Search Results (11)

We present a time-domain direct current (DC) approach to differentiate positive- (PE) and negative-electrode (NE) contributions from two-electrode full-cell signals in lithium-ion batteries, enabling electrode-resolved diagnostics without specialized instrumentation. The responses of a LiNi_0.8Co_0.1Mn_0.1O₂ (PE)/graphite (NE) cell were recorded across −20 to 20 °C during galvanostatic pulses and subsequent open-circuit relaxations, alongside electrochemical impedance spectroscopy (EIS) measurements. These responses were analyzed using an equivalent-circuit-based model to decompose them into terms with characteristic times. Their distinct temperature dependences enabled attribution of the dominant terms to PE or NE, especially at low temperatures where temporal separation is substantial. The electrode attribution and activation energies were cross-validated against three-electrode measurements and were consistent with EIS-derived time constants. Reconstructing full-cell voltage transients from the identified terms reproduced the measured electrode-specific behavior, and quantitative comparisons showed that the DC time-domain separation aligned closely with directly measured PE/NE overpotentials during the current pulse. These results demonstrate a practical pathway to extract electrode-resolved information from cell voltage alone, offering new methodological possibilities for battery diagnostics and management while complementing three-electrode and alternating current (AC) techniques that are often constrained in field applications. Full article

Conventional applications of the Galvanostatic Intermittent Titration Technique (GITT) and EIS for estimating chemical diffusivity in battery electrodes face issues such as insufficient relaxation time to reach equilibrium, excessively long pulse durations that violate the short-time diffusion assumption, and the assumption of sequential electrode reaction and diffusion processes. In this work, a quasi-equilibrium criterion of 0.1 mV h⁻¹ was applied to NMC622 electrodes, yielding 8–9 h relaxations below 3.8 V, but above 3.8 V, voltage decayed linearly and indefinitely, even upon discharging titration, showing unusual nonmonotonic relaxation behavior. The initial 36-s transients of a 10-min galvanostatic pulse and diffusion impedance in series with the electrode reaction yielded consistent diffusivity values. However, solid-state diffusion in spherical active particles within porous electrodes, where ambipolar diffusion occurs in the pore electrolyte with $t_{+}=0.3$, requires a physics-based three-rail transmission line model (TLM). The corrected diffusivity may be three to four times higher. An analytic two-rail TLM approximating the three-rail numerical model was applied to temperature- and frequency-dependent EIS data. This approach mitigates parameter ambiguity and unphysical correlations in EIS. Physics-based EIS enables the identification of multistep energetics and the diagnosis of performance and degradation mechanisms. Full article

The need for alternative energy storage options beyond lithium-ion batteries is critical due to their high costs, resource scarcity, and environmental concerns. Zinc-ion batteries offer a promising solution, given zinc’s abundance, cost effectiveness, and safety, particularly its compatibility with non-flammable aqueous electrolytes. In this study, the potential of laser-ablation-based titanium oxide as a novel cathode material for zinc-ion batteries was investigated. The ultra-short laser pulses for in situ nanostructure generation (ULPING) technique was employed to generate nanostructured titanium oxide. This laser ablation process produced highly porous nanostructures, enhancing the electrochemical performance of the electrodes. Zinc and titanium oxide samples were evaluated using two-electrode and three-electrode setups, with cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge (GCD) techniques. Optimal cathode materials were identified in the Ti-5W (laser ablated twice) and Ti-10W (laser ablated ten times) samples, which demonstrated excellent charge capacity and energy density. The Ti-10W sample exhibited superior long-term performance due to its highly porous nanostructures, improving ion diffusion and electron transport. The potential of laser-ablated titanium oxide as a high-performance cathode material for zinc-ion batteries was highlighted, emphasizing the importance of further research to optimize laser parameters and enhance the stability and scalability of these electrodes. Full article

Introduction. Modern medicine depends on biomaterials. Thus, it is imperative that these materials continue to be developed and improved. Methods. This work aimed at designing hydroxyapatite-based coatings (HAp) with high osseointegration properties by developing a biomimetic morphology that resembles that of natural HAp found in bone tissue. The biomimetic HAp coatings with plate-like morphology were successfully obtained using the pulsed galvanostatic electrochemical approach on pure Ti discs. The coatings were investigated in terms of surface morphology, chemical and phasic composition, in vitro bioactivity, and cell interaction. Results and Discussion. The morphological investigations revealed that using electrochemical deposition, HAp-based coatings with very thin and wide plate-like crystals can be obtained. The chemical composition highlighted that both Ca and P are present, and that the Ca/P ratio registered values of 1.66, being close to that of the stoichiometric HAp of 1.67. The phasic composition analysis showed that the main phase consisted of hydroxyapatite (ICDD #09-0432), with a crystallinity of ~25%. The biomineralization ability of the cp-Ti substrate was improved by the HAp-based coatings, reaching a maximum value of 9.7 mg after 3 weeks of immersion in simulated body fluid (SBF) compared to the Ti samples which gained a mass of only 0.3 mg after the same period. The in vitro experiments using human mesenchymal stem cells demonstrated that the HAp-based coatings enhanced the extracellular matrix, the intracellular deposition of Ca, and cell viability when compared to the cp-Ti substrate, demonstrating the advantages of the developed coatings. Conclusions. Therefore, the outcomes confirm that coatings with improved and adjustable properties can be designed for medical applications by using the electrochemical deposition technique. Full article

The corrosion of steel in reinforced concrete exposed to marine environments or winter de-icing poses a significant threat. However, evaluation of it is challenging due to variables such as environmental conditions and concrete properties. Many studies in concrete engineering have introduced a performance-based approach, evaluating structures with experimental data by considering the environmental conditions. Electrochemical techniques, including half-cell potential (HP), electrochemical impedance spectroscopy (EIS), and galvanostatic pulse (GP), are widely used for studying steel corrosion in concrete. Despite the widespread use, corrosion measurements have still limitations due to ambiguous impedance results from concrete presence, equipment sensitivity, and analysis flexibility. The corrosion of steel in chloride-laden concrete was assessed in well-controlled laboratory conditions using EIS and GP before field application. The results showed that measured values for corrosion parameters were consistent with each other (within 10% discrepancy). Corrosion initiation times varied from 171 to 319 days depending on the techniques, the differences attributed to measurement periods, and the condition of the steel. In addition, it was confirmed that the corrosion potential for HP was significantly correlated with the time constant for GP. This study demonstrated these techniques to improve both the understanding of the corrosion process and the accuracy of the calculated corrosion rate. Full article

The aim of this research was to obtain hydroxyapatite (HAp)-based coatings doped with different concentrations of Mg on a Ti nanostructured surface through electrochemical techniques and to evaluate the influence of Mg content on the properties of HAp. The undoped and doped HAp-based coatings were electrochemically deposited in galvanostatic pulsed mode on titania nanotubes with a diameter of ~72 nm, being designed to enhance the adhesion of the HAp coatings to the Ti substrate. The obtained materials were investigated by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), and Fourier-Transform Infra-Red spectroscopy (FTIR). The adhesion of the coatings to the substrate was also evaluated with the help of the “tape-test” and the micro-scratch test. The morphology (SEM) of all the coatings is made of very thin and narrow ribbon-like crystals, with some alterations with respect to the Mg amount in the coatings. Thus, a concentration of 1 mM of Mg in the electrolyte leads to wider and thicker ribbon-like crystals, while a concentration of 1.5 mM in the electrolyte generated a morphology that resembles the undoped HAp. Both phase composition (XRD) and chemical bonds (FTIR) analysis proved the formation of HAp in all coatings. Moreover, according to XRD, all coatings have a strong orientation toward the (002) plane. Irrespective of the Mg content, all coatings registered an average roughness between approx. 500 and 600 nm, while the coating thickness increased after addition of Mg, from a value of 9.6 μm, for the undoped HAp, to 11.3 μm and ~13.7 μm for H/Mg1 and H/Mg2, respectively. In terms of adhesion, it was shown that the coatings a H/Mg2 had a poorer adhesion when compared to H/Mg1 and the undoped HAp (H), which registered similar adhesion, indicating that a concentration of 1.5 mM of Mg in the electrolyte reduces the adhesion of the Hap-based coatings to the nanostructured surface. The obtained results indicated that Mg concentrations up to 1 mM in the electrolyte can enhance the properties of HAp-based coatings electrochemically deposited on a nanostructured surface, while even a slightly higher concentration of 1.5 mM can negatively impact the characteristics of HAp coatings. Full article

Hydroxyapatite (HAp) is the most widely used calcium phosphate as a coating on metal implants due to its biocompatibility and bioactivity. The aim of this research is to evaluate the effect of the pH’s electrolyte and doping element on the morphology, roughness, chemical, and phasic composition of hydroxyapatite-based coatings obtained by pulsed galvanostatic electrochemical deposition. As doping elements, both Sr and Ag were selected due to their good osseoinductive character and antibacterial effect, respectively. The electrolytes were prepared at pH 4 and 5, in which specific concentrations of Sr, Ag, and Sr + Ag were added. In terms of morphology, all coatings consist in ribbon-like crystals, which at pH 5 appear to be a little larger. Addition of Sr did not affect the morphology of HAp, while Ag addition has led to the formation of flower-like crystals agglomeration. When both doping elements were added, the flowers like agglomerations caused by the Ag have diminished, indicating the competition between Sr and Ag. X-Ray Diffraction analysis has highlighted that Sr and/or Ag have successfully substituted the Ca in the HAp structure. Moreover, at higher pH, the crystallinity of all HAp coatings was enhanced. Thus, it can be said that the electrolyte’s pH enhances to some extent the properties of HAp-based coatings, while the addition of Sr and/or Ag does not negatively impact the obtained features of HAp, indicating that by using pulsed galvanostatic electrochemical deposition, materials with tunable features dictated by the function of the coated medical device can be designed. Full article

The concrete cover is the basic protection of the reinforcement against the influence of external factors that may lead to its corrosion. Its effectiveness depends mainly on the composition of the concrete mix, including the cement used. Depending on external environmental factors that may aggressively affect the structure, various types of cements and concrete admixtures are recommended. The paper presents the results of tests that allow us to assess the effect of the type of cement used and the air-entraining agent on the effectiveness of the concrete cover as a layer protecting the reinforcement against corrosion. In order to initiate the corrosion process, the reinforced concrete specimens were subjected to cycles of freezing and thawing in a sodium chloride solution. The degree of advancement of the corrosion process was investigated using the electrochemical galvanostatic pulse technique. Additionally, the microstructure of specimens taken from the cover was observed under a scanning electron microscope. The research has shown that in the situation of simultaneous action of chloride ions and freezing cycles, in order to effectively protect the reinforcement against corrosion, the application of both blast-furnace slag cement and an air-entraining agent performed the best. Full article

We report a photonic technique to instantaneously synthesize cobalt oxide reduced graphitic oxide (CoO_x-rGO) supercapacitor electrodes. The electrode processing is achieved through rapidly heating the precursor material by irradiation of high-energy pulsed mostly visible light from a xenon lamp. Due to the short duration of the light pulse, we prepared the electrodes at room temperature instantaneously (ms), thus eliminating the several hours of processing times of the conventional techniques. The as-prepared electrodes exhibited a highly porous morphology, allowing for enhanced ionic transport during electrochemical interactions. The electrochemical properties of the CoO_x-rGO electrodes were studied in 1 M KOH aqueous electrolyte. The non-rectangular cyclic voltammetry (CV) curves with characteristic redox peaks indicated the pseudocapacitive charge storage mechanism of the electrodes. From the discharge curves at 0.4 mA/cm² and 1.6 A/g constant current densities, the electrode showed areal specific capacitance of 17 mF/cm² and specific capacitance of 69 F/g, respectively. Cyclic stability was tested by performing 30,000 galvanostatic charge–discharge (GCD) cycles and the electrode exhibited 65% capacitance retention, showing its excellent electrochemical performance and ultra-long cycle life. The excellent electrochemical electrode properties are attributed to the unique processing technique, optimum processing parameters, improved conductivity due to the presence of rGO, and highly porous morphology which offers a high specific surface area. The novel photonic processing we report allows for high-temperature heating of the precursor films achieved via non-radiative recombination of photogenerated electron holes pairs during irradiation. Such extremely quick (ms) heating followed by instantaneous cooling results in the formation of a dense and robust bottom layer of the electrode, resulting in a long cycle life. Full article

The use of indirect electrical techniques is gaining interest for monitoring the corrosion of steel in concrete as they do not require any connection to the rebar. In this paper, we provide insights into the physical aspects of the indirect galvanostatic pulse (GP) method in the Wenner configuration. Considering uniform corrosion, the instantaneous ohmic drop is decreased due to the presence of the rebar, which acts as a short-circuit. However, we observed that this phenomenon is independent of the electrochemical parameters of the Butler–Volmer equation. They are, however, responsible for the nonlinear decrease of the current that polarizes the rebar over time, especially for a passive rebar due to its high polarization resistance. This evolution of the resulting potential difference with time is explained by the increase of the potential difference related to concrete resistance and the global decrease of the potential difference related to the polarization resistance of the rebar. The indirect GP technique is then fundamentally different than the conventional one in three-electrode configuration, as here the steady-state potential is not only representative of polarization resistance but also of concrete resistance. Considering non-uniform corrosion, the presence of a small anodic area disturbs the current distribution in the material. This is essentially due to the different capability of anodic and cathodic areas to consume the impressed current, resulting in slowing down the evolution of the transient potential as compared to uniform corrosion. Hence, highly corroding areas have a greater effect on the transient potential than on the steady-state one. The use of this temporal evolution is thus recommended to qualitatively detect anodic areas. For the estimation of their length and position, which is one of the main current problematic issue when performing any measurement on reinforced concrete (RC) structures with conventional techniques, we suggest adjusting the probe spacing to modulate the sensitivity of the technique. Full article

The electrochemical galvanostatic pulse method (GPM) is used for the evaluation of the degree of corrosion risk of reinforcement in concrete. This non-destructive method enables determining the corrosion promoting conditions through the measurements of reinforcement stationary potential and concrete cover resistivity, and determining the probability of reinforcement corrosion in the tested areas. This method also allows for the estimation of the reinforcement corrosion activity and the prediction of the development of the corrosion process on the basis of corrosion current density measurements. The ambient temperature (and the temperature of the examined element) can significantly affect the values of the measured parameters due to electrochemical character of the processes as well as specific measurement technique. Differences in the obtained results can lead to a wrong interpretation of reinforcement corrosion risk degree in concrete. The article attempts to assess the effect of temperature on the measured parameters while using the galvanostatic pulse method. The GP-5000 GalvaPulse^TM set was used. The results of this study confirmed the impact of temperature changes on the values of three measured parameters (reinforcement stationary potential, concrete cover resistivity, and corrosion current density) and contributed to catching the trend of these changes. Full article