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There is a critical need for higher performing proton exchange membranes for electrochemical energy conversion devices that would enable higher temperature and drier operating conditions to be util...

The electrical relaxation and polarization phenomena of electrospun PVDF (P)/Nafion (N) blended fiber mats ([P/N0.9]M and β–[P]M) and membranes ([P/N0.9]MM) are compared with those of the solvent-c...

The electrical response of zirconia composite polybenzimidazole membranes [PBI4N(ZrO2)x](H3PO4)y is studied by Broadband Electrical Spectroscopy (BES), and correlated with our previous Dynamic Mechanical Analysis (DMA) and Modulated Differential Scanning Calorimetry (MDSC) measurements. The presence of nanofiller in the PBI4N polymer matrix is shown to plasticize the membrane, with a maximum effect observed at a nanofiller loading level of x ≈ 0.13. The disrupting effect of the nanofiller on the interchain dipole interactions modulates the overall electrical response of the materials. Following acid doping, a marked increase in conductivity is observed as new chemistry is installed at the interfaces between polymer and nanofiller that facilitates dipolar fluctuations and segmental motions of the polymer chains. In these composite membranes, two mechanisms of conductivity are postulated based on BES analysis; i) proton hopping between binding sites, and ii) proton hopping at the interfaces between HnPBI4Nn+/HnPBI4Nn+ and HnPBI4Nn+/HmZrO2m+. The results here presented demonstrate the effect of zirconia nanofiller and subsequent acid doping on the conductivity properties of composite PBI4N membranes. Of note, at 100 °C for [PBI4N(ZrO2)0.132](H3PO4)11, conductivity as high as 0.035 S/cm is achieved.

A new family of ionic liquid based electrolytes ([EMImCl/(TiCl 4 ) 1.4 ]/(δ-MgCl 2 ) x ) for electrochemical applications is proposed. These materials are obtained by direct reaction of 1-ethyl-3-methylimidazolium chloride (EMImCl) with titanium(IV) chloride (TiCl 4 ), and doped with increasing amounts of δ-MgCl 2 . Modulated differential scanning calorimetry (MDSC) measurements show that in these electrolytes the glass transition temperature, T g , occurs at −36 °C, and that the crystallization and melting transitions are inhibited by the presence of large and highly amorphous charge delocalized anionic domains. Vibrational studies indicate that in the electrolyte the anionic domains consist of large monomeric and dimeric 3D-catenated halotitanate clusters, in which magnesium chloride units are coordinated to Ti species, and whose equilibrium concentration is modulated by the concentration of δ-MgCl 2 . Density functional theory (DFT) based electronic structure calculations were undertaken to understand the structural features of these materials and to confirm the vibrational frequency assignments. Broadband electrical spectroscopy (BES) studies reveal that the electric response of these materials is modulated by polarization and dielectric relaxation events. These measurements revealed the correlations existent between conductivity mechanisms and the dielectric relaxations of the host matrix of the electrolytes. At 40 °C, the conductivity is found to depend on the δ-MgCl 2 concentration and approximately on the order of 10 −4 S cm −1 . Preliminary electrochemical measurements reveal a reversible deposition and stripping process of a Mg-Ti alloy, with an average columbic efficiency of 99.3% and a deposition overvoltage of only 10 mV.

A new type of polymer blend, prepared by electrospinning nanofibers containing the immiscible polymers polyvinylidene fluoride (PVDF, 10 wt%) and Nafion® perfluorosulfonic acid (90 wt%), has been characterized experimentally. The internal nanofiber morphology is unique and unlike a normal blend, with individual phase-separated and randomly distributed fibrils of Nafion and PVDF (∼2-7 nm in diameter) that are bundled together and aligned in the fiber axis direction (where the fiber diameter is ∼500 nm). This morphology is retained when fiber mats are hot-pressed into dense films. The physicochemical properties of the electrospun blended fibers are also highly unusual and unanticipated. As shown in this study, each polymer component influences the thermal and structural behavior of the other, especially in the dry state. Thus, dry composite polymer mats and membranes exhibit properties and attributes that are not observed for either pure PVDF or pure Nafion. Experimental results indicate that: (i) PVDF imparts conformational constraints on the polytetrafluoroethylene (PTFE) backbone chains of Nafion, resulting in an increased 21 helical conformation that effects Nafion's water uptake and thermal properties; and (ii) dipole-dipole interactions between PVDF polymer chains and Nafion make the β-phase polymorph of PVDF much more stable at elevated temperatures. Such "reciprocal templating" in electrospun fibers may not be unique to Nafion and PVDF, thus the procedure represents a new method of creating nanostructured multi-component polymer materials with innovative features.

A polyketone-b-poly[N-(4 methyl-methylpyridium)-ethylenepyrrole+][X−], with X− = I− or OH−, is investigated as an example of anion-exchange membrane with potential applications in fuel cells. The polyketone starting material PK and the functionalized polyketones Pyr-FPKmI and Pyr-FPKmOH are investigated via Broadband Electrical Spectroscopy (BES) to understand the conductivity mechanism. BES signals are collected in the frequency range of 10−2 – 107 Hz and from −100° to 120 °C. BES measurements reveal the presence of up to three interdomain polarizations phenomena, one electrode polarization event and two β dielectric relaxation modes for both wet Pyr-FPKmI and Pyr-FPKmOH. Ion conductivity for Pyr-FPKmI and Pyr-FPKmOH is found to be 0.0086 and 0.0105 S cm−1 at 80 °C, respectively. The overall conductivity mechanism is attributed to the superposition of two conduction pathways, via delocalization bodies and via interdomain percolation pathways, which are associated with two different physical phenomena.

We report on the development of two new Pt-free electrocatalysts (ECs) for the oxygen reduction reaction (ORR) process based on graphene nanoplatelets (GNPs). We designed the ECs with a core-shell morphology, where a GNP core support is covered by a carbon nitride (CN) shell. The proposed ECs present ORR active sites that are not associated with nanoparticles of metal/alloy/oxide but are instead based on Fe and Sn subnanometric clusters bound in coordination nests formed by carbon and nitrogen ligands of the CN shell. The performance and reaction mechanism of the ECs in the ORR are evaluated in an alkaline medium by cyclic voltammetry with the thin-film rotating ring-disk approach and confirmed by measurements on gas-diffusion electrodes. The proposed GNP-supported ECs present an ORR overpotential of only ca. 70 mV higher with respect to a conventional Pt/C reference EC including a XC-72R carbon black support. These results make the reported ECs very promising for application in anion-exchange membrane fuel cells. Moreover, our methodology provides an example of a general synthesis protocol for the development of new Pt-free ECs for the ORR having ample room for further performance improvement beyond the state of the art.

This study reports the preparation and characterization of a new family of electrocatalysts (ECs) for the oxygen reduction reaction (ORR) exhibiting a “core-shell” morphology. The “core” consists of graphene sheets, which are covered by a carbon nitride (CN) “shell” embedding Au and Ni active sites. The investigated ECs are labeled AuNi10-CNl 600/Gr and AuNi10-CNl 900/Gr. The chemical composition and thermal stability are studied by inductively-coupled plasma atomic emission spectroscopy (ICP-AES), elemental analysis and by high-resolution thermogravimetric analysis (HR-TGA). The morphology of the ECs is probed by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and powder X-ray diffraction (XRD). The ORR performance of the ECs is studied both in acid (0.1 M HClO4) and in alkaline medium (0.1 M KOH) by Cyclic Voltammetry with the Thin-Film Rotating Ring-Disk Electrode (CV-TF-RRDE) method. Both ECs exhibit a promising performance in the ORR in the alkaline medium.

The centre piece at the heart of numerous energy storage and conversion devices, such as fuel cells and redox flow batteries, is the ion-exchange membrane (IEM). This typically polymeric material is responsible for the migration of ionic species, separation of fuel stocks and for providing additional support to the electrode assemblies. As a result, IEMs are required to possess excellent stability (both thermal and chemical), long lifetimes, electrical insulation, and high ionic conductivity and specificity. Current state-of-the-art polymer electrolytes possessing the more desirable properties tend to come with a price tag that can render their use in energy storage/conversion technologies somewhat cost prohibitive [1]. This has created a strong driving force aimed towards new, cheaper but still high performing materials, for use in energy storage/exchange systems. The copolymerization of carbon monoxide and ethylene (two readily available and cheap feedstocks) leads to the formation of polyketone, a high performance thermoplastic that has found many applications resulting in its global production of thousands of tonnes per annum. The alternating 1,4-dicarbonyl functionality of aliphatic polyketone enables access, via classic Paal-Knorr chemistry, to a variety of new functionalized polymers [2]. Here we present a new ion conducting polymeric material derived from polyketone, that possess N-functionalized pyrrole units in the backbone (FPK) [3]. Ion-conductivities on the order of 10.6 and 8.6 mScm-1 for the hydroxide and iodide forms of methylated FPKs have been achieved at 80 oC, with the hydroxide FPK demonstrating high resistance towards alkaline conditions for over 20 hours at 80 oC. The flexibility in the choice of the N-substituent renders these new materials higher tailorable and potentially useful in a range of energy storage/conversion technologies as either proton or anion exchange membranes. Acknowledgements The authors wish to thank the Strategic Project of the University of Padova “Materials for Membrane-Electrode Assemblies to Electric Energy Conversion and Storage Devices (MAESTRA)” for funding. V.D.N. thanks the University Carlo III of Madrid for granting him the “Catedra de Excelentia” (Chair of Excellence). References [1] S. Eckroad in Handbook of Energy Storage for Transmission or Distribution Applictions, Electric Power Research Institute Report 1007189, California, USA (2002) [2] A. Sen et al., Macromolecules, 22, (1989), 2012, A.A. Broekhuis et al., J. Apply. Polm. Sci., (2016), 42924, A.A. Broekhuis et al., J. Appl. Polym. Sci., 107, (2008), 107, 262, A.A. Broekhuis, Dyes and Pigments, 98, (2013), 51 [3] N. Ataollahi, K. Vezzù, G. Nawn, G. Pace, G. Cavinato, F. Girardi, P. Scardi, V. Di Noto, R. Di Maggio, Electrochimica Acta., 226 (2017) 148-157.

In this study, a new family of poly(vinyl alcohol)-based solid membrane electrolytes is proposed. The single ion conducting polyelectrolytes are obtained by direct lithiation of partially hydrolyzed poly(vinyl alcohol), forming a lithium-poly(vinyl alkoxide) macromolecular salt. Furthermore, in order to improve the ionic conductivity, the obtained polymer is plasticized with 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMImTFSI) ionic liquid. Thermogravimetric analysis demonstrates a thermal stability higher than 215 °C. Differential Scanning Calorimetry studies show a polymer associated glass transition event and a melting transition related to the ionic liquid domains at ca. +80 and −40 °C respectively. Fourier-transform infrared spectroscopy proves that: a) lithiation of the membrane results in an increase to the amorphic character of the polymer backbone; and b) after ionic liquid addition to the lithiated membrane, the effective coordination of lithium cations by the TFSI-anions of the ionic liquid augments the ionic conductivity of the proposed materials. Broadband electrical spectroscopy (BES) investigations reveal that this system is characterized by several polarization phenomena and dielectric relaxation events. Analysis of the BES results, using suitable models, allows for the conductivity mechanism in the proposed polymer electrolytes to be hypothesized. Finally, the ionic conductivity values of 1.29 · 10−5 S cm−1 and 1.92 · 10−3 S cm−1 at 30 and 80 °C render these materials very promising for application in electrochemical devices.

Nafion‑tungsten oxide hybrid membranes, [Nafion/(WO3)x], with varying loading levels of WO3 nanofiller (x = 0, 0.024, 0.329) are prepared and investigated as candidates for application as solid electrolytes in vanadium redox flow batteries (VRFBs). The thermal properties of [Nafion/(WO3)x] hybrid membranes are probed both by high-resolution thermogravimetric analysis (HR-TGA) and by modulated differential scanning calorimetry (MDSC). Vibrational spectroscopy studies are carried out by: (i) Attenuated Total Reflectance - Fourier Transform Infrared spectroscopy (ATR-FTIR); and (ii) Raman spectroscopy, to elucidate the secondary structure of [Nafion/(WO3)x] and study the interactions taking place between the nanofiller and the Nafion matrix. The electrical response of [Nafion/(WO3)x] is determined by Broadband Electrical Spectroscopy (BES) and the permeability towards VO2+ is measured by UV-VIS spectrometry. It is demonstrated that the [Nafion/(WO3)x] hybrid membranes exhibit a high ion selectivity (up to 10.6∙103 S∙min∙cm−3 for [Nafion/(WO3)0.329]) that is much improved in comparison with that characterizing recast Nafion (6.5∙103 S∙min∙cm−3). A structural model and a conductivity mechanism for the [Nafion/(WO3)x] hybrid membranes are proposed, in order to rationalize the experimental results and correlate the electrical response with the transport properties.

New high voltage and high capacity storage systems are needed to sustain the increasing energy demand set by the portable electronics and auto motive fields. Due to their good electrochemical performance, lithium-transition metal-phosphates (LiMPO 4 ) seem to be very attractive as cathode materials for lithium secondary batteries. Here the synthesis and the characterization of fi ve high voltage cathodes for lithium batteries, based on lithium-iron, lithium-nickel, lithium-cobalt phosphates are described. The effect of differing degrees of cobalt and nickel doping on structure, morphology, and the electrochemical properties of the different materials is thoroughly studied. Transition metal atoms in these materials are found to be vicariant within the olivine crystal structure; however, the lattice parameters and cell volume can be modulated by varying the nickel/cobalt ratio during the synthesis. High performance battery prototypes in terms of voltage (>4.0 V), specific capacity (125 mAh g -1 ), specifi c energy (560 mWh g -1 ), and cyclic life (>150 cycles) are also demonstrated.

Relaxation and polarization phenomena of phosphoric acid-doped [PBI4N(HfO 2 ) x ](H 3 PO 4 ) y nanocomposite membranes for high-temperature proton-exchange membrane fuel cells are studied using Dynamic Mechanical Analysis (DMA) and Broadband Electrical Spectroscopy (BES). The membranes are obtained by casting combinations of a polybenzimidazole polymer (PBI4N) with increasing amounts of hafnium oxide nanofiller, resulting in [PBI4N(HfO 2 ) x ] hybrid systems with 0 ≤ x ≤ 0.32. Phosphoric acid at varying content levels (0 ÷ 18 wt%) is used as a doping agent, giving rise to [PBI4N(HfO 2 ) x ](H 3 PO 4 ) y membranes. DMA and BES studies lead us to determine that the electric response of the membranes is modulated by polarization phenomena and by α and β dielectric relaxation events of the polymer matrix. Additionally, the experimental results suggest that in [PBI4N(HfO 2 ) x ](H 3 PO 4 ) y membranes the conductivity occurs owing to three conductivity pathways: two mechanisms involving inter-domain proton migration phenomena by “hopping” events; and one mechanism in which proton exchange occurs between delocalization bodies. These results highlight the significant effect of the hafnium oxide nanofiller content on the conductivity of [PBI4N(HfO 2 ) x ](H 3 PO 4 ) y where, at x ≥ 0.04, demonstrates conductivity higher (9.0 × 10 −2 S/cm) than that of pristine H 3 PO 4 -doped PBI4N (4.8 × 10 −2 S/cm) at T ≥ 155 °C.

An anion exchange membrane (AEM) was made with a modified polyketone (PK). AEMs of polyamines were prepared in a three-step procedure: (I) PK synthesis using ethylene and carbon monoxide, supported by a Pd catalyst, followed by the introduction of 1,2-diaminopropane to yield the polymeric amines; (II) solvent casting of the modified PK with a low degree of amination; (III) iodomethylation to form the AEM (PK-PDAPm(I)), followed by ion exchange with KOH (PK-PDAPm(OH)). The structure of the modified polyketone was characterized using FT-IR, and UV–vis spectroscopy, demonstrating the successful introduction of amine in the PK. The conductivity of the AEM was studied using broadband electric spectroscopy (BES) in the temperature range from −100 to 120 °C: the highest value of 9 × 10 −4 S·cm −1 was reached at 120 °C for the ionic conductivity of PK-PDAPm(I), followed by PK-PDAPm(OH) with values of the same order of magnitude (10 −4 S·cm −1 ). Thermogravimetry showed that the material is thermally stable up to 200 °C.

This report describes the preparation, characterization, and coin cell prototype testing of new Li[Fe 1/3 Ni 1/3 Co 1/3 ]PO 4 high voltage olivine cathodes for lithium secondary batteries (LFNCPs) obtained by treating the precursors with Cu and Cu+C sources. The morphology, structure, interactions, and electrochemical properties of the obtained materials are extensively studied in order to elucidate the interplay in LFNCPs between graphite (C) and copper(II) carbonate (Cu) addition to the precursors and structural flexibility, relaxations, and electrochemical performance of obtained materials. In particular, the investigated LFNCPs cathodes are obtained by treating the reaction precursors with graphite nanoparticles and/or copper(II) carbonate. It is found that copper does not behave like a vicariant metal ion within the olivine structure of the cathodes, instead it forms segregated CuO nanoparticles which improve the charge-transfer kinetics during the charge/discharge processes of the cathode material. The graphite additive in precursors is found to decompose during the synthesis, resulting in an improved elasticity of the 3D structure of the olivine backbone. This increased structural flexibility facilitates the percolation of lithium ions along the 1D channels of the materials during the charge/discharge processes. Coin cell prototypes assembled with the proposed cathode materials show good specific capacities (>100 mAh g −1 ), good specific energies (455 mWh g −1 ), and a high working potential (>4.0 V).

Reactions of Nindigo-BF2 complexes with Pd(hfac)2 produced mixed complexes with Nindigo binding to both a BF2 and a Pd(hfac) unit. These complexes are the first in which the Nindigo ligand binds two different substrates, and provide a conceptual link between previously reported bis(BF2) and bis(Pd(hfac)) complexes. The new Pd/B complexes have intense near IR absorption near 820 nm, and they undergo multiple reversible oxidations and reductions as probed by cyclic voltammetry experiments. The spectral, redox, and structural properties of these complexes are compared against those of the corresponding B2 and Pd2 complexes with the aid of time-dependent density functional calculations. In all cases the low-energy electronic transitions are ligand-centered π-π* transitions, but the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies--and hence the absorption wavelength as well as the oxidation and reduction potentials--are significantly modulated by the moieties bound to the Nindigo ligand.

Reactions of indigo-N,N′-diarylimine (‘Nindigo’) derivatives with BF3·Et2O give mono- or bis-BF2 chelate complexes 2 or 3 respectively. The product distribution between 2 and 3 is sensitive to the auxiliary base and solvent. Although the bis-BF2 complexes 3 are isolable, they gradually decompose in solution to the corresponding mono-BF2 species 2; this process is accelerated by water. The instability of 3 is believed to be due to ring stain effects based on structural analyses of 2. Electrochemical studies of 2 reveal one quasi-reversible oxidation process and two irreversible reductions, whereas derivatives of 3 possess a reversible oxidation and two sequential reversible reductions. The electronic spectra of 2 and 3 contain intense (e ∼ 3 × 104 M−1 cm−1) long-wavelength absorptions near 650 nm and 750 nm respectively. Both series of compounds are weakly emissive in the near-infrared. Time-dependent DFT calculations reveal the electronic transitions to be π–π* in nature.

In this report, the preparation of Fe-carbon nitride (CN)-based electrocatalysts (ECs) with a “core-shell” morphology for the oxygen reduction reaction (ORR) is described. The ECs consist of spherical XC-72R carbon nanoparticles, the “cores”, that are covered by a CN matrix, the “shell”, that embeds Fe species in “coordination nests”. The latter consist of hollow cavities in the CN matrix, whose internal surface is covered by N- and C-ligands able to stabilize alloy nanoparticles or active sites. Two families of CN-based ECs are prepared, which are grouped on the basis of the concentration of N atoms in the CN “shell”. Each group comprises of both a “pristine” and an “activated” EC; the latter is obtained from the “pristine” EC by a suitable series of treatments (A) devised to improve the ORR performance. The chemical composition of the CN-based ECs is determined by Inductively-Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and microanalysis. The thermal stability under both inert and oxidizing atmospheres is gauged by High-Resolution Thermogravimetric Analysis (HR-TGA). The structure is probed by powder X-ray diffraction, and the morphology is inspected by Scanning Electron Microscopy (SEM) and High-Resolution Transmission Electron Microscopy (HR-TEM). The surface area of the CN-based ECs is determined by nitrogen physisorption techniques, and the surface composition is probed by X-ray Photoelectron Spectroscopy (XPS). The electrochemical performance and reaction mechanism of the CN-based ECs in the ORR is investigated in both acid and alkaline environments by cyclic voltammetry with the Thin-Film Rotating Ring-Disk Electrode setup (CV-TF-RRDE). The influence of the preparation parameters and of the treatments on the physicochemical properties, the ORR performance, and reaction mechanism is studied in detail. In the alkaline environment the FeFe2-CNl 900/CA “core-shell” EC shows a remarkable ORR onset potential of 0.908 V vs. RHE which, with respect to the value of 0.946 V vs. RHE of the Pt/C ref., classifies the proposed materials as very promising “Platinum Group Metal-free” ECs for the ORR.

The development of advanced energy conversion systems characterized by a high efficiency and a low environmental impact is one of the most relevant targets of modern research [1]. As of today, important research efforts are devoted to low-temperature fuel cells (FCs) mounting an acid electrolyte, typically a proton-conducting membrane (e.g., Nafion®). To achieve a performance level compatible with current applications, these systems must adopt electrocatalysts (ECs) with a significant loading of platinum-group metals (PGMs). In conventional low-temperature FCs, most of the PGM loading is typically concentrated at the FC cathode to promote the poor kinetics of the oxygen reduction reaction (ORR), one of the major bottlenecks in FC operation. Very recently, viable OH--conducting membranes were developed [2], opening the possibility to devise efficient anion-exchange membrane fuel cells (AEMFCs). In these systems the ORR takes place in an alkaline environment; accordingly, AEMFCs can adopt “Pt-free” ORR ECs and still achieve a high performance level. In this work, new “Pt-free” ORR ECs are reported; the materials comprise a graphene support “core”, which is covered by a carbon nitride “shell” coordinating the ORR active sites [3]. The proposed materials reap the benefits offered by graphene, including: (i) a high electrical conductivity, minimizing the ohmic losses; and (ii) a low microporosity, to facilitate the mass transport of reactants and products. The carbon nitride “shell” coordinates the bimetallic active sites, which include: (i) a 3d-“active metal” (i.e., Fe, Co, Ni), which bestows most of the ORR performance; and (ii) an oxophilic “co-catalyst” (Sn), which stabilizes the “active metal”and improves the ORR kinetics with a bifunctional mechanism. The chemical composition of the ECs is determined by inductively-coupled plasma atomic emission spectroscopy (ICP-AES) and microanalysis; the thermal stability is studied by high-resolution thermogravimetry (HR-TG); the surface chemical composition is explicated by X-ray photoelectron spectroscopy (XPS); the morphology is elucidated in detail by high-resolution scanning electron microscopy (HR-SEM) and high-resolution transmission electron microscopy (HR-TEM); the porosity is inspected by nitrogen physisorption techniques; the structure is investigated by wide-angle X-ray diffraction (WAXD), electron diffraction and micro-Raman; finally, the ORR performance and mechanism are clarified by means of cyclic voltammetry with the thin-film rotating ring-disk electrode (CV-TF-RRDE) method. The results proved very promising, clearly showing the potential of this family of “Pt-free”, “core-shell” graphene-supported ECs for application at the cathode of AEMFCs. In particular, CV-TF-RRDE measurements in an alkaline environment demonstrated that the best material exhibits an ORR overpotential ca.70 mV higher with respect to a 10 wt.% Pt/C reference (see Figure). References [1] F. Bonaccorso, L. Colombo, G. Yu, M. Stoller, V. Tozzini, A. C. Ferrari, R. S. Ruoff, V. Pellegrini, Science 347, 1246501 (2015). [2] G. A. Giffin, S. Lavina, G. Pace, V. Di Noto, J. Phys. Chem. C 116, 23965 (2012). [3] V. Di Noto, E. Negro, K. Vezzù, F. Bertasi, G. Nawn, The Electrochemical Society Interface, Summer 2015, 63 (2015). Figure 1

The synthesis, physicochemical properties and conductivity mechanism of a family of ionic liquid-based electrolytes for use in secondary Mg batteries are reported. The electrolytes are obtained by dissolving controlled amounts of delta-MgCl2 salt into the ionic liquid (IL) 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF(4)) which acts as a solvent. delta-MgCl2 consists of an inorganic ribbon of Mg atoms covalently bonded together through bridging chlorine atoms. Due to this peculiar structural motif, with respect to the electrolytes based on conventional Mg salts, it is possible to achieve electrolytes of higher Mg concentration. Thus, concatenated anionic complexes bridged via halogen atoms are formed, improving the electrochemical performance of these materials. Electrolytes with a general formula EMImBF(4)/(delta-MgCl2)(f) with f ranging from 0 to 0.117 are obtained. The composition of the obtained materials is determined by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). The properties of these systems are investigated by means of Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and vibrational spectroscopy in both medium (MIR) and far infrared (FIR). Finally, Broadband Electrical Spectroscopy (BES) is carried out with the aim to elucidate the electrical response of the electrolytes in terms of their polarization and relaxation phenomena and to propose a conductivity mechanism. At 20 degrees C the highest conductivity (0.007 S/cm) is observed for the electrolyte with c(Mg) = 0.00454 mol(Mg)/kg(IL). (C) 2016 Elsevier Ltd. All rights reserved.

The numerous potential benefits of incorporating anion-exchange membranes (AEMs), in place of proton-exchange membranes (PEMs), in energy storage and conversion technologies renders their development of fundamental importance for the continued evolution of alternative energy systems. However, the widespread implementation of AEMs is currently plagued by a range of problems including lower conductivity (with respect to PEMs), poor stability, and high cost. This study reports the conversion of polyketone, one of the world's most mass produced and cheap polymers, to a new highly tuneable polymer architecture, functionalized polyketone (FPK), that demonstrates a range of excellent properties rendering it a significant prospect for AEM materials. The thermal, processing, and ion-conducting properties of FPK are governed by the amount and nature of the newly formed N-substituted pyrrole pendant side groups. At 80 °C, the quarternized pyridyl FPK derivative (4MPyrFPK) yields ion-conductivities of 8.6 and 10.5 mS cm-1 in the iodide and hydroxide forms. In addition, the hydroxide form of 4MPyr-FPK demonstrates remarkable stability toward the typically problematic alkaline conditions. No chemical decomposition is observed to the membrane after imbibing it in KOH solution for 72 h, and furthermore, the ion-conductivity is demonstrated to remain constant for at least 30 d at 80 °C.

Understanding the structure–property relationships and the phenomena responsible for ion conduction is one of the keys in the design of novel ionomers with improved properties. In this report, the morphology and the mechanism of ion exchange in a model anion exchange membrane (AEM), poly(vinyl benzyl trimethyl ammonium bromide)-block-poly(methylbutylene) ([PVBTMA][Br]-b-PMB), is investigated with small angle X-ray scattering, high-resolution thermogravimetry, modulated differential scanning calorimetry, dynamic mechanical analysis, and broadband electrical spectroscopy. The hyper-morphology of the material consists of hydrophilic domains characterized by stacked sides of [PVBTMA][Br] which are sandwiched between “spaghetti-like” hydrophobic cylindrical parallel domains of the PMB block. The most important interactions in the hydrophilic domains occur between the dipoles of ammonium bromide ion pairs in the side chains of adjacent chains. A reordering of the ion pair dipoles is responsible for a disorder–order transition (Tδ) at high temperature, observed here for the first time in AEMs, which results in a dramatic decrease of the ionic conductivity. The overall mechanism of long range charge transfer, deduced from a congruent picture of all of the results, involves two distinct ion conduction pathways. In these pathways, hydration and the motion of the ionic side groups are crucial to the conductivity of the AEM. Unlike the typical perfluorinated sulfonated proton-conducting polymer, the segmental motion of the backbone is negligible.

Indigo di- and monoimines can be protonated to form stable salts in which the central C=C bond has isomerized from a trans to cis configuration. Deprotonation of these salts regenerates the neutral trans species. The protonation chemistry of indigo is also explored.

Polybenzimidazole (PBI) has become a popular polymer of choice for the preparation of membranes for potential use in high-temperature proton exchange membrane polymer fuel cells. Phosphoric acid-doped composite membranes of poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] (PBI4N) impregnated with hafnium oxide nanofiller with varying content levels (0-18 wt %) have been prepared. The structureproperty relationships of both the undoped and acid-doped composite membranes are studied using thermogravimetric analysis, modulated differential scanning calorimetry, dynamic mechanical analysis, wide-angle X-ray scattering, infrared spectroscopy, and broadband electrical spectroscopy. Results indicate that the presence of nanofiller improves the thermal and mechanical properties of the undoped membranes and facilitates a greater level of acid uptake. The degree of acid dissociation within the acid-doped membranes is found to increase with increasing nanofiller content. This results in a conductivity, at 215 degrees C and a nanofiller level x = 0.04, of 9.0 x 10(-2) S cm(-1) for [PBI4N(HfO2)(x)](H3PO4)(y). This renders nanocomposite membranes of this type as good candidates for use in high temperature proton exchange membrane fuel cells (HT-PEMFCs).

Recent advances in technological fields such as portable electronic devices, automotive, load levelling and peak shaving for the power grid applications, as well as other specific low and high temperature applications, have resulted in an urgent need to develop new and improved energy conversion and storage systems.1 Magnesium secondary batteries, first proposed in the late 1990s,2,3 demonstrate intrinsic fundamental advantages over other competing technologies i.e., Li secondary batteries, and are therefore promising candidates for energy conversion and storage. Early Mg secondary batteries comprised of a metallic magnesium anode, a composite cathode and a polymer electrolyte based on polyethylene glycol incorporating an innovative δ-MgCl2 salt.4,5 Subsequent electrolytes based on Grignard and other organo-Mg compounds have also been explored,6 and were shown to exhibit good Mg deposition/stripping. Nevertheless, these electrolytes suffer from several drawbacks associated with their chemical stability in ethereal-based solvents, which are characterized by high vapour pressure and flammability. In order to overcome these drawbacks, the use of ionic liquids (ILs) as a solvent for stable Mg-ion source precursors is appealing in order to obtain electrolytes with a high chemical inertia, a wide electrochemical stability window, a low volatility and negligible flammability.7 Here we present a new room temperature ionic liquid synthesized by reacting 1-ethyl-3 methylimidazolium iodide with aluminium iodide. δ-MgI2 8 is used as the magnesium source to obtain a family of Mg2+ conducting electrolytes with the general formula [EMImI/(AlI3)m]/(δ-MgI2)n. δ-MgI2 which is a highly disordered form of MgI2 and synthesized by reacting metallic Mg with n-iodobutane. Similar to the previously described δ-MgCl2,9 δ-MgI2 forms concatenated polymer chain complexes with aluminium through iodine bridging atoms. The chemical composition of the samples was determined by ICP-AES and microanalysis. Their thermal stability and transitions were studied by differential scanning calorimetry (DSC). The applicability of the [EMImI/(AlI3)m]/(δ-MgI2)n electrolytes in prototype cells was evaluated by studying the conductivity of the materials as well as the electrochemical performance in terms of Mg deposition/stripping, coulombic efficiency, and exchange current density. Results of the deposition/stripping performance for a selected concentration are shown in Figure 1. References (1) Armand, M.; Tarascon, J.-M. Nature 2008, 451, 652. (2) Di Noto, V.; Fauri, M. Batterie primarie (non ricaricabili) e secondarie (ricaricabili) a base di elettroliti polimerici basati su ioni magnesio. PD99A000179, 1999. (3) Di Noto, V.; Fauri, M. Magnesium-based Primary (Non Rechargeable) and Secondary (Rechargeable) Batteries. PCT/EP00/07221, 2000. (4) Di Noto, V.; Lavina, S.; Longo, D.; Vidali, M. Electrochim. Acta 1998, 43, 1225. (5) Di Noto, V.; Marigo, A.; Viviani, M.; Marega, C.; Bresadola, S.; Zannetti, R. Makromol. Chem. 1992, 193, 123. (6) Liebenow, C.; Yang, Z.; Lobitz, P. Electrochem. Commun. 2000, 2, 641. (7) Armand, M.; Endres, F.; MacFarlane, D. R.; Ohno, H.; Scrosati, B. Nat. Mater. 2009, 8, 621. (8) Vittadello, M.; Waxman, D. I.; Sideris, P. J.; Gan, Z.; Vezzù K.; Negro, E.; Safari, A.; Greenbaum, S. G.; Di Noto, V. Electrochim. Acta 2011, 57, 112. (9) Vittadello, M.; Stallworth, P. E.; Alamgir, F. M.; Suarez, S.; Abbrent, S.; Drain, C. M.; Di Noto, V.; Greenbaum, S. G. Inorg. Chim. Acta 2006, 359, 2513. Figure 1

A poly(ethylene glycol) 400 (PEG400) matrix doped with different amounts of a fluorinated Fe 2 O 3 -based nanofiller (LiFI) featuring a Li + -functionalised surface gives rise to nanocomposite polymer electrolytes (nCPEs) that demonstrate single-ion conduction. A family of nCPEs with general formula [PEG400/(LiFI) y ] and y = n Fe /n PEG400 ranging from 0 to 8.15 are prepared; they are characterized by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), High-Resolution Thermogravimetric Analysis (HR-TGA), Differential Scanning Calorimetry (DSC), and Fourier-transform vibrational spectroscopy in both the medium (MIR) and far (FIR) infrared. The Li + transference number, t Li+ ,is determined and Broadband Electrical Spectroscopy (BES) is used to elucidate the electrical response of the materials in terms of polarization and relaxation events. The combination of the information obtained by all the aforementioned techniques enables us to present a possible conduction mechanism for these nCPEs single-ion conducting systems.

F uel cells (FCs) operating at low temperatures (T < 200 °C) show several very attractive features, including: (a) relatively simple assembly; (b) good compatibility with the environment; and (c) very high efficiency with respect to internal combustion engines. However, the full potential of low-temperature FCs can only be achieved by addressing a number of crucial issues involved in their operation. One of the most important bottlenecks is represented by the slow kinetics of the oxygen reduction reaction (ORR).1 Typical examples of low-temperature fuel cells include proton exchange membrane fuel cells (PEMFCs) and anion-exchange membrane fuel cells (AEMFCs).1 To achieve energy conversion efficiencies and power densities compatible with applications, all these devices require suitable ORR electrocatalysts (ECs) to minimize cathode polarization losses. Ideally, ORR ECs should possess the following features

In recent years, anion exchange membrane fuel cells (AEMFCs) have been extensively studied owing to significant advantages over their proton exchange membrane fuel cell (PEMFC) counterparts [1]. The possibility to adopt electrocatalysts that do not comprise of precious metals as well as diminished poisoning effects are among the most relevant reasons for which AEMFCs are believed to be advantageous. However, AEMFCs do suffer from some drawbacks, specifically concerned with the anion exchange membrane (AEM) which is responsible for the selective migration of OH- anions from the cathode to the anode, and is one of the most critical components of the entire AEMFC. In particular, with respect to the proton exchange membranes used in PEMFCs, AEMs typically exhibit a lower ionic conductivity and an inferior chemical stability, the latter typically associated with the degradation of anion-exchange functionalities. For these reasons, it is very important to elucidate the details of the complex interplay between the nanostructure and the ion conductivity mechanism of the AEMs. Over the last 30 years it has been demonstrated that conductivity in ion-conducting materials occurs via a number of different processes including: (a) the migration of ions between coordination sites [2-5]; and (b) the diffusion of conformational states of the host matrix (segmental motion). [2-5]. In ion-conducting membranes the long-range charge migration is often correlated with the dielectric relaxation modes of the polymeric chains; the latter are typically associated with the fluctuation of: a) the main backbone chain bearing permanent dipole moments; b) side chains; or c) functional groups involved in ion-dipole interactions. The key technique to investigate the interplay between structure and conductivity of ion-conducting materials is Broadband Electrical Spectroscopy (BES). Here we present several case studies of AEMs paying particular attention to their thermal stability and the thermomechanical properties. BES is then adopted to study the electrical response of each material in terms of polarizations and relaxation phenomena. The results allow us to: (a) suggest a comprehensive model capable to rationalize the long-range charge transfer mechanism in AEMs; and (b) clarify how the chemical composition and nanostructure of the materials is influencing the coordination of mobile species. Acknowledgements The authors thank the StrategicProject “From materials for Membrane electrode Assemblies to electric Energy conversion and SToRAge devices” (MAESTRA) of the University of Padova for funding this activity. References [1] Polymer Electrolytes: Fundamentals and Applications; Sequeira, C.; Santos, D., Eds.; Woodhead Publishing Limited, Oxford, 2010. [2] Di Noto, V. J. Phys. Chem. B, 104 (2000) 10116. [3] Di Noto, V.; Vittadello, M.; Lavina, S.; Fauri, M.; Biscazzo, S. J. Phys. Chem. B, 105 (2001) 4584. [4] Di Noto, V. J. Phys. Chem. B, 106 (2002) 11139. [5] Di Noto, V.; Vittadello, M.; Greenbaum, S. G.; Suarez, S.; Kano, K.; Furukawa, T. J. Phys. Chem. B, 108 (2004) 18832.

The operation of proton exchange fuel cells (PEMFCs) is bottlenecked by the sluggishness of the oxygen reduction reaction (ORR) [1]. Accordingly, the development of advanced electrocatalysts (ECs) capable to promote the ORR kinetics is one of the main goals of the research. It is further highlighted that, as of today, the only ORR ECs capable to provide PEMFCs with a performance level compatible with applications require a high loading of strategic elements such as platinum-group metals (PGMs), raising critical issues associated with supply shortages and high costs [1]. This work addresses the above points by the development of innovative ECs characterized by the following features: (i) a low loading of PGMs; (ii) an improved ORR activity in comparison with conventional state-of-the-art ECs [2]; (iii) a “core-shell” morphology. In the proposed ECs the “core” support exhibits a hierarchical structure including the following constituents: (i) graphene flakes, to exploit the benefits associated with the large specific surface area and high electron mobility of graphene [3-6]; (ii) carbon black nanoparticles, to further promote the mass and charge transfer processes of the ECs; and (iii) copper nanoparticles, which are introduced as a sacrificial component modulating the EC morphology and the chemical composition of ORR active sites. The hierarchical “core” support is covered by a carbon nitride “shell”, providing “coordination nests” that embed the ORR active sites [7]. The latter are based on a very low loading of Pt (ca. 3 wt% of the EC) and also include Ni and Cu as “co-catalysts”. The proposed L-PGM ECs are obtained customizing the synthetic protocol devised in our research group [7]. In this work, the final ECs are obtained after a post-synthesis activation process carried out by electrochemical cycling, that plays a crucial role to modulate the physicochemical properties and the morphology. Preliminary results indicate that the proposed approach is promising, as the proposed L-PGM ECs exhibit an improved specific and mass activity in comparison with the state of the art (see Figure). The assay of the metals in the L-PGM ECs is evaluated by inductively-coupled plasma atomic emission spectroscopy (ICP-AES). Vibrational spectroscopies (e.g., confocal micro-Raman) and wide-angle X-ray diffraction (WAXD) are adopted to probe the structure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM), both conventional and at high resolution, are used to study the morphology. Cyclic voltammetry with the rotating ring-disk electrode method (CV-TF-RRDE) investigates the electrochemical performance and ORR reaction mechanism. Finally, the fuel cell performance in operating conditions is tested on PEMFC prototypes including the proposed L-PGM ECs at the cathode. Acknowledgements This work was funded by the Strategic Project of the University of Padova “From Materials for Membrane-Electrode Assemblies to Energy Conversion and Storage Devices – MAESTRA”. The research leading to these results has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement n°696656. REFERENCES [1] I. Katsounaros, S. Cherevko, A. R. Zeradjanin, K. J. J. Mayrhofer, Angew. Chem. Int. Ed., 53, 102 (2014). [2] J. Zhang, Front. Energy, 5, 137 (2011). [3] S. Sharma, B. G. Pollet, J. Power Sources, 208, 96 (2012). [4] M. Liu, R. Zhang, W. Chen, Chem. Rev., 114, 5117 (2014). [5] A. C. Ferrari, F. Bonaccorso, V. Fal’ko et al., Nanoscale, 7, 4587 (2015). [6] J. H. Chen, C. Jang, S. Xiao, M. Ishigami, M. S. Fuhrer, Nature Nanotech., 3, 206 (2008). [7] V. Di Noto, E. Negro, K. Vezzù, F. Bertasi, G. Nawn, The Electrochemical Society Interface, Summer 2015, 59 (2015). Figure 1

The charge transfer mechanisms of ion conducting polymer materials (ICPMs) is of crucial importance both for fundamental research and for a host of practical applications, including primary and secondary batteries, fuel cells, dye-sensitized solar cells, supercapacitors and sensors. A wide variety of ICPMs has been proposed, based on: (a) different families of polymer electrolytes; (b) ionic liquids (ILs); and (c) classical ion-conducting ceramics. In these materials, the long-range charge transfer events take place owing to complex processes, which involve several possible relaxation phenomena, such as: (a) ion hopping events between ion coordination sites; (b) relaxation modes of the host matrix; and (c) polarization effects occurring at the interfaces between the different domains characterizing the materials. Broadband electrical spectroscopy (BES) is a powerful tool for the accurate investigation of the roles played by electrical relaxation events in the charge transfer processes. Indeed, BES allows to carefully detect the fundamental relaxations governing the long-range charge transfer mechanisms and to correlate them to the morphology of ion-conducting materials. This presentation overviews results of the application of BES in the study of the charge transfer mechanisms of a variety of ICMs, including: (a) polymer electrolytes based on alkaline and alkaline-earth ions; (b) pristine and hybrid inorganic-organic proton-conducting and anion-conducting membranes. The general phenomena and the fundamental theory underlying the interpretation of the events characterizing the electric response of the materials is also described. Finally, the models adopted for the interpretation of conductivity mechanisms are described and a unified conductivity mechanism is proposed.

Owing to the numerous benefits obtained when operating proton exchange membrane fuel cells at elevated temperature (>100 °C), the development of thermally stable proton exchange membranes that demonstrate conductivity under anhydrous conditions remains a significant goal for fuel cell technology. This paper presents composite membranes consisting of poly[2,2?-(m-phenylene)-5,5?-bibenzimidazole] (PBI4N) impregnated with a ZrO2 nanofiller of varying content (ranging from 0 to 22 wt %). The structure-property relationships of the acid-doped and undoped composite membranes have been studied using thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, wide-angle X-ray scattering, infrared spectroscopy, and broadband electrical spectroscopy. Results indicate that the level of nanofiller has a significant effect on the membrane properties. From 0 to 8 wt %, the acid uptake as well as the thermal and mechanical properties of the membrane increase. As the nanofiller level is increased from 8 to 22 wt % the opposite effect is observed. At 185 °C, the ionic conductivity of [PBI4N(ZrO2)0.231](H3PO4)13 is found to be 1.04×10-1 S cm-1. This renders membranes of this type promising candidates for use in high-temperature proton exchange membrane fuel cells.

Anion-exchange membrane fuel cells (AEMFCs) provide significant advantages over their proton-exchange membrane counterparts. In the alkaline environment, the oxygen reduction reaction (ORR) is more facile, there is diminished fuel crossover, and a greater flexibility regarding fuel and catalyst choice. The membrane at the heart of AEMFCs not only facilitates the ion exchange but also separates the fuel feedstocks and acts as a support for the membrane-electrode assembly (MEA). However, to date there are still no membrane materials that satisfy all the needs (long-term stability in alkaline environment, high ionic conductivity, low swelling and good structural integrity) for use in AEMFCs and this remains one of the larger obstacles for further AEMFC development. The amination and subsequent quarternisation of polyketone leads to a new family of ionomers containing N-substituted pyrrole moieties. The degree of amination can be controlled by manipulating reaction conditions, allowing the composition and resulting structural properties of the polymer to be tuned. Membrane fabrication results in thermally stable (TD > 250 oC), structurally robust polymer electrolytes that exhibit ionic conductivity ( > 10-3 S cm-1). These new solid-state ion conducting materials have the potential to be used in a variety of applications including AEMFCs. Here we present an in-depth study focusing on the structure-property relationships of this new polypyrrole/polyketone polymer. A variety of analytical techniques are used to probe the thermal and structural properties of the polymers, these include high-resolution thermogravimetric analysis, modulated differential scanning calorimetry, dynamic mechanical analysis, vibrational, NMR and UV-Vis spectroscopies. In addition, broadband electrical spectroscopy is used to gauge the interplay between the structural properties and electrical response. Figure 1

A critical roadblock toward practical Mg-based energy storage technologies is the lack of efficient electrolytes that are safe and electrochemically stable.[1] Despite their excellent electrochemical performance existing electrolytes based on ethereal solvents and organomagnesium compounds[2][3] are inadequate for meeting the needs of functional devices in portable electronics and transportation applications. It was recently shown[4][5][6] that haloaluminate ionic liquids (ILs) can provide a viable alternative to conventional electrolytes due to their low volatility, negligible flammability and good electrochemical performance. Despite of this, IL-based electrolytes usually show a narrow electrochemical stability window, which limits their use with high voltage cathode materials.[7] Furthermore, in the case of IL-based electrolytes in order to improve their performance, several issues[4][8] should be addressed such as: a) a fundamental understanding of the relation between Mg-ion speciation and the long-range charge transfer mechanism; b) SEI structure and formation; and c) long-term performance. Following this, here we are proposing a new high-performing electrolyte based on 1-Butyl-1-Methylpyrrolidinium chloride (BMPyCl) doped with AlCl3 and highly amorphous δ-MgCl2. The chemical composition of the samples is determined by ICP-AES and microanalysis. The structure and interactions are investigated with vibrational spectroscopies while the thermal stability and transitions are studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) respectively. In addition, the applicability of the [BMePyCl/(AlCl3)m]/(δ-MgCl2)n electrolytes in prototype cells is evaluated by studying the conductivity as well as the electrochemical performance of the materials. References [1] J. Muldoon, C.B. Bucur, A.G. Oliver, T. Sugimoto, M. Matsui, H.S. Kim, et al., Electrolyte roadblocks to a magnesium rechargeable battery, Energy Environ. Sci. 5 (2012) 5941–5950. [2] P. Saha, M.K. Datta, O.I. Velikokhatnyi, A. Manivannan, D. Alman, P.N. Kumta, Rechargeable magnesium battery: Current status and key challenges for the future, Prog. Mater. Sci. 66 (2014) 1–86. [3] J. Muldoon, C.B. Bucur, T. Gregory, Quest for Nonaqueous Multivalent Secondary Batteries: Magnesium and Beyond, Chem. Rev. 114 (2014) 11683–11720. [4] F. Bertasi, C. Hettige, F. Sepehr, X. Bogle, G. Pagot, K. Vezzù, et al., A Key concept in Magnesium Secondary Battery Electrolytes., ChemSusChem. 8 (2015) 3069–76. [5] F. Bertasi, C. Hettige, S.G. Greenbaum, M. Vittadello, V. Di Noto, Ionic Liquids as Electrolytes for Primary and Secondary Batteries, US Patent App. No. 61/900522, 2013. [6] F. Bertasi, C. Hettige, S.G. Greenbaum, M. Vittadello, V. Di Noto, Ionic Liquid Comprising Alkaline Earth Metal, PCT Patent App. No. WO2015/069871, 2014. [7] F. Bertasi, K. Vezzù, E. Negro, G. Pagot, G. Nawn, J. He, et al., A New Iodoaluminate Ionic Liquid for Secondary Magnesium Batteries, in: 227 ECS Meet., 2015. [8] M. Piccolo, G.A. Giffin, K. Vezzù, F. Bertasi, P. Alotto, M. Guarnieri, et al., Molecular Relaxations in Magnesium Polymer Electrolytes via GHz Broadband Electrical Spectroscopy, ChemSusChem. 6 (2013) 2157–2160.

Nowadays, the rapid development in portable electronics, load leveling/peak shaving for the power grid and electric automotive, requires significant progress in high voltage and high capacity storage systems [1,2]. Lithium batteries are, to date, the most promising systems that can sustain this demand [3]; they have high specific energy, high efficiency and a long lifespan [4]. Lithium cobalt oxide (LiCoO2 ) based cathode materials currently dominate the market [5], but, due to a low working potential (3.0 – 4.0 V vs. Li) and to a high cost and toxicity, there is a broad scope for the development of new cathodic materials [6]. Lithium-transition metal-phosphates (LiMPO4 , M=Co, Fe, Mn or Ni) show very good performance: their olivine structure with a 2D framework of crossed tunnels allows the insertion and de-insertion of lithium ions during the discharge/charge of the battery [7]. The highest specific capacity is reached by lithium iron phosphate (LiFePO4 ), but at low potential, while the highest working potential can be obtained using lithium cobalt phosphate (LiCoPO4 ) or lithium nickel phosphate (LiNiPO4 ), however, the lifespan and the specific capacity become very low [8-10]. In this work we describe the synthesis and the characterization of a new family of high voltage cathodic materials based on lithium-transition metal mixture-phosphates of iron, nickel and cobalt, in order to best take advantage of all the positive characteristics of each element presents in the structure (high voltage and high capacity) [11]. Five materials have been produced, varying the Ni/Co molar ratio; the effect of different degrees of Co and Ni doping on structure, morphology and electrochemical properties have been thoroughly studied. The stoichiometry is evaluated using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), the thermal stability is investigated by High Resolution – Thermo Gravimetric Analyses (HR-TGA), morphology and size distribution are characterized by Field Emission - Scanning Electron Microscopy (FE-SEM) and High-Resolution Transmission Electron Microscopy (HR-TEM) (see Figure 1); the structure is examined by powder X-Ray Diffraction (XRD) as well as variety of IR spectroscopy techniques. Electrochemical characterization is achieved by Cyclic Voltammetry (CV) and charge/discharge tests (see Figure 2). Indeed, the proposed materials are good cathodic candidates for the development of high voltage lithium batteries: the best of our materials LFNCP0.61 showed a specific capacity and a specific energy of 125 mAh∙g-1 and 560 mWh∙g-1, respectively. Acknowledgements The authors thank, a) the strategic project “From Materials for membrane electrode Assemblies to electric Energy conversion and SToRAge devices” (MAESTRA) of the University of Padova for funding this study; b) the “Centro studi di economia e tecnica dell’energia Giorgio Levi Cases” for grants to G.P. and E.N. References 1 M. Armand and J. M. Tarascon Nature 451, 652-657, (2008). 2 B. Dunn, H. Kamath and J. M. Tarascon Science 334, 928-935, (2011). 3 V. Di Noto, T. A. Zawodzinski, A. M. Herring, G. A. Giffin, E. Negro and S. Lavina Int. J. Hydrogen Energy 37, 6120-6131, (2012). 4 B. Scrosati and J. Garche J. Power Sources 195, 2419-2430, (2010). 5 K. Zaghib, A. Mauger, H. Groult, J. B. Goodenough and C. M. Julien Mater. 6, 1028-1049, (2013). 6 K. Zaghib, J. Dubé, A. Dallaire, K. Galoustov, A. Guerfi, M. Ramanathan, A. Benmayza, J. Prakash, A. Mauger and C. M. Julien J. Power Sources 219, 36-44, (2012). 7 V. A. Streltsov, E. L. Belokoneva, V. G. Tsirelson and N. K. Hansen Acta Crystallogr., Sect. B: Struct. Sci. B49, 147-153, (1993). 8 N. N. Bramnik, K. G. Bramnik, T. Buhrmester, C. Baehtz, H. Ehrenberg and H. Fuess J. Solid State Electrochem. 8, 558-564, (2004). 9 A. K. Padhi, K. S. Nanjundaswamy and J. B. Goodenough J. Electrochem. Soc. 144, 1188-1194, (1997). 10 J. Wolfenstine and J. Allen J. Power Sources 142, 389-390, (2005). 11 G. Pagot, F. Bertasi, G. Nawn, E. Negro, G. Carraro, D. Barreca, C. Maccato, S. Polizzi and V. Di Noto Adv. Funct. Mater. 25, 4032-4037, (2015). Figure 1

Reactions of indigo with a variety of substituted anilines produce the corresponding indigo diimines ("Nindigos") in good yields. Nindigo coordination complexes are subsequently prepared by reactions of the Nindigo ligands with Pd(hfac)(2). In most cases, binuclear complexes are obtained in which the deprotonated Nindigo bridges two Pd(hfac) moieties in the expected bis-bidentate binding mode. When the Nindigo possesses bulky substituents on the imine (mesityl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, etc.), mononuclear Pf(hfac) complexes are obtained in which the Nindigo core has isomerized from a trans- to a cis-alkene; in these structures, the palladium is bound to the cis-Nindigo ligand at the two indole nitrogen atoms; the remaining proton is bound between the imine nitrogen atoms. The palladium complexes possess intense electronic absorption bands [near 920 nm for the binuclear complexes and 820 nm for the mononuclear cis-Nindigo complexes; extinction coefficients are (1.0-2.0) × 10(4) M(-1) cm(-1)] that are ligand-centered (π-π*) transitions. Cyclic voltammetry investigations reveal multiple redox events that are also ligand-centered in origin. All of the palladium complexes can be reversibly oxidized in two sequential one-electron steps; the binuclear complexes are reduced in a two-electron process whose reversibility depends on the Nindigo ligand substituent; the mononuclear palladium species show two one-electron reductions, only the first of which is quasi-reversible.

Nowadays, the rapid development in portable electronics, load leveling/peak shaving for the power grid and electric automotive requires significant progress in high-voltage and high-capacity storage systems [1, 2]. Lithium batteries are, to date, the most promising systems that can sustain this demand [3]; they have high specific energy, high efficiency and a long lifespan [4]. Lithium cobalt oxide (LiCoO2 ) based cathode materials currently dominate the market [5] but, due to a low working potential (3.0 – 4.0 V vs. Li) and a high cost and toxicity, there is a broad scope for the development of new cathodic materials [6]. Lithium-transition metal-phosphates (LiMPO4 , M=Co, Fe, Mn or Ni) show very good performance: their olivine structure with a 2D framework of crossed tunnels allows the insertion and de-insertion of lithium ions during the discharge/charge of the battery [7]. Lithium iron phosphate (LiFePO4 ) affords the highest specific capacity, albeit at a low potential. On the other hand, lithium cobalt phosphate (LiCoPO4 ) or lithium nickel phosphate (LiNiPO4 ) give rise to higher working potentials, but the lifespan and the specific capacity become very low [8-10]. In this work we describe the synthesis and the characterization of a new family of high-voltage cathodic materials based on lithium-transition metal mixture-phosphates of iron, nickel and cobalt, in order to best take advantage of all the positive characteristics of each element present in the structure (high voltage and high capacity) [11]. Five materials have been produced, varying the Ni/Co molar ratio; the effect of different degrees of Co and Ni doping on structure, morphology and electrochemical properties have been thoroughly studied. The stoichiometry is evaluated using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES), the thermal stability is investigated by High Resolution – Thermo Gravimetric Analyses (HR-TGA), morphology and size distribution are characterized by Field Emission - Scanning Electron Microscopy (FE-SEM) and High-Resolution Transmission Electron Microscopy (HR-TEM) (see Figure 1); the structure is examined by powder X-Ray Diffraction (XRD) as well as a variety of IR spectroscopy techniques. Electrochemical characterization is carried out by Cyclic Voltammetry (CV) and charge/discharge tests (see Figure 2). Indeed, the proposed materials are good cathodic candidates for the development of high-voltage lithium batteries: the best of our materials, LFNCP0.61, showed a specific capacity and a specific energy of 125 mAh∙g-1 and 560 mWh∙g-1, respectively. Acknowledgements The authors thank: (a) the strategic project “From Materials for membrane electrode Assemblies to electric Energy conversion and SToRAge devices” (MAESTRA) of the University of Padova for funding this study; and (b) the “Centro Studi di Economia e Tecnica dell’Energia Giorgio Levi Cases” for grants to G.P. and E.N. REFERENCES 1. M. Armand, J.M. Tarascon, Nature 451, 652 (2008). 2. B. Dunn, H. Kamath, J.M. Tarascon, Science 334, 928 (2011). 3. V. Di Noto, T.A. Zawodzinski, A.M. Herring, et al., Int. J. Hydrogen Energy 37, 6120 (2012). 4. B. Scrosati, J. Garche, J. Power Sources 195, 2419 (2010). 5. K. Zaghib, A. Mauger, H. Groult, et al., Mater. 6, 1028 (2013). 6. K. Zaghib, J. Dubé, A. Dallaire, et al., J. Power Sources 219, 36 (2012). 7. V.A. Streltsov, E.L. Belokoneva, V.G. Tsirelson, et al., Acta Crystallogr., Sect. B: Struct. Sci. B49, 147 (1993). 8. N.N. Bramnik, K.G. Bramnik, T. Buhrmester, et al., J. Solid State Electrochem. 8, 558 (2004). 9. A.K. Padhi, K.S. Nanjundaswamy, J.B. Goodenough, J. Electrochem. Soc. 144, 1188 (1997). 10. J. Wolfenstine, J. Allen, J. Power Sources 142, 389 (2005). 11. G. Pagot, F. Bertasi, G. Nawn, et al., Adv. Funct. Mater. (2015). In press. Figure 1