Porosity of materials, understood as an overall averaged parameter or as the pore-size distribution related data is an important quality of numerous functional materials including proton conductive glasses. While most of the existing techniques applied for its assessment cannot be used to monitor the behaviour of ‘live’ systems in operando conditions, it is possible to use Electrochemical Immittance Spectroscopy (EIS) for this purpose. Nevertheless, analysis of these systems still requires an approximation made using transmission lines based models, which can be equated to specific diffusion elements parameters, which can in turn be related to qualities of the porous material investigated. The changes of these parameters can be correlated with various processes– such as dehydration and phase transitions or to the material’s processing history. In this part of the material we present a case study of highly grinded, mechanochemically processed powder-pressed proton conductors: phosphate-silicate glass and two uranyl based compounds– hydroxy phosphate (HUP) and hydroxy arsenate, delivering proof that the dispersive properties of proton transporting materials can be correlated with their dehydration processes, which were followed by means of FT-IR and terahertz time domain spectroscopies.

A number techniques exist to assess the porosity of materials, however a large number of them cannot be used to monitor the behaviour of such in ‘live’ systems. This problem can be overcome by the usage of Electrochemical Impedance Spectroscopy (EIS). However, porous systems and their qualities, can not be easily described using regular equivalent circuit and basic elements. An approximation of such has to be made using transmission lines, which can, in turn, be equated to specific diffusion elements. The parameters of these elements can be related to porous material qualities. And in turn, the changes of these parameters can then be related to various processes—such as ageing or degeneration. In this part of the material a case study was performed on a number of lead-acid systems—a VRLA battery, a maintenance-free one and system consisting of a lead electrode and a platinum mesh counter electrode. This was done in order to test the validity of using the Warburg impedance element in equivalent circuits. During the course of the tests it was found that not only a Gerischer element is a better choice, but the changes in its parameters can be related to different ageing-related processes.

The introduction of the hydrogen economy, despite its obvious technological problems, creates a need for a significant number of niche-focused solutions, such as small-sized (10–100 W) fuel cells able to run on hydrogen of lesser purity than what is considered a standard in the case of PEMFCs. One of the solutions can be derived from the fact that an increase in the operational temperature of a cell significantly decreases its susceptibility to catalyst poisoning. Electrolytes suitable for the so-called medium temperature operational range of 120–400 °C, hence developed, are neither commercialized nor standardized. Among them, phosphate silicate protonically conductive glasses were found not only to reveal interestingly high levels of operational parameters, but also, to exhibit superior chemical and electrochemical stability over their polymeric counterparts. On the other hand, their mechanical properties, including cracking fragility, still need elaboration. Initial studies of the composite phosphate silicate glasses with uranyl-based protonic conductors, presented here, proved their value both in terms of application in fuel cell systems, and in terms of understanding the mechanism governing the charge transport mechanism in these and similar systems. It was found that whereas systems containing 10–20 wt% of the crystalline additive suffer from significant instability, materials containing 45–80 wt% (with an optimum at 60%) should be examined more thoughtfully. Moreover, the uranyl hydrogen phosphate was found to surpass its arsenate counterpart as an interesting self-healing behavior of the phase structure of the derived composite was proved.

Lead–acid batteries remain widely used as backup power sources in distributed industrial infrastructure, where reliable State-of-Health (SoH) assessment is sometimes complicated by poorly documented service histories and uncontrolled environmental exposure. This study examines 12 field-deployed 12 V valve-regulated lead–acid (VRLA) batteries repres1enting six commercial models, withdrawn from medium-voltage grid-management devices after five years of service. Their condition was evaluated using temperature-dependent capacity testing, open-circuit voltage (OCV) measurements, and electrochemical impedance spectroscopy (EIS). The measurements revealed pronounced and highly non-uniform degradation. At −25°C, none of the tested battery types delivered more than 30% of their nominal capacity. More importantly, several batteries exhibiting apparently normal OCV values of 13.2–13.3 V retained only 10–30% of their nominal capacity during discharge, demonstrating that voltage measurements alone may substantially overestimate the availability of backup power. Advanced degradation was also manifested by non-linear discharge profiles and anomalous, physically non-interpretable impedance spectra, providing diagnostic information not evident from OCV measurements. These findings show that OCV-based screening alone is insufficient for reliable SoH assessment of aged VRLA batteries used in emergency power applications. For distributed industrial installations, practical monitoring protocols should therefore combine temperature-aware rapid electrical diagnostics, particularly impedance- or internal resistance-based screening, with periodic reference capacity tests and replacement criteria based on application-specific minimum-capacity requirements.

Premature failure of industrial lead–acid batteries can arise not only from conventional aging but also from atypical environmental exposure that changes the chemistry and morphology of corrosion products. This study presents a focused post mortem investigation of three industrial flooded lead–acid batteries that underwent premature failure shortly after building renovation, despite differing in manufacturer, nominal capacity, operational target, and service time. Corrosion products collected from electrolytes, bridges, and terminals were examined by Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and complementary electrochemical testing of lead-based alloys in sulfuric acid. Raman spectra indicated mixtures of α- and β-PbO₂, PbSO₄, and trace PbS, whereas XRD identified the dominant crystalline phases as PbO₂ polymorphs, PbO, PbSO₄, and Pb₃O₄. The absence of a strong PbS signal in XRD is consistent with its low amount, poor crystallinity, and surface-localized occurrence. SEM images showed loose corrosion products rather than a dense protective layer. The combined evidence indicates an atypical, sulfide-associated corrosion pattern. External H₂S exposure is considered as one possible source of sulfur-containing species; however, no atmospheric H₂S measurements, renovation-material analyses, or controlled exposure tests were performed.