxicity, low availability and high costs. On the other hand, copper redox flow batteries (CuRFB) have the possibility of using different membranes than expensive perfluorinated ones, furthermore, copper has more competitive costs and a well-consolidated value chain in Europe when compared to vanadium. [2]In this study, the effect of the copper-chloride complexes used to stabilize electrolytes for CuRFB was investigated, as well as the influence of secondary cations from the supporting electrolyte, e.g., Ca2+, K+, H+. Different solutions with Cu:Cl ratio varying from 1:4 to 1:9 were characterized by physical-chemical and electrochemical methods. It was observed that the chloride complexation efficiently stabilized cuprous cations, at room temperature (Figure 1), avoiding metal Cu to be formed. Obtained diffusion coefficients (D0 ) for Cu2+ and Cu+ showed that mobility of the species is influenced by the concentration of the copper itself, and also by Cl- and the secondary cation concentration. Solutions with 2M of Cu2+ shown higher values of D0 compared to 1M, though with reduced reversibility.Highly concentrated CaCl2 solutions, 1 to 4 M, were used as Cl- is required to form stable [CuClx]2-x complexes, however high Ca2+ concentration might compete with copper species to form [CaClx]2-x, which limits the availability of complexing ligand for Cu+. [3] HCl was then used as additive to enhance the conductivity of the solution while it allows to reduce the CaCl2 concentration by keeping the same molar proportion. Plus, it promoted higher mobility of copper species, with and values about ten times higher than without acid.Finally, further discussions will be conducted with the aid of electrochemical parameters such as kinetic and exchange currents, along with the heterogenous rate constant and the Nicholson parameter, besides conductivity and viscosity of the solutions, to evaluate ligand composition effect on the Cu2+/Cu+ reaction kinetics and overall battery performance.AcknowledgementsThis work is funded by the Italian Ministry of Enterprises and Made in Italy in the framework of the Important Project of Common European Interest (IPCEI) European Battery Innovation (project IPCEI Batterie 2 - CUP: B62C22000010001). The IPCEI European Battery Innovation is also funded by public authorities from Austria, Belgium, Croatia, Finland, France, Germany, Greece, Poland, Slovakia, Spain and Sweden.

Use of Surface Features with Controlled Kinetics to Verify Fits of Scanning Electrochemical Microscopy Images

Scanning Electrochemical Microscopy (SECM) is a promising technique for measuring kinetics of redox reactions at surfaces. The conversion of the current map - produced by rastering an electrode over the surface - to a maps of the rate constant of reactions at the surface requires computer modelling and statistical techniques. Experimentally obtained SECM images are necessary to validate computer models that will be used to test these fitting procedures.The largest challenge was finding or creating samples that have reactive sites of known kinetics that were sufficiently slow to be activation-limited. This was achieved by producing small precious metal electrodes embedded in an insulating surface. The exchange currents of these electrodes were characterized using cyclic voltammetry at high scan rates[1,2] so that the rate constant of the electrodes could be effectively controlled by the potential at which they were poised. SECM images of these electrodes can compared to computer simulations to verify that they produced correct results. [1] Nicholson, R.S. Theory and Application of Cyclic Voltammetry for Measurement of Electrode Reaction Kinetics. Anal. Chem. 1965, 37, 11, 1351–1355[2] Mirkin, M.V.; Bard, A.J. Simple Analysis of Quasi-Reversible Steady-State Voltammograms. Anal. Chem. 1992, 64, 19, 2293–2302

Modulating Li-ion battery voltage oscillations in phase field simulations

The discovery of voltage oscillations in Li-ion batteries has shown how complex phase separating electrodes can be. It is still poorly understood how electrode particles can act in this concerted manner to give out the oscillations, implying possible material behavior and applications are still undiscovered. For a systemic study in this direction, however, an initial understanding of how parameters impact the voltage oscillations is required. In this work, we investigate the roles of electrolyte mass transport and surface wetting on voltage oscillations. Using data from the mass transport investigation, it is discussed how particle phase transitioning is ordered by their radius and distance from the separator, shaping voltage oscillations at low discharge capacities. Special attention is drawn to electrode porosity, given its role in the interplay between intercalation kinetics and electrolyte mass transport, influencing the overall oscillation amplitude. At last, the oscillations were found to be greatly affected by surface wetting, with results predicting a 200 % increase in oscillation amplitude, and drastic changes to oscillation period and shape. The reason for this could be traced back to the exchange current, as this magnitude is dependent on surface Li+ concentration. The largest increase in amplitude and period was associated with a change in the intraparticle phase transitioning dynamics. The results are used to formulate recommendations to experimentalists on how to enhance the oscillatory response, and are also employed in reinterpreting previous experimental reports.