The Latin Leaflet, Number 29

Polymer electrolytes represent the ultimate in terms of desirable properties of energy storage/conversion devices, as they can offer an all-solid-state construction, a wide variety of shapes and sizes, light-weight, low costs, high energy density and safety. Here we present our recent results concerning a novel strategy for preparing efficient polymer membranes which are successfully demonstrated as suitable electrolytes for several energy conversion and storage devices (i.e., Li- and Na-based batteries and DSSCs). Highly ionic conducting polymer electrolytes containing PEO-based functionalities and different components (e.g., Li/Na salts, RTILs, natural biosourced and cellulosic fillers) are successfully prepared via a rapid process and, directly or subsequently, cross-linked via UV irradiation (patent pending, PCT/IT2014/000008). All the prepared materials are thoroughly characterised in terms of their physical, chemical and morphological properties and tested for their electrochemical performances and durability. The UV-curing process on such materials led to the production of elastic and resistant amorphous macromolecular networks. Noticeably increased ionic conductivities are registered (10-3 S cm-1 at RT), along with very stable interfacial and storage stability and wide electrochemical stability windows. The different lab-scale solid-state devices show remarkable performances even at ambient temperature, at the level of those using liquid electrolytes, respect to which demonstrate much greater durability and safety. The obtained findings demonstrate a new, easy and low cost approach to fabricate and tailor-make polymer electrolytes with highly promising prospects for the next generation of advanced flexible energy production and storage devices

Sustainable electrochemistry - Functional applied materials and techniques for energy devices and sensing (GEI 2018): Foreword

In this Virtual Special Issue of Electrochimica Acta, we gather a selection of scientific research articles corresponding to contributions presented at the Italian Electrochemistry Days (Giornate dell'Elettrochimica Italiana) Edition 2018 – GEI 2018, the yearly event that gathers the national electrochemical community, which was held at the Olympic Village Hotel in Sestriere (Torino), built for the 2006 Winter Games, with panoramic views toward one of the most famous Europe's skiing resorts on the mountains of the north-west side of Italy

Rotational velocities of A-type stars I. Measurement of vsini in the southern hemisphere

Within the scope of a Key Programme determining fundamental parameters of stars observed by HIPPARCOS, spectra of 525 B8 to F2-type stars brighter than V=8 have been collected at ESO. Fourier transforms of several line profiles in the range 4200-4500 A are used to derive vsini from the frequency of the first zero. Statistical analysis of the sample indicates that measurement error is a function of vsini and this relative error of the rotational velocity is found to be about 6% on average. The results obtained are compared with data from the literature. There is a systematic shift from standard values from Slettebak et al. (1975), which are 10 to 12% lower than our findings. Comparisons with other independent vsini values tend to prove that those from Slettebak et al. are underestimated. This effect is attributed to the presence of binaries in the standard sample of Slettebak et al., and to the model atmosphere they used.Comment: 17 pages, includes 18 figures, accepted in A&

Li1.4Al0.4Ge0.4Ti1.4(PO4)3 promising NASICON-structured glass-ceramic electrolyte for all-solid-state Li-based batteries: Unravelling the effect of diboron trioxide

Li-ion batteries (LIBs) are the ubiquitous technology to power portable electronics; however, for the next-generation of high-performing electrochemical energy storage systems for electric vehicles and smart grid facilities, breakthroughs are needed, particularly in the development of solid-state electrolytes, which may allow for enhanced energy density while enabling lithium metal anodes, combined with unrivalled safety and operative reliability. In this respect, here we present the successful synthesis of a glass-ceramic Li1.4Al0.4Ge0.4Ti1.4(PO4)3 NASICON-type solid-state electrolyte (SSE) through a melt-casting technique. Being grain boundaries crucial for the total ionic conductivity of SSEs, the effect of the addition of diboron trioxide (B2O3, 0.05 wt.%) to promote their liquefaction and restructuring is investigated, along with the effects on the resulting microstructures and ionic conductivities. By the thorough combination of structural-morphological and electrochemical techniques, we demonstrate that bulk materials show improved performance compared to their powder sintered counterpart, achieving remarkable ion mobility (> 0.1 mS cm–1 at –10 °C) and anodic oxidation stability (> 4.8 V vs Li+/Li). The addition of B2O3 positively affects the grain cohesion and growth, thus reducing the extension of the grain boundaries (and the related grain/grain interface resistance) and, therefore, increasing the overall ion mobility. In addition, B2O3 is seen to contrast the microcracks formation in the LAGTP system under study which, overall, shows very promising prospects as SSE for the next-generation of high-energy density, safe lithium-based batteries

Melt-casted Li1.5Al0.3Mg0.1Ge1.6(PO4)3 glass ceramic electrolytes: A comparative study on the effect of different oxide doping

The development of Li-ion conducting solid-state electrolytes (SSEs) is crucial to achieve increased energy density, operative reliability, and unprecedented safety to replace the state-of-the-art Li-ion battery (LIB). In this regard, we here present the successful melt-casting synthesis of a MgO-added NASICON-type LAGP glass-ceramic electrolyte with composition Li1.5Al0.3Mg0.1Ge1.6(PO4)3, namely LAMGP. The effects of three different additional oxides are investigated, with the aim to improve grain cohesion and consequently enhance Li-ion conductivity. Specifically, yttrium oxide (Y2O3, 5 mol%), boron oxide (B2O3, 0.7 mol%) and silicon oxide (SiO2, 2.4 %mol) are added, yielding LAMGP-Y, LAMGP-B and LAMGP-Si, respectively. Their effects are exhaustively compared in terms of thermal, crystalline, structural/morphological and ion conducting features. Among the three oxides, B2O3 is able to positively act on grain boundaries without bringing along grains deformation and insulating secondary phases formation, achieving enhanced ionic conductivity of 0.21 mS cm-1 at 20 °C as compared to 0.08 mS cm-1 for a commercial LAGP subjected to the same thermal treatment. A remarkable anodic oxidation stability up to 4.8 V vs Li+/Li is assessed by LAMGP-B system, which accounts for promising prospects for its use in combination with high-energy (high-V) cathodes

A flexible and portable harvesting-storage device by quasi-solid-state supercapacitor and dye-sensitized solar cell integration

In recent years the utilization of power in off grid conditions is dramatically increasing. For this reason research is putting much effort in obtaining improvements in energy storage devices efficiencies and in discovering alternatives concerning easiness of fabrication that can be industrially implemented. In this framework, integration of energy storage devices with energy harvesting systems is obtaining more and more significance since the amount of energy that can be stored especially in Electrochemical Double Layer Capacitors (EDLCs) is limited. To this purpose, herein we present an innovative flexible integrated device composed by a symmetrical aqueous EDLC and a TiO2 nanotubes-based Dye Sensitized Solar cell (DSSC). A UV photo-polymerized quasi-solid electrolyte was used in both sections. At first a self-standing flexible polymer matrix was fabricated starting from Bisphenol A ethoxylate dimethacrylate (BEMA) and poly (ethylene glycol) methyl ether methacrylate (PEGMA), adding a 3% by weight of 2hydroxy-2-methyl-1-phenyl-1-propanone (Darocur 1173) as photoinitiator. Then, the matrix was soaked in two different liquid electrolytes, a 2 M NaCl aqueous solution for the energy storage section and an Iodine-based liquid electrolyte for the DSSC unit. This is the first work in which this type of polymer electrolyte membrane is used for an EDLC. The electrodes were fabricated onto Stainless-steel and Titanium grids, for EDLC and DSSC respectively. TiO2 nanotubes were grown by means of anodic oxidation as photoanode semiconductor material, while EDLC active material was composed by 85% of graphene nanoplatelets and 15% of Acetylene Black. The harvesting-storage device (HSD) was sealed by a light-cured photo-polymerization method. The measured overall photon-to-electrical conversion and storage efficiency for the HSD was 1.02% under standard test conditions. This value increases for lower illumination conditions reaching 1.46% at 0.3 Sun

Photoanodes for Aqueous Solar Cells: Exploring Additives and Formulations Starting from a Commercial TiO2 Paste

Whereas the commercialization of dye‐sensitized solar cells (DSSCs) is finally proceeding taking advantage of their low cost and tunable optical features, such as colour and transparency for both indoor and building‐integrated applications, the corresponding aqueous counterpart is still at its infancy. As the TiO2 electrode is a fundamental component for hybrid solar cells, this work investigates the effect of different molecular (α‐terpineol, propylene carbonate) and polymeric (polyethylene oxide, polyethylene glycol, carboxymethyl cellulose and xanthan gum) additives that can be introduced into a commercial TiO2 paste for for screen‐printing (or doctor blade). Among all, the addition of polyethylene glycol leads to the best cell performances, with markedly increased short‐circuit current density (+18 %) and power conversion efficiency (+48 %) with respect to the pristine (commercial) counterpart. When further explored at different concentration levels, electrodes fabricated from polyethylene glycol‐based pastes show different morphologies, thicknesses and performances, which are investigated through (photo)electrochemical, structural, physical‐chemical and microscopic techniques

Photoanodes for Aqueous Solar Cells: Exploring Additives and Formulations Starting from a Commercial TiO2 Paste

Whereas the commercialization of dye‐sensitized solar cells (DSSCs) is finally proceeding taking advantage of their low cost and tunable optical features, such as colour and transparency for both indoor and building‐integrated applications, the corresponding aqueous counterpart is still at its infancy. As the TiO2 electrode is a fundamental component for hybrid solar cells, this work investigates the effect of different molecular (α‐terpineol, propylene carbonate) and polymeric (polyethylene oxide, polyethylene glycol, carboxymethyl cellulose and xanthan gum) additives that can be introduced into a commercial TiO2 paste for for screen‐printing (or doctor blade). Among all, the addition of polyethylene glycol leads to the best cell performances, with markedly increased short‐circuit current density (+18 %) and power conversion efficiency (+48 %) with respect to the pristine (commercial) counterpart. When further explored at different concentration levels, electrodes fabricated from polyethylene glycol‐based pastes show different morphologies, thicknesses and performances, which are investigated through (photo)electrochemical, structural, physical‐chemical and microscopic techniques

Recent advances in eco-friendly and cost-effective materials towards sustainable dye-sensitized solar cells

Dye-sensitized solar cells (DSSCs), as emerging photovoltaic technology, have been thoroughly and extensively investigated in the last three decades. Since their first appearance in 1991, DSSCs have gained increasing attention and have been classified as feasible alternatives to conventional photovoltaic devices due to their numerous advantages, such as cheap and simple preparation methods, the possibility of being integrated in buildings and astonishing performances under indoor and diffuse illumination conditions. Photoconversion efficiencies of up to 14% and 8% have been obtained for lab-scale devices and modules, respectively. Albeit the efforts made, these values seem arduous to be outdone, at least under simulated solar radiation. Nevertheless, recent lab-scale systems have demonstrated photoconversion efficiencies of up to 33% under indoor illumination (i.e. 1000 lux) leading to an actual Renaissance (or Revival) of these devices. It is worth mentioning that scientists in this field are developing innovative materials aiming at long-term and efficient devices, being the concept of sustainability often set apart. However, in light of effective commercialization of this technology, stability, efficiency and sustainability should be considered as the essential keywords. Nowadays, DSSCs are finding a “new way back” towards sustainability and rather a huge number of reports have focused on the preparation of green and cost-effective materials to replace the standard ones. In this scenario, the present review aims to give an overview of the most adopted strategies to enhance the sustainability of materials in classical DSSC components (e.g. sensitizer, redox couple, electrolyte and counter-electrode), including smart synthesis and deposition procedures, which currently represent utmost important topics in the scientific community