A Bayesian view on the Hilbert transform and the Kramers-Kronig transform of electrochemical impedance data: Probabilistic estimates and quality scores

Water Management Fault Diagnosis by Operando Distribution of Relaxation Times Analysis for Anion Exchange Membrane Fuel Cells

Timely and effective fault diagnosis is essential to ensure the reliability and longevity of anion exchange membrane fuel cells (AEMFCs). This study employs operando electrochemical impedance spectroscopy (EIS) measurements and distribution of relaxation times (DRT) analysis to detect water management faults in both anode and cathode electrodes. EIS measurements are performed under diverse operating conditions, revealing three distinct frequency ranges associated with ion transport, charge transfer, and mass transport processes, and elucidating their contributions to voltage loss. Building on these findings, DRT analysis is further applied to explore the behavior and variation of polarization impedance under different water management fault conditions. Compared with the reference case, anode flooding reduces ion transport resistance by up to 37.1%, while increasing charge transfer and mass transport resistances by 61.8% and 219.2%, respectively. Conversely, cathode flooding results in a 33.5% increase in charge transfer resistance, with minimal impact on mass transport resistance. These quantitative insights provide a novel and effective diagnostic tool for distinguishing water management fault types (flooding or drying) and their location (anode or cathode), offering valuable data to support the implementation of water management control strategies that enhance performance and extend the lifespan of commercial AEMFC stacks.

Li-Si alloy pre-lithiated silicon suboxide anode constructing a stable multiphase lithium silicate layer promoting Ion-transfer kinetics

Enhancing the initial Coulombic efficiency (ICE) and cycling stability of silicon suboxide (SiOx) anode is crucial for promoting its commercialization and practical implementation. Herein, we propose an economical and effective method for constructing pre-lithiated core-shell SiOx anodes with high ICE and stable interface during cycling. The lithium silicon alloy (Li13Si4) is used to react with SiOx in advance, allowing for improved ICE of SiOx without compromising its reversible specific capacity. The pre-lithiated surface layer contains uniform multiphase lithium silicates (L2SiO3, Li4SiO4, and Li2Si2O5) in the nanoscale. This multiphase lithium silicate layer exhibits mechanical robustness against variation of micro-stress, which can act as a buffer layer to relieve volume variation. In addition, analysis of dynamic electrochemical impedance spectroscopy (dEIS) and distribution of relaxation time (DRT) confirm that the multiphase lithium silicate layer enhances Li-ion diffusion kinetics and contributed to constructing stable SEI. As a result, the optimal L10-850 anode shows a high ICE of 85.3 %, together with a high specific capacity of 1771.5mAh mg-1. This work gives a perspective strategy to modify SiOx anodes by constructing a pre-lithiated surface layer with practical application potentials.

Enhanced Surface Plasmon Resonance Sensing via Kramers-Kronig Phase Extraction

This study introduces a novel approach to enhance surface plasmon resonance (SPR) sensing using Kramers-Kronig (K-K) relations for phase extraction from reflection spectra. By applying the K-K relations, a phase shift sensitivity of 3400°/RIU is achieved improving SPR detection limits to 9 × 10-6 RIU, which is four times more sensitive than conventional methods for determining SPR peak shifts. This advancement enables more precise detection of refractive index changes in aqueous solutions, making it valuable for biosensing and environmental monitoring with spectrometers.

Low-Concentration Redox-Electrolytes for High-Rate and Long-Life Zinc Metal Batteries

The uncontrolled zinc electrodeposition and side reactions severely limit the power density and lifespan of Zn metal batteries. Herein, the multi-level interface adjustment effect is realized with low-concentration redox-electrolytes (0.2 m KI) additives. The iodide ions adsorbed on the zinc surface significantly suppress water-induced side reactions and by-product formation and enhance the kinetics of zinc deposition. The distribution of relaxation times results reveal that iodide ions can reduce the desolvation energy of hydrated zinc ions and guide the deposition of zinc ions due to their strong nucleophilicity. As a consequence, the Zn||Zn symmetric cell achieves superior cycling stability (>3000 h at 1 mA cm-2, 1 mAh cm-2) accompanied by a uniform deposition and a fast reaction kinetics with a low voltage hysteresis (<30 mV). Additionally, coupled with an activated carbon (AC) cathode, the assembled Zn||AC cell delivers a high-capacity retention of 81.64% after 2000 cycles at 4 A g-1. More importantly, the operando electrochemical UV-vis spectroscopies show that a small number of I3 - can spontaneously react with the dead zinc as well as basic zinc saltsand regenerate iodide ions and zinc ions; thus, the Coulombic efficiency of each charge-discharge process is close to 100%.

Ultrafast Dual-Shock Chemistry Synthesis of Ordered/Disordered Hybrid Carbon Anodes: High-Rate Performance of Li-Ion Batteries

Graphite exhibits crystal anisotropy, which impedes the mass transfer of ion intercalation and extraction processes in Li-ion batteries. Herein, a dual-shock chemical strategy has been developed to synthesize the carbon anode. This approach comprised two key phases: (1) a thermal shock utilizing ultrahigh temperature (3228 K) can thermodynamically facilitate graphitization; (2) a mechanical shock (21.64 MPa) disrupting the π-π interactions in the aromatic chains of carbon can result in hybrid-structured carbon composed of crystalline and amorphous carbon. The optimized carbon (DSC-200-0.3) demonstrates a capacity of 208.61 mAh/g at a 10C rate, with a significant enhancement comparing with 15 mAh/g of the original graphite. Impressively, it maintains 81.06% capacity even after 3000 charge-discharge cycles. Dynamic process analysis reveals that this superior rate performance is attributed to a larger interlayer spacing facilitating ion transport comparing with the original graphite, disordered amorphous carbon for additional lithium storage sites, and crystallized carbon for enhanced charge transfer. The dual-shock chemical approach offers a cost-effective and efficient method to rapidly produce hybrid-structured carbon anodes, enabling 10C fast charging capabilities in lithium-ion batteries.

Decline Mechanism of Graphite/Lithium Metal Hybrid Anode and Its Stabilization by Inorganic-Rich Solid Electrolyte Interface

The graphite/lithium metal hybrid anode shows great potential for achieving high-specific-energy lithium batteries. Despite the "dead lithium" problem caused by repeated stripping and deposition of Li component based on a conversion reaction, the degradation mechanism, based on intercalation reaction, of graphite in a hybrid anode is generally ignored. In this contribution, through in situ X-ray diffraction and in situ Raman analysis, we reveal that hysteresis and the mixed-phase state of graphite during deintercalation play a critical role in hybrid battery degradation. On the other hand, we successfully mitigated graphite degradation and increased the reversible capacity of the hybrid anode by introducing an inorganic-rich solid electrolyte interface. Remarkably, the hybrid anode (30% higher specific capacity compared to graphite) exhibits an average coulombic efficiency of 99.11% and retains 96.13% of initial capacity over 120 cycles. This work sheds new light on the advancement of high-specific-energy lithium secondary batteries.

Mathematical modelling of the conductivity in CZTiS-CZSnS as a function of synthesis temperature

The electrical behavior of photovoltaic materials related with Cu₂ZnTiS₄and Cu₂ZnSnS₄materials were analyzed as function of synthesis temperature in accordance with a new mathematical model based on the Kramers-Kronig equations with a high reliability. The samples were obtained through a hydrothermal route and a subsequent thermal treatment of solids at 550 °C for 1 h under nitrogen flow (50 ml min^-1). The characterization was done by x-ray diffraction, ultraviolet spectroscopy (UV), Raman spectroscopy, atomic force microscopy (AFM) and solid state impedance spectroscopy (IS) techniques. The structural characterization, confirm the obtention of a tetragonal material with spatial groupI-42m, oriented along (1 1 2) facet, with nanometric crystal sizes (5-6 nm). The AFM and Raman analysis confirm a high level of chemical homogeneity and correlation with the synthesis temperature, associated with the roughness of the samples. The UV spectroscopy confirm a band gap around 1.4-1.5 eV, evidencing the effectiveness of the synthesis process. The IS results at room temperature with a probability of 95%, confirm a high consistency of data with respect to values of real and imaginary impedance, allowing to obtain information of the conductance, reactance and inductance, achieving conductivity values around 10^-5and 10^-3Ω^-1 m^-1in comparison with traditional mathematical models used for this purpose.

Analysis of La4Ni3O10±δ-BaCe0.9Y0.1O3-δ Composite Cathodes for Proton Ceramic Fuel Cells

Layered Ruddlesden-Popper (RP) lanthanide nickelates, Lnn+1NinO3n+1 (Ln = La, Pr, and Nd; n = 1, 2, and 3) have generated great interest as potential cathodes for proton conducting fuel cells (PCFCs). The high-order phase (n = 3) is especially intriguing, as it possesses the property of a high and metallic-type electronic conductivity that persists to low temperatures. To provide the additional requirement of high ionic conductivity, a composite electrode is here suggested, formed by a combination of La4Ni3O10±δ with the proton conducting phase BaCe0.9Y0.1O3-δ (40 vol%). Electrochemical impedance spectroscopy (EIS) is used to analyse this composite electrode in both wet (pH2O ~ 10−2 atm) and low humidity (pH2O ~ 10−5 atm) conditions in an O2 atmosphere (400–550 °C). An extended analysis that first tests the stability of the impedance data through Kramers-Kronig and Bayesian Hilbert transform relations is outlined, that is subsequently complemented with the distribution function of relaxation times (DFRTs) methodology. In a final step, correction of the impedance data against the short-circuiting contribution from the electrolyte substrate is also performed. This work offers a detailed assessment of the La4Ni3O10±δ-BaCe0.9Y0.1O3-δ composite cathode, while providing a robust analysis methodology for other researchers working on the development of electrodes for PCFCs.

A Fusion Parameter Method for Classifying Freshness of Fish Based on Electrochemical Impedance Spectroscopy

Compared with using a single characteristic parameter of electrochemical impedance spectroscopy (EIS) to classify the freshness of fish samples from different origins, more characteristic parameters could bring higher accuracy as well as complexity, subjectivity, and uncertainty. In order to eliminate the disadvantages of the multiparameter model, a data fusion method based on model similarity (DFMS) was proposed in this study. The similarity relation between the freshness models based on EIS characteristic parameters and physicochemical indicator was analyzed and quantified accordingly, and then, the weighting factors of the fusion model were determined. The classification accuracy rate of fish freshness based on DFMS was 9.2∼15% greater than that of a single EIS characteristic parameter. The novel dimensionless fusion parameter method proposed in this article might provide a simple yet effective indicator for EIS-based food quality evaluation.