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The performance of Li-O2 batteries is typically evaluated by specific capacity and cyclability in order to facilitate quantitative comparison in literature. The accuracy of such comparison is limited, however, due to the wide range of factors which control the reported specific capacities. These comparisons are not always fair as some factors, which can highly influence the obtained specific capacities, are often neglected. A rigorous and systematic study has been conducted in order to identify the isolated effect of diverse parameters on the performance of these promising batteries. The analysis of cells with different carbon contents reveals that the discharge reactions do not necessarily take place throughout the electrode mass, but instead occur preferentially in closest proximity to the oxygen gas-electrolyte interface. The effective activity of the cathode material is therefore reduced as distance from this interface increases. This work demonstrates that the lack of standardized measurement protocols hinders the rapid development of this technology due to the difficulties inherent in the direct comparison of cells with wide-ranging measurement conditions. In addition, it has been demonstrated that both the employed carbon loading and current rate critically affect cycling lifetime. [ABSTRACT FROM AUTHOR]

The La1- xCa xFe0.8Ni0.2O3- δ (0 ≤ x ≤ 0.9) system is investigated for potential application as a cathode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). A broad range of experimental techniques have been utilized in order to elucidate the characteristics of the entire compositional range. Low A-site Ca content compositions ( x ≤ 0.4) feature a single perovskite solid solution. Compositions with 40% Ca content ( x = 0.4) exhibit the highest electrical and ionic conductivities of these single phase materials (250 and 1.9 × 10−3 S cm−1 at 800 °C, respectively), a level competitive with state-of-the-art (La,Sr)(Fe,Co)O3. Between 40 and 50% Ca content (0.4 > x > 0.5) a solubility limit is reached and a secondary, brownmillerite-type phase appears for all higher Ca content compositions (0.5 ≤ x ≤ 0.9). While typically seen as detrimental to electrochemical performance in cathode materials, this phase brings with it ionic conductivity at operational temperatures. This gives rise to the effective formation of pseudo-composite materials which feature significantly enhanced performance characteristics, while also providing the closest match in thermal expansion behavior to typical electrolyte materials. This all comes with the advantage of being produced through a simple, single-step, low-cost production route without the issues associated with typical composite materials. The highest performing pseudo-composite material ( x = 0.5) exhibits electronic conductivity of 300-350 S cm−1 in the 600-800 °C temperature range while the best polarisation resistance ( Rp) values of approximately 0.2 Ω cm2 are found in the 0.5 ≤ x ≤ 0.7 range. [ABSTRACT FROM AUTHOR]

Abstract: One of the most important challenges for further development of solid oxide fuel cells is to design new electrodes which operate at intermediate temperatures. In this sense, the formation of nanostructures of the Pr0.6Sr0.4Fe0.8Co0.2O3:Ce0.8Sm0.2O2 composite and their characterization have been carried out. These nanostructures have been synthesized using polymeric membranes with 0.1μm pore size as templates. The electronic microscopy has been used in order to confirm the dimensions of the obtained nanotubes with a wall thickness of 20nm. The impedance spectroscopy measurements reveal the good performance of these nanostructured materials and the effect that the nanostructures and the addition of a pure ionic conductor have on the electrochemical performance. The synthesized nanostructured composite exhibits an area specific resistance (ASR) value smaller than that obtained for the sample without the nanostructured morphology together with the addition of the pure ionic conductor. [Copyright &y& Elsevier]

Secondary zinc-air batteries (ZABs) offer a promising alternative for the future of sustainable energy storage. However, the current capability of secondary ZABs is far from satisfactory. The limitations for achieving high reversibility are mainly related to the bifunctional air electrodes as it severely hampers practical applications and commercialization of secondary ZABs. Many efforts have been devoted to the development of efficient and corrosion resistant bifunctional electrocatalysts towards oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In ZABs, carbon is commonly used as conductive additive, however, it has been observed that carbon materials are not resistant to the high positive voltages applied in electrical recharge. In this work, the use of metallic nickel as alternative conductive additive in bifunctional air electrodes is explored and compared with carbon nanotubes (CNT). We demonstrate that the chemical resistance of CNT does not limit the electrode performance; but the density of the additive as well as its interaction with the active material is crucial for achieving long cycle life. The use of Ni as conductive agent in secondary ZABs boosted the cycle life by delivering more than 2,400 cycles, in contrast to the 88 cycles delivered by the analogous carbon-based battery. [ABSTRACT FROM AUTHOR]

Electrically rechargeable zinc-air batteries have gained great attention in recent years due to their capacity to provide high energy density. The electrolyte has played a key role in the advancement of this technology and recently, aqueous chloride-based electrolytes have been demonstrated as a possible alternative to the traditional alkaline system. This study investigates, for the first time, the selection of an optimal bifunctional air electrode (BAE) formulation in two aqueous chloride-based electrolytes (pH4 and pH8) for zinc-air batteries. The effect of different Mn x O y -based catalysts and carbon materials with different electrode formulations are electrochemically analyzed in the two electrolytic systems. The BAE formulation containing 20 wt% γ-MnO 2 , 70 wt% carbon nanotubes (CNT) and 10 wt% PTFE demonstrated the lowest overpotential, among all studied formulations, in both electrolytes. The cycling tests carried out using the selected electrode formulation, at both pH4 and pH8, reveal stable discharge-charge cycling over 400 h with an overpotential lower than 1.1 V. Moreover, the absence of manganese dissolution for the pH8 electrolyte is confirmed by ICP analysis, which overcomes the issue concerning the dissolution of manganese in more acidic media. Contrary to what is stated in conventional alkaline zinc-air batteries, where α-MnO 2 is the most promising catalyst, this study highlights the potential of γ-MnO 2 -based BAEs when using aqueous chloride-based electrolyte. [ABSTRACT FROM AUTHOR]