Unraveling the Effect of Singlet Oxygen on Metal-O2 Batteries: Strategies Toward Deactivation

Aprotic metal-O(2)batteries have attracted the interest of the research community due to their high theoretical energy density that target them as potential energy storage systems for automotive applications. At present, these devices show various practical problems, which hinder the attainment of the high theoretical energy densities. Among the main limitations, we can highlight the irreversible parasitic reactions that lead to premature death of the battery. The degradation processes, mainly related to the electrolyte, lead to the formation of secondary products that accumulate throughout the cycling in the air electrode. This accumulation of predominantly insulating products results in the blocking of active sites, promoting less efficiency in system performance. Recently, it has been discovered that the superoxide intermediate radical anion is involved in the generation of the reactive oxygen singlet species (O-1(2)) in metal-O(2)batteries. The presence of singlet oxygen is intimately linked with electrolyte degradation processes and with carbon-electrode corrosion reactions. This review analyzes the nature of singlet oxygen, while clarifying its toxic role in metal-O(2)batteries. Besides, the main mechanisms of deactivation of singlet oxygen are presented, trying to inspire the research community in the development of new molecules capable of mitigating the harmful effects related to this highly reactive species.This work was supported by the Ministerio de Economia y Competitividad of Spain (under projects MAT2016-78266-P and PID2019-107468RB-C21), the Fondo Europeo de Desarrollo Regional (FEDER), and the Eusko Jaurlaritza/Gobierno Vasco (under project IT1226-19). NO-V also acknowledges the Basque Government (Elkartek CICe2020, KK-2020/00078) for the financial support of this work

Designing Perovskite Oxides for Solid Oxide Fuel Cells

Perovskite-type oxides with the general formula ABO3 have been widely studied and are utilized in a large range of applications due to their tremendous versatility. In particular, the high stability of the perovskite structure compared to other crystal arrangements and its ability, given the correct selection of A and B cations, to maintain a large oxygen vacancy concentration makes it a good candidate as electrode in solid oxide fuel cell (SOFC) applications. Utilizing this novel structure allows the engineering of advanced, effective electrolytes for such devices. This review details the development of current state-of-the-art perovskite-type oxides for solid oxide fuel cell (SOFC) applications

Controlling the triple phase boundary on Na-O-2 battery cathodes with perfluorinated polymers

Sodium-oxygen batteries hold great promise for the transition to a non-fossil fuel economy due to their high theoretical energy density. One of the most important components of these devices is the air-cathode, where the electrons available at the solid electrode, the Na+ ions present in the liquid electrolyte and oxygen gas react to form sodium oxides as discharge products. The kinetics of the discharge/charge reactions depend significantly on the boundary points between the solid-liquid-gas reaction phases, known as triple phase boundary (TPB). The density of TPB points (and therefore the battery efficiency) can be maximized by incorporating perfluorinated polymers on the cathode formulation. Thus, this type of polymers enhance oxygen transport properties which favour the diffusion of gaseous components in detriment to liquid electrolytes on solid electrodes. In this work, polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene (FEP) polymers were added in different weight ratio to commercial graphene nanoplatelets (GNPs) cathodes. The critical physical properties affecting the formation of the TPB have been identified and correlated to sodium-oxygen battery performance. These key properties, which are crucial to modulate the oxygen diffusion within the cathode structure, have been identified for the first time in this work for aprotic metal air devices. This approach is of outmost importance for the development or efficient electrochemical storage devices where oxygen gas is involved.This work was funded by the European Union (Graphene Flagship-Core 3, Grant No. 881603) and the R&D&I project PID2020–117626RA-I00, funded by MCIN/AEI/10.13039/501100011033. N. Ortiz-Vitoriano thanks Ramon y Cajal grant (RYC-2020-030104-I) funded by MCIN/AEI/10.13039/501100011033 and by FSE invest in your future

Nanostructured Gd0.8Sr0.2Fe0.8M0.2O3 (M=Cr, Ga) materials for solid oxide fuel cell cathodes

AbstractPolycrystalline samples of Gd0.8Sr0.2Fe0.8M0.2O3 (M=Cr, Ga) are prepared by combustion route and pore wetting technique in order to compare the influence of the morphology in the performance of two cathodes for Solid Oxide Fuel Cells. When polycarbonate membranes are used as templates nanowire arrays with a diameter of 50–70 nm are obtained. Comparing the results obtained by Electrochemical Impedance Spectroscopy (EIS) measurements, it is clearly observed that the cathodic resistance considerably decreases when optimized synthesis parameters are used, obtaining a better performance for the Gd0.8Sr0.2Fe0.8Ga0.2O3 nanowires with an area specific resistance (ASR) value at 850∘C of 0.195 Ω cm2

High performance carbon free bifunctional air electrode for advanced zinc-air batteries

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.This work was supported by CDTI (ALMAGRID of the “CERVERA Centros Tecnológicos” program, CER-20191006), the Basque Country Government (CIC energiGUNE’20 of the ELKARTEK program, N° Exp. KK-2020/0078), the European Commission through the project ZABCAT “A New Zn-Air Battery Prototype to Overcome Cathode Degradation Through Catalyst Confinement” (grant agreement 966743) and the Ministerio de Ciencia e Innovación through the project AVANZA “Advanced Zn-Air Battery Prototype for the Energy Transition Horizon” (TED2021-131451B-C22). N. Ortiz-Vitoriano thanks Ramon y Cajal grant (RYC-2020-030104-I) funded by MCIN/AEI/10.13039/501100011033 and by FSE invest in your future

High Performance Na-O2 Batteries and Printed Microsupercapacitors Based on Water-Processable, Biomolecule-Assisted Anodic Graphene

Integrated approaches that expedite the production and processing of graphene into useful structures and devices, particularly through simple and environmentally friendly strategies, are highly desirable in the efforts to implement this two-dimensional material in state-of-the-art electrochemical energy storage technologies. Here, we introduce natural nucleotides (e.g., adenosine monophosphate) as bifunctional agents for the electrochemical exfoliation and dispersion of graphene nanosheets in water. Acting both as exfoliating electrolytes and colloidal stabilizers, these biomolecules facilitated access to aqueous graphene bio-inks that could be readily processed into aerogels and inkjet-printed interdigitated patterns. Na-O2 batteries assembled with the graphene-derived aerogels as the cathode and a glyme-based electrolyte exhibited a full discharge capacity of ∼3.8 mAh cm–2 at a current density of 0.2 mA cm–2. Moreover, shallow cycling experiments (0.5 mAh cm–2) boasted a capacity retention of 94% after 50 cycles, which outperformed the cycle life of prior graphene-based cathodes for this type of battery. The positive effect of the nucleotide-adsorbed nanosheets on the battery performance is discussed and related to the presence of the phosphate group in these biomolecules. Microsupercapacitors made from the interdigitated graphene patterns as the electrodes also displayed a competitive performance, affording areal and volumetric energy densities of 0.03 μWh cm–2 and 1.2 mWh cm–3 at power densities of 0.003 mW cm–2 and 0.1 W cm–3, respectively. Taken together, by offering a green and straightforward route to different types of functional graphene-based materials, the present results are expected to ease the development of novel energy storage technologies that exploit the attractions of graphene.Funding by the Spanish Ministerio de Economía y Competitividad (MINECO) and the European Regional Development Fund (ERDF) through project MAT2015-69844-R and by the Spanish Ministerio de Ciencia, Innovación y Universidades and ERDF through project RTI2018-100832-B-I00 is gratefully acknowledged. Partial funding by Plan de Ciencia, Tecnología e Innovación (PCTI) 2013-2017 del Principado de Asturias and the ERDF through project IDI/2018/000233 is also acknowledged. J.M.M. is grateful to the Spanish Ministerio de Educación, Cultura y Deporte (MECD) for his pre-doctoral contract (FPU14/00792). J.N.C. acknowledges the ERC Adv. Gr. FUTUREPRINT. This work was also financially supported by the European Union (Graphene Flagship, Core 2, Grant number 785219).Peer reviewe

Manganese hexacyanoferrate reinforced by PEDOT coating towards high-rate and long-life sodium-ion battery cathode

Prussian blue analogues hold great promise as cathodes in sodium ion batteries. Among Prussian blue analogues, manganese hexacyanoferrate is desirable because of its high working voltage, as well as its high specific capacity and low cost. However, poor cycling stability and unsatisfactory rate capability of manganese hexacyanoferrate, which are mainly caused by poor intrinsic conductivity, phase transition, side reactions, and transition metal dissolution, extremely limit its practical application. In this work, we demonstrate a high-rate and long-life MnHCF@PEDOT sodium ion battery cathode through a facile in situ polymerization method. Benefitting from the synergistic effect of the inhibited Mn/Fe dissolution, suppressed phase transition, and improved capacitive storage, the composite electrode exhibits a high capacity of 147.9 mA h g−1 at 0.1C, 95.2 mA h g−1 at a high rate of 10C, and 78.2% capacity retention after 1000 cycles. Furthermore, even at a low temperature of −10 °C, MnHCF@PEDOT still delivers a high capacity of 87.0 mA h g−1 and maintains 71.5 mA h g−1 (82.2%) after 500 cycles

Oxygen reactions on Pt{hkl} in a non-aqueous Na+ electrolyte: site selective stabilisation of a sodium peroxy species

Sodium–oxygen battery cathodes utilise the reversible redox species of oxygen in the presence of sodium ions. However, the oxygen reduction and evolution reaction mechanism is yet to be conclusively determined. In order to examine the part played by surface structure in sodium–oxygen electrochemistry for the development of catalytic materials and structures, a method of preparing clean, well-defined Pt electrode surfaces for adsorption studies in aprotic solvents is described. Using cyclic voltammetry (CV) and in situ electrochemical shell-isolated nanoparticle enhanced Raman spectroscopy (SHINERS), the various stages of oxygen reduction as a function of potential have been determined. It is found that on Pt{111} and Pt{110}-(1 × 1) terraces, a long lived surface sodium peroxide species is formed reversibly, whereas on Pt{100} and polycrystalline electrodes, this species is not detected

Rate-Dependent Nucleation and Growth of NaO2 in Na-O2 Batteries

Understanding the oxygen reduction reaction kinetics in the presence of Na ions and the formation mechanism of discharge product(s) is key to enhancing Na–O2 battery performance. Here we show NaO2 as the only discharge product from Na–O2 cells with carbon nanotubes in 1,2-dimethoxyethane from X-ray diffraction and Raman spectroscopy. Sodium peroxide dihydrate was not detected in the discharged electrode with up to 6000 ppm of H2O added to the electrolyte, but it was detected with ambient air exposure. In addition, we show that the sizes and distributions of NaO2 can be highly dependent on the discharge rate, and we discuss the formation mechanisms responsible for this rate dependence. Micron-sized (∼500 nm) and nanometer-scale (∼50 nm) cubes were found on the top and bottom of a carbon nanotube (CNT) carpet electrode and along CNT sidewalls at 10 mA/g, while only micron-scale cubes (∼2 μm) were found on the top and bottom of the CNT carpet at 1000 mA/g, respectively.Seventh Framework Programme (European Commission) (Marie Curie International Outgoing Fellowship, 2007-2013))National Science Foundation (U.S.) (MRSEC Program, award number DMR-0819762)Robert Bosch GmbH (Bosch Energy Research Network (BERN) Grant)China Clean Energy Research Center-Clean Vehicles Consortium (CERC-CVC) (award number DE-PI0000012)Skolkovo Institute of Science and Technology (Skoltech-MIT Center for Electochemical Energy Storage