Chapter Four · failure evidence
What Electrochemical Impedance Spectroscopy (EIS) got wrong, from 30 dissertations
Across the analyzed thesis records, electrochemical impedance spectroscopy investigations frequently encountered difficulties related to equivalent circuit overparameterization and cell geometry artifacts. Measurements were also compromised by adverse electrolyte environments, microelectrode degradation, and high-frequency instrumentation distortions. These records come from PhD theses at 16 institutions, 2021 to 2026. Each links to its thesis. They were extracted by language models reading the full text, so treat each as a lead to read, not a verdict.
Equivalent circuit models fail due to overparameterization and inadequate representation of physical interfaces
Fitting impedance data with excessive circuit elements led to severe overparameterization, parameter uncertainties, and non-unique models without physical meaning. Simpler resistive or ideal capacitive models also failed by neglecting crucial physical effects such as surface roughness, cellular infiltration, and porous layer diffusion.
Tried and failed
two constant phase element equivalent circuit modeling applied to impedance spectroscopy of functionalized semiconductor interfaces. Outcome: overfit. Reason: overparameterization caused overfitting and obscured the physical interpretation of chemical capacitance
Electronic structure and photoelectrochemistry of Si(111) functionalized by acene derivatives · UT Austin
Tried and failed
adding circuit elements to equivalent circuit model applied to electrochemical impedance spectroscopy fitting. Outcome: overfit. Reason: increased discrepancies and parameter fitting uncertainties due to model overparameterization
Considered and rejected
Considered and rejected: Rejected impedance spectroscopy equivalent circuit curve fitting because the circuit models are typically non-unique and parameters are not scientifically meaningful.
Electric Polarization in Electronic Conductors · DSpace at SUNY Buffalo
Considered and rejected
Considered and rejected: Purely resistive Marker 1 impedance evaluation was rejected for in vivo FBR monitoring due to high low-frequency capacitance from cellular infiltration, requiring an equivalent circuit model.
Considered and rejected
Considered and rejected: Rejected the Randles equivalent circuit (Circuit 1) and active corrosion model (Circuit 2) for EIS fitting of Cu in [C4C1im]Cl, adopting Circuit 4 (porous layer with Warburg impedance) instead
Considered and rejected
Considered and rejected: Rejected modeling composite cathode local impedance using an ideal double-layer capacitor in favor of a constant phase element (CPE) to account for surface roughness.
Charakterisierung des Festelektrolytsystems (1−x) Li3PS4 + x LiI sowie dessen Anwendung in Lithiumionen-Festkörperbatterien Characterization of the solid electrolyte system (1-x) Li3PS4 + x LiI and its application in lithium ion all-solid-state batteries · open_UMR Marburg DSpace 10.0
Cell geometry and counter electrode interactions distort spectra and obscure targeted impedances
Electrode overhang and excessive cell spacing produced erratic spectra or concealed low-frequency diffusion arcs. In addition, degradation and solid electrolyte interphase growth on counter or reference electrodes introduced crosstalk that confounded the isolation of working electrode impedances.
Tried and failed
electrochemical impedance spectroscopy applied to single-layer pouch cells. Outcome: unstable. Reason: extreme electrode overhang and long diffusion pathways caused erratic, non-repeatable spectra
Considered and rejected
Considered and rejected: Rejected standard electrochemical reference electrodes as unreliable for isolating cathode impedances in these solid oxide cells.
Investigation and Improvement of SofC Composite Cathodes · Penn
Considered and rejected
Considered and rejected: Rejected analyzing fluorinated electrolytes (HFEs) using LTO full cells in GEIS due to severe SEI growth from FEC on the LTO anode confounding cathode impedance measurements.
Considered and rejected
Considered and rejected: Rejected using metallic Li counter electrodes for long-term isolated evaluation of positive electrode materials due to severe solvent degradation and crosstalk inducing CEI impedance growth.
Understanding degradation in lithium-ion and lithium-air batteries · University of Nottingham Repository
Considered and rejected
Considered and rejected: Rejected using a 1 mm thick EPDM sealing ring for transference number measurements despite good margin sealing, because it enforces an electrode distance >0.5 mm which obscures the low-frequency electrolyte diffusion arc.
Adverse testing environments and electrolyte conditions mask electrochemical features
Low electrolyte conductivity, oxygen diffusion, and amino acid solvents generated noise or excessively high charge transfer resistance that obscured Nyquist plots. Furthermore, liquid immersion artifacts and open-circuit fields in asymmetric pH electrolytes obscured membrane responses and early depletion layer formation.
Tried and failed
electrochemical impedance spectroscopy for corrosion rate measurement applied to steel alloys in amino acid solvents. Outcome: no signal. Reason: low-frequency noise and lack of semicircular response prevented polarization resistance fitting
Capture of CO₂ Using Potassium Salts of Amino Acids and Guanidine-Based Ligands · Georgia Tech
Tried and failed
electrochemical impedance spectroscopy in low conductivity media applied to oxide layer characterization in tap water. Outcome: no signal. Reason: insufficient fluid conductivity and oxygen diffusion effects caused excessively high charge transfer resistance, obscuring Nyquist plots
The application of electrolytic in-process dressing to precision grinding processes · Cranfield
Considered and rejected
Considered and rejected: Rejected using asymmetric pH electrolytes for EIS depletion region characterization because intrinsic open-circuit electric fields obscure early depletion layer formation.
Ion Management And Mass Transport For (photo-) Electrochemical Conversions · Penn
Tried and failed
Electrochemical impedance spectroscopy in liquid aqueous environment applied to ultra-thin freestanding ceramic membranes. Reason: Liquid immersion produced severe measurement artifacts, requiring testing in humidified gas instead
Microelectrode systems suffer from fabrication defects, buffer saturation, and probe burnout
Microgap interdigitated electrodes exhibited shorting defects and unrepeatable spectra at narrow spacings. Standard redox probe concentrations caused microscale electrode burnout, while high ionic buffer conductivity caused electrical saturation that masked target binding signals.
Tried and failed
Non-faradaic impedance spectroscopy on microgap interdigitated electrodes applied to bacterial cell detection. Outcome: unstable. Reason: High microfabrication shorting defects and unrepeatable impedance spectra at small interelectrode spacings
The impact of mass transport and surface charging on the performance of field effect transistor biosensors · Georgia Tech
Tried and failed
impedance biosensing with interdigitated electrodes applied to biomolecule detection in ionic buffer. Outcome: no signal. Reason: ionic buffer conductivity caused electrical saturation, masking impedance changes from binding
Capillary-driven Microfluidic Biosensing Platforms for Digital Biomolecule Detection · Texas Tech
Tried and failed
electrochemical impedance spectroscopy with standard redox probe applied to thin-film interdigitated microelectrodes. Outcome: unstable. Reason: standard 10 mM ferricyanide/ferrocyanide concentration caused electrical burnout and degradation of microscale working electrodes
Development of nanomip based sensors for drugs of abuse detection. · Cranfield
Instrumental artifacts and overlapping relaxation timescales corrupt high-frequency impedance extraction
Multi-electrode setups and measurement cables suffered from high-frequency crosstalk and pseudo-inductive artifacts that produced non-physical negative resistance values. In nanocrystalline hydrated films, overlapping relaxation timescales from structural gradients prevented the separation of individual semicircles.
Tried and failed
electrochemical impedance spectroscopy to extract ionic conductivity applied to nanocrystalline hydrated thin films. Reason: multiple overlapping semicircles with similar RC timescales caused by nanocrystallinity and hydration gradients
Proton dynamics in ultrathin GdO𝑥H𝑦 films for magneto-ionics · MIT
Tried and failed
simple standard RC equivalent circuit model fitting applied to electrochemical impedance spectroscopy data. Reason: high-frequency pseudo-inductive cable artefacts produced non-physical negative resistance values
Organic electrochemical transistors with PVA hydrogels/PEDOT:PSS channel · Imperial
Tried and failed
multi-electrode dielectric impedance spectroscopy applied to in-line fluid flow monitoring. Reason: inter-electrode cross-talk at specific high frequencies severely distorted impedance measurements
Left open by the authors
Problems the authors named and did not get to.
Left open
Investigate the impact of battery State-of-Health degradation and SEI growth on impedance phase-based temperature estimation. Blocker: Requires conducting physical battery cycling and degradation experiments with electrochemical impedance spectroscopy instrumentation
Abuse detection in Li-ion batteries using Electrochemical Impedance Spectroscopy · EPFL
Left open
Isolate the individual influences of ionic conductivity, redox mediator kinetics, Li2O2 reaction kinetics, and mass transport on charge overpotential. Blocker: Requires a wet chemistry and electrochemistry laboratory to synthesize electrolytes and measure kinetics and overpotentials in battery cells.
Towards comprehensive design of electrolytes for electrochemical energy storage · MIT
Left open
Investigate dissolved transition metal effects, like Fe species, on SEI growth and impedance in lithium-ion batteries using operando spectroscopy. Blocker: Requires a physical electrochemical laboratory with operando soft X-ray spectroscopy apparatus and battery assembly equipment
Left open
Investigate timescales and resistances of charge transfer, desolvation, and SEI polarization across different salt anions in battery electrolytes. Blocker: Requires wet lab electrochemical testing, electrolyte preparation, and impedance spectroscopy equipment.
Structural engineering of lithium-ion battery electrodes for the production of stable, energy-dense storage · UT Austin
Left open
Apply electrochemical impedance spectroscopy (EIS) to estimate health and predict remaining useful life at the battery module or pack level. Blocker: Requires a physical battery module/pack setup and EIS hardware to collect experimental pack-level impedance data.
Lithium-Ion Battery State of Health Estimation and Remaining Useful Life Prediction: Practical Techniques for Varied Operating Conditions · Scholarship at UWindsor Institutional Repository
Left open
Optimize electrochemical generation of superoxide radical stock solutions using varied electrode materials, O2-saturated electrolytes, and higher reaction voltages. Blocker: Requires an electrochemistry wet lab, electrode materials, chemical reagents, and physical measurement apparatus.
Left open
Investigate heterogeneous electrochemical and chemo-mechanical degradation at cathode-electrolyte interfaces using in-operando X-ray fluorescence microscopy combined with X-ray absorption spectroscopy. Blocker: Requires synchrotron beamline facilities, specialized in-operando XFM/XAS instrumentation, and physical thin-film solid-state battery samples.
Left open
Model pulse charging and current harmonics using EIS battery models and develop an EIS-based charging protocol optimization methodology. Blocker: Requires battery testing apparatus and electrochemical impedance spectroscopy (EIS) hardware to evaluate pulse charging effects.
Lithium-Ion Battery State of Health Estimation and Remaining Useful Life Prediction: Practical Techniques for Varied Operating Conditions · Scholarship at UWindsor Institutional Repository
Left open
Elucidate the elementary reaction steps determining how electrolytes influence sulfur redox near the end of discharge in Li-SF6 batteries. Blocker: Requires wet-lab electrochemical testing and specialized battery diagnostic apparatus.
Tailoring Fluoride/Fluorine Bond Activity for High-Energy Li and Li-ion Batteries · MIT
Left open
Elucidate specific ion-ion interactions determining the open-circuit voltage inflection point beyond ~0.4 M KCl in mixed-electrolyte bipolar membranes. Blocker: Requires experimental wet-lab electrochemical testing and mixed-electrolyte bipolar membrane characterization apparatus.
Membrane-Electrolyte System Studies for Aqueous Redox Flow Reactors · Harvard
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