Dynamic Electrochemical Impedance Spectroscopy Technique Research Articles

Lithium plating detection using dynamic electrochemical impedance spectroscopy in lithium-ion batteries

This paper proposes a lithium plating detection method for lithium-ion batteries that can be applied in real time, during the charging procedure. It is based on the impedance analysis and it can be realized by utilizing the dynamic electrochemical impedance spectroscopy (DEIS) technique. Specifically, a sinusoidal current is superimposed on the charging current, and the battery impedance is analyzed in the frequency domain without interrupting the charging procedure. In case of lithium plating during charging, the graphite interfacial impedance is significantly decreased and thus, the lithium plating can be detected by monitoring the real and imaginary parts of the battery impedance in real-time. Two battery cell types with different active materials and energy densities are examined at several temperatures and charging currents. The effectiveness of the proposed DEIS technique is validated with the voltage relaxation profile method and in comparison with the current interruption method, for different charging conditions, cell formats and chemistries. The experimental results reveal that the proposed method is capable to effectively detect the lithium plating for rates as high as 6C, at different temperatures and for different battery types. • Nondestructive method to detect the onset of lithium plating during charging • Dynamic EIS applied in real-time without interrupting the charging procedure • Lithium plating is detected by monitoring the battery interfacial impedance • Battery operating conditions are considered at the lithium plating detection • Experimental validation and correlation with existing methods

Synergy between partially exfoliated carbon nanotubes-sulfur cathode and nitrogen rich dual function interlayer for high performance lithium sulfur battery

Confinement of lithium polysulfides (LPS) within the cathode is one of the major challenges of LithiumSulfur Batteries (LiS), which hinders its practical application. Herein, a simple strategy is demonstrated to reduce the dissolution of LPS by graphitic carbon nitride nanosheets (GCN) supported by a gas diffusion layer (GDL), which consists of high nitrogen content, acts as polar sites for LPS adsorption. The partially exfoliated multi-walled carbon nanotube is used as a sulfur host (PECNT/S), which accommodates the high amount of sulfur loading due to its high specific surface area and pore volume. PECNT/S/GCN-GDL cathode remarkably exhibits excellent cyclic stability at 1C with 92.2% of initial capacity retention even after 500 cycles due to the strong trapping of LPS by chemisorption on GCN while the electrically conducting GDL ropes the electron conduction as well as electrolyte and Li+ ion diffusion. Dynamic electrochemical impedance spectroscopy technique further provides the understanding of confinement of LPS on the resultant PECNT/S/GCN-GDL electrode during charge-discharge processes. In addition, the importance of the upper potential limits has been studied in this work. Our study thus addresses many challenges of the LiS batteries by the use of carbon-based nanomaterials.

Impedance Measurement and Selection of Electrochemical Equivalent Circuit of a Working PEM Fuel Cell Cathode

The dynamic impedance analysis of direct methanol fuel cell (DMFC) cathode supplied with pure oxygen is presented. Presented results were obtained during dynamic changes of the current density in working fuel cell. Investigation of the occurring processes at cathode was carried with dynamic electrochemical impedance spectroscopy (DEIS). A discussion was conducted based on the determined correlation parameter χ2. It was shown that the selection of an appropriate equivalent circuit cannot be carried out only with correlation parameter of analysis between experimental impedance spectra and the equivalent circuit. Comprehensive analysis of equivalent circuit parameter changes during fuel cell working is needed to determine appropriate equivalent model. Thanks to DEIS technique, comparing of the different equivalent circuits proposed in other works during dynamic changes of operating condition could be presented. In addition, the new electrical circuit has been proposed to describe the cathode performance with poisoned electrocatalyst in fuel cell with reduced efficiency.Graphical The equivalent electrical circuit of an operating fuel cell cathode

Study on surface termination of boron-doped diamond electrodes under anodic polarization in H2SO4 by means of dynamic impedance technique

Anodic oxidation is a popular way to modify termination bonds at boron doped diamond electrodes altering their electrochemical and physicochemical properties. Our studies, performed with dynamic electrochemical impedance spectroscopy technique, supported with X-ray photoelectron spectroscopy and ellipsometry analysis prove its utility in continuous on-line monitoring of impedance changes on the electrode surface under polarization conditions, which may be of great use for the optimization of working conditions of the process. Based on our results, it can be observed that oxidation of termination bonds is a multistep process, each stage initiated at different anodic polarization potential. The factors influencing oxidation of termination bonds are presented and discussed. It was also possible to draw a conclusion about the removal of sp2 carbon impurities from the electrode surface as a precondition to activate the oxidation process. The depth and time of polarization, boron uptake at the grain boundaries, as well as crystallographic orientation of individual grains influence the heterogeneity of the oxidation process. Its partial reversibility was observed as a result of cathodic polarization in the range of hydrogen evolution, however due to irreversible corrosion of sp2 impurities, hydrogenation is not complete. This form of hydrogenation additionally contaminates the electrode surface with sulphur.

Instantaneous impedance evaluation of dissolution of AISI 304 stainless steel during intergranular corrosion

PurposeThe purpose of this paper is to focus on diversification between electrical parameters determined on the basis of instantaneous impedance measurements within the activation and reactivation scan of dissolution of sensitized AISI 304 stainless steel during a proceeding intergranular corrosion process.Design/methodology/approachThe investigations were carried out by means of dynamic electrochemical impedance spectroscopy (DEIS). DEIS measurements were conducted “on‐line” while the samples were polarized in agreement with a measurement procedure presented in the ASTM G108‐94 standard, in order to guarantee conditions equivalent with the DL‐EPR tests performed on AISI 304 stainless steel.FindingsPerformed researches revealed the advantages of the DEIS technique over standard double‐loop electrochemical potentiokinetic reactivation (DL‐EPR) tests in the field of intergranular corrosion investigations. Application of the DEIS technique made it possible to trace instantaneous changes in the examined system's impedance versus potential during the intergranular corrosion process. The form of recorded DEIS spectra and obtained distribution of measurement frequencies within the reactivation potential range were equivalent to those obtained for pure iron dissolution in sulfuric acid medium. As a result, instantaneous changes of electrical double layer capacitance and charge transfer resistance as a function of potential have been obtained in the range of activation and reactivation scans.Originality/valueThe paper provides information regarding diversification between the electrical double layer capacitance and the charge transfer resistance determined for sensitized AISI 304 stainless steel with respect to polarization conditions during the standard DL‐EPR test, which were obtained in order to evaluate the susceptibility to intergranular corrosion.

Electrochemical characterization of Prussian blue type nickel hexacyanoferrate redox mediator for potential application as charge relay in dye-sensitized solar cells

A polynuclear electronically/ionically (redox) conducting mixed-valent inorganic material such as nickel(II) hexacyanoferrate(II,III), NiHCF, was considered for potential application as a redox mediator (charge relay) in dye-sensitized solar cell (DSSC). The NiHCF redox reactions were found fast and reversible not only when the system was studied as thin film exposed to an aqueous supporting electrolyte but also as bulk material (pasted powder) in solid state, i.e., in the absence of contact with external liquid electrolyte phase. Usefulness of NiHCF material was diagnosed using conventional electroanalytical approaches, solid-state voltammetric methodology, as well as the dynamic electrochemical impedance spectroscopy technique that permitted monitoring of impedance spectra under potentiodynamic conditions. The material was utilized in a mixed-valent state, i.e., as a mixture of K4NiII[FeII(CN)6] and K3NiII[FeIII(CN)6] in which iron(II) and iron(III) sites were at the 1:1 ratio. Under such conditions, dynamics of electron-hopping between mixed-valent iron sites was maximized. Our DSSC utilized cis–dithiocyanoatobis(4,4′-dicarboxylic acid-2,2′-bipyridine) ruthenium(II) dye (N3) adsorbed onto TiO2 semiconductor and NiHCF as redox mediator. Although performance of our DSSC was not optimized in terms of the NiHCF film thickness and morphology, as well as lower photocurrents in comparison to those characteristic of the iodine/iodide based DSSC were obtained, our system yielded readily fairly high open-circuit photovoltages on the level of 800 mV. An important issue was that the formal potential of NiHCF was more positive relative to the potential of the iodide/triiodide couple while being still more negative than that equivalent to the ground state of the N3 dye. Thus, NiHCF mediator was able to regenerate the dye.

Investigation effect of benzotriazole on the corrosion of brass-MM55 alloy in artificial seawater by dynamic EIS

The electrochemical behavior of brass-MM55 alloy was studied in artificial seawater with benzotriazole by using a novel method called dynamic electrochemical impedance spectroscopy (DEIS). This method gives possibility to investigate the protection of metals in corrosive medium by using inhibitors in galvanostatic conditions for a long time. Instantaneous impedance spectra for brass-MM55 were recorded for 10 h in artificial seawater for different concentration of benzotriazole. It was found that a few hours were not enough for the accurate calculation of corrosion inhibition. Also with this method it is possible to figure out how the charge transfer resistance (R ct) changes by the time. Usefulness of the DEIS technique in the investigation of non-stationary phenomena has been proved in the field of inhibitor research. All studies clearly show that benzotriazole inhibits the corrosion of brass-MM55 alloy in artificial seawater solution and the value of inhibition efficiency increases with increasing concentration of benzotriazole.

Evaluation of corrosion inhibition of brass-118 in artificial seawater by benzotriazole using Dynamic EIS

The paper presents the results of corrosion behaviour of brass-118 in artificial seawater and the inhibitor effect of benzotriazole (BTA) by using a novel method called dynamic electrochemical impedance spectroscopy (DEIS). This method allows the tracing of the dynamics of the corrosion and the inhibition process based on the evaluation of electrical parameters of the equivalent circuit. Instantaneous impedance spectra recorded up to 10 h show that an exposure of few hours is not enough for the determination of inhibition efficiency. The results indicate the usefulness of DEIS technique in the field of inhibitor research.

DEIS evaluation of the relative effective surface area of AISI 304 stainless steel dissolution process in conditions of intergranular corrosion

The results presented in this paper contribute further information concerning examinations of AISI 304 stainless steel dissolution process in conditions of proceeding intergranular corrosion (IG) which have been determined on the basis of dynamic electrochemical impedance spectroscopy (DEIS) measurements. For the first time changes of the relative effective surface area versus time of AISI 304 stainless steel dissolution process in conditions of proceeding intergranular corrosion (IG) in 0.5 M H 2SO 4 + 0.01 M KSCN solution within the range of reactivation polarization scan have been demonstrated. The assessment of the effective surface area of the investigated process was based on approximation to theory of iron dissolution in sulfuric acid medium according to the shape of instantaneous impedance spectra recorded by means of DEIS technique. As a result, it was possible to evaluate that initially changes of the employed equivalent circuit parameters are not only caused by the changes of the relative effective surface area but also by the changes of the AISI 304 SS dissolution process kinetics. Further progress of the examined process implied that changes of the equivalent circuit parameters are only affected by the changes of the relative effective surface area during proceeding IG. Moreover, it was found that the character of changes of the relative effective surface area in conditions of proceeding IG can be described by exponential function.

Impact of sensitization on dissolution process of AISI 304 stainless steel during intergranular corrosion evaluated using DEIS technique

The paper presents the results of instantaneous impedance changes measurements vs. reactivation potential performed by means of dynamic electrochemical impedance spectroscopy (DEIS) technique for AISI 304 stainless steel (SS) dissolution process during intergranular corrosion (IG) in 0.5 M H2SO4 + 0.01 M KSCN solution. With the use of DEIS method, it was possible to estimate dynamic changes of the examined system’s impedance in conditions of proceeding IG process. Furthermore, the paper proposes an alternative way of evaluating AISI 304 stainless steel dissolution rate during intergranular corrosion based on approximation to theory of iron dissolution in sulfuric acid medium. Simultaneously, based on the DEIS measurements, information about the degree of sensitization of the examined material were obtained. Performed research revealed the advantages of the DEIS technique over the classical double-loop electrochemical potentiokinetic reactivation tests when investigating intergranular corrosion process.

Impedance Monitoring of Carbon Steel Cavitation Erosion under the Influence of Corrosive Factors

The degradation of carbon mild steel under cavitation erosion–corrosion exposure was studied by means of a 20 kHz ultrasonic device with a piezoelectric inducer. Possibilities of estimation of material failure by current measurement techniques are presented and discussed. The effect of cavitation exposure of the mild steel has been investigated in situ with the dynamic electrochemical impedance spectroscopy technique. Estimation of the surface degradation rate is enabled by an adequate equivalent circuit selection. A dynamic impedance method was used to verify the impedance parameters online during the measurement. These measurements are assisted by estimation of the weight loss function commonly used for the evaluation of erosion–corrosion resistance of materials.

DEIS assessment of AISI 304 stainless steel dissolution process in conditions of intergranular corrosion

Results presented in this paper are first that demonstrate instantaneous impedance changes versus reactivation potential detected by means of dynamic electrochemical impedance spectroscopy (DEIS) technique for AISI 304 stainless steel dissolution process proceeding during intergranular corrosion (IG) in 0.5 M SO 4 2− + 0.01 M KSCN solution of different pHs. Application of DEIS method made it possible to evaluate dynamic changes of the examined system's impedance in conditions of IG. As a result, controlling stage of the overall rate of AISI 304 SS dissolution process was determined. Moreover, the paper proposes an alternative way of assessment of AISI 304 SS dissolution rate during intergranular corrosion based on approximation to theory of iron dissolution in sulfuric acid medium. Simultaneously, on the basis of the DEIS measurements it was possible to obtain information about the degree of sensitization (DOS) of the examined material. Accordingly, performed researches revealed the advantage of the DEIS technique over the electrochemical potentiokinetic reactivation (EPR) tests when investigating intergranular corrosion process.

Application of the dynamic EIS to investigation of transport within organic coatings

The paper presents results of an investigation on rapid degradation of organic coating using a novel method called dynamic electrochemical impedance spectroscopy (DEIS). For 60 s, polyvinyl coating has been subjected to the impact of 0.01 M solution of tetraethylammonium tetrafluoroborate in methylene chloride. During that time instantaneous impedance spectra have been determined allowing tracing the dynamics of a degradation process. Usefulness of the DEIS technique in the investigation of non-stationary phenomena has been proved in the field of coating research.

Detection of stress corrosion cracking dynamics by dynamic electrochemical impedance spectroscopy

A novel dynamic electrochemical impedance spectroscopy (DEIS) technique has been developed that offers the possibility to determine impedance characteristics in a time domain during the rupture of the protective passive layer. This ability is associated with the analysis methodologyof the technique, which enables selective time–frequency analysis of the measurement data. This paper proposes that the DEIS technique allows the acquisition of instantaneous changes during the passive layer cracking process, which is strongly related to the initiation stage of stresscorrosion cracking. Moreover, the principles of application of the novel method in such investigations are discussed.