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Molten salts are one of the promising alternative classes of new materials for electrochemical processing. They have high chemical stability and offer much wider electrochemical window than conventional aqueous media. This enables various electrochemical reactions to be conducted without decomposing background media. In addition, the high operation temperature of molten salt boosts the mass transfer of reactant of electrochemical reaction, so that the processing time is shortened. Owing to such advantages, the molten salt media have intensively dealt with the electrowinning of metal and electrochemical separation processes. However, knowing the chemical behavior of electrodes during such processes is crucial to understanding the mechanism of electrochemical reactions that occur during the process. One of the most powerful methods of examining the system is to monitor the visual status of electrodes in real time while the electrochemical process is running. However, due to some practical limitations, it has rarely been applied to the molten salt electrochemical system. In the present work, the real-time monitoring system for molten LiCl-KCl eutectic salt medium is set up. Instead of an optically opaque ceramic crucible, a cylindrical quartz tube is chosen for the electrochemical cell of our experimental system. With four optically accessible quartz windows mounted on the electrical furnace, a commercially available CMOS camera can be installed externally to monitor the molten salt system without any special modifications. Real-time monitoring was carried out to investigate the electrode behavior in various electrochemical systems. First, the deposition behavior of cobalt in molten CoCl2-LiCl-KCl system (1wt% CoCl2) is compared on a tungsten working electrode. As shown in Figure 1, there is a clear morphological structural difference in the cobalt deposit between the galvanostatic and the potentiostatic electrodeposition. While the metallic cobalt was deposited evenly on the surface of the working electrode by galvanostatic electrodeposition, rapid growth of the dendritic structure was observed using the potentiostatic electrodeposition. This suggests that the structural properties of deposits can vary significantly due to the nature of the electrodeposition methods. In electrochemical experiments in molten salt system that do not produce solid phase products, it is difficult to elaborately understand the behavior of chemical species during the experiment. However, real-time monitoring enables noteworthy observation from these experiments. During the galvanostatic lithium reduction in the molten LiCl-KCl system, the liquefied metallic lithium formed the oval bulge on the surface of the tungsten working electrode. At the same time, the unknown indigo-colored flow was observed on the surface of the deposited metallic lithium. The clear mechanism remains to be explored, but it appears to be related to the re-oxidization of metallic lithium to Li(I) ions. In the molten ZrCl4-LiCl-KCl system (1wt% ZrCl4) with tungsten working electrode, the reduction of Zr(IV) ions to Zr(III) ions during the potentiostatic electroreduction was visualized and identified by the formation of brown-colored flow near the surface of the working electrode. This confirms the result of our previous work and suggests that Zr(IV) is reduced to Zr(III) with a brown color in the first step of CV [1]. Furthermore, with the video signal from the CMOS camera to the PC that controls the potentiostat, the visual changes can be synced with the measured current or potential during the experiment. This enables us to compare the visualized morphological properties on the surface of the working electrode under different applied potential conditions during the CV experiment (Figure 2). [1] H. L. Cha, J.-I. Yun, Electrochem. Commun. 84, 86 (2017) Figure 1

This study presents the electrochemical behaviors and thermodynamic properties of Ce on liquid Bi, Sn, and Zn electrodes in molten LiCl-KCl eutectic salt. First, the Ce-metal binary systems on the solid tungsten electrode were investigated to determine the formation of Ce-metal intermetallic compounds during the electrowinning process. In these experiments, the formation of five Ce–Bi intermetallic compounds, eight Ce–Sn intermetallic compounds, and nine Ce–Zn intermetallic compounds was confirmed from the oxidation peaks of cyclic voltammetry. The standard Gibbs free energy of formation of each intermetallic compound was calculated from plateaus of the open-circuit chronopotentiometry. Subsequently, the electrochemical behaviors of Ce were investigated on liquid Bi, Sn, and Zn electrodes using cyclic voltammetry. In particular, while the reduction potentials of Li and Ce were too close to differentiate on the liquid Bi and Sn electrodes, they were not on the liquid Zn electrode. Peak potentials from cyclic voltammetry were utilized to calculate the activity coefficients of Ce in the liquid Bi, Sn, and Zn electrodes, which were 3.16 × 10−14, 1.82 × 10−12, and 9.05 × 10−10, respectively.

Recently, lithium-ion batteries (LIBs) have been applied to large-scale devices such as electric vehicles and energy storage systems (ESSs), requiring high energy density and long cycle life. The use of organic electrolytes in lithium ion batteries in such large-scale devices has some safety issues. Organic electrolytes have a high ionic conductivity, but there are many risks of leakage, explosion and ignition due to the decomposition reaction of the electrolyte. As a promising solution to this issues, the use of a solid electrolyte have been proposed. In contrast to organic-based liquid electrolytes, all-solid-state lithium batteries (ASLBs) with a solid electrolyte are considered safe because of their non-flammability. These solid electrolytes have the advantages of high stability and high energy density, but they have a disadvantage of very low ionic conductivity at room temperature. In this work, we prepared sheet-type Li6PS5Cl-infiltrated electrode that has high capacity, even though it has high loading value. We propose two methods to ensure that SE materials are evenly distributed and sufficiently infiltrated into the porous structures of LIB electrode. First, we aimed to reveal the effects of solid electrolyte solution vaporization on the solid electrolyte content in the thick electrode for ASSBs. The performance of the cells at different temperatures were compared. Elevated temperature of SE solution arrive at vaporization point and it result in molecular motion, and it makes more LPSCl infiltrated into electrode. The NCM622 electrode infiltrated LPSCl at 90oC show reversible capacity of 177mAh/g (5.5mg/cm2) and 136mAh/g (17mg/cm2) at 0.05C, 55oC. We also prepared three different active materials having different particle size. The porous electrode which is made by mixing different sized active materials(DS-AM) absorbs SE solution. This absorb effects explain the capillary phenomena. The mixed DS-AM electrode demonstrated higher capacity than non-mixed DS-AM electrodes due to the improved ion transport path.

Multi-mode atomic force microscopy (AFM) was used to differentiate between Nafion® and electrospun composite nanofiber membranes. The results of this experiment will guide the design of new class of proton exchange membranes (PEM). Characterizing the electrospun composite nanofiber membranes will allow us to identify properties that are ideal for the next generation PEM. Engineering the proton conducting membrane for a PEM fuel cell that allows protons and inhibits other species to cross is vital to its long-term operation. When species other than protons are allowed to cross a PEM, issues arise in the form of electrode flooding, adverse chemical reactions, and reduced fuel cell efficiency.

Regenerative hydrogen bromine (H2/Br2) fuel cells, which utilize a membrane-electrode-assembly (MEA) with a polymeric cation exchange membrane, are an attractive energy storage system. In this paper, dual nanofiber electrospun composite proton exchange membranes were created by electrospinning two polymers: perfluorosulfonic acid (Nafion®) and polyphenylsulfone (PPSU). The dual nanofiber mat was processed into Nafion nanofibers embedded in PPSU. For this regenerative H2/Br2 fuel cell system, proton conductivity, the Br2/Br3- diffusion coefficient and permeability in composite membranes with different Nafion volume fractions are presented and discussed.

Innovation in the design of electrolyte materials is crucial for realizing next-generation electrochemical energy storage devices such as Li–S batteries. The theoretical capacity of the S cathode is 10 times higher than that of conventional cathode materials used in current Li–ion batteries. However, Li–S batteries suffer from the dissolution of lithium polysulfides, which are formed by the redox reaction at the S cathode. Herein, we present simple solvate ionic liquids, glyme–Li salt molten complexes, as excellent electrolyte candidates because they greatly suppress the dissolution of lithium polysulfides. The molten complexes do not readily dissolve other ionic solutes, which leads to the stable operation of the Li–S battery over more than 400 cycles with discharge capacities higher than 700 mAh g-sulfur−1 and with coulombic efficiencies higher than 98% throughout the cycles. Such high performance has not been realized to the best of our knowledge. Furthermore, the addition of a nonflammable fluorinated solvent, which does not break the solvate structure of the glyme–Li salt molten complexes, greatly enhances the power density of the Li–S battery. The strategic design of electrolyte properties provides opportunities for the development of new electrochemical devices with many different electrode materials.

Recently, lithium-ion batteries (LIBs) have been applied to large-scale devices such as electric vehicles and energy storage systems (ESSs), requiring high energy density and long cycle life. The use of organic electrolytes in lithium ion batteries in such large-scale devices has some safety issues. Organic electrolytes have a high ionic conductivity, but there are many risks of leakage, explosion and ignition due to the decomposition reaction of the electrolyte. As a promising solution to this issues, the use of a solid electrolyte have been proposed. In contrast to organic-based liquid electrolytes, all-solid-state lithium batteries (ASLBs) with a solid electrolyte are considered safe because of their non-flammability. These solid electrolytes have the advantages of high stability and high energy density, but they have a disadvantage of very low ionic conductivity at room temperature. In previous studies, PEO-based membrane is available in a free form for all solid state battery designs, but it has very low ionic conductivity (10-6-10-8 S/cm) at room temperature because of their very low ion mobility below their melting point (~ 60°C). The PEO-based membrane with inorganic filler increases ion diffusion or mobility by stabilizing the highly conductive amorphous phase. In our previous research, the composite membrane was prepared by incorporating tetragonal Li7La3Zr2O12 (LLZO) solid electrolyte in a polyethylene oxide (PEO) matrix. LLZO was used as an inorganic filler because of its chemical stability (LLZO does not react with Li metal), high ionic conductivity of ~104 S/cm and wide potential window (~5V vs Li/Li+). Therefore, we made a composite membrane by incorporating the ceramic inorganic filler LLZO and improved the ion conductivity such as 4.4 x 10-4 at 55°C of the membrane. However, this membrane still has a low ionic conductivity to be applied to real battery systems because their interface resistance between the electrode and solid electrolyte is large. Mostly, the main internal resistance in ASLBs is the internal resistance between the electrode and the solid electrolyte, not the bulk resistance of the solid electrolyte. In order to enhance further the ionic conductivity of composite membranes, we made hybrid composite membranes by adding small amounts of solvated ionic liquids (SILs). The representative of the SILs is an equimolar mixtures of Li[TFSA] and tetraglyme (abbreviated as [Li1(G4)1][TFSA]), where stable complex cation [Li1(glyme)1]+ is formed and it serves as an analog of the weakly-coordinating cation of the aprotic ILs. [Li1(G4)1][TFSA] showed faster Li+ ion transport than the binary systems of aprotic ILs and Li salts. Also, SILs has low volatility, high ionic conductivities and superior electrochemical stability. Because of these properties, we expected that the ionic conductivity would be increased while maintaining the high thermal and electrochemical stability of the composite membrane. In this study, we propose the novel concept of a free-standing composite membrane with a new family of SILs which has a high ionic conductivity of 1.8 x 10-3 at 55°C. In addition, it had an excellent thermal stability at the temperature. Then we discuss whether the ion conductivity of the composite membrane is improved by adding a small amount of SILs with LLZO based solid electrolyte because of synergetic effects. Finally, the effect of SILs with LLZO based solid electrolyte on the battery performance of the ASLBs cells was investigated.

Study on Li7P3S11 material was carried out by ab initio calculation. using the Vienna ab initio Simulation Package (VASP)[1]. Li7P3S11 was known as a super-ionic conductor (5.4 mS/cm at 25℃) to be a solid-electrolyte of all-solid-state lithium batteries. Two different crystal structure of Li7P3S11 were reported by Onodera (2010) and Tatsumisago (2007) with slight difference on atomic positions. Between total energies of VASP calculation on two structures, Tatsumisago’s structure had slightly more stable energy (Etotal –92.573 eV). Among Li7P3S11, Li3PS4, Li4P2S6 and Li4P2S7, the formation potential of Li7P3S11 was the highest value of 2.216 V(Li/Li+) to be the most stable material. Chemical reactivity of Li7P3S11 material toward moisture to be Li7P3O11 had the reaction energy of –0.34 eV. Li+ conduction of Li7P3S11 take place through vacancy and interstitial diffusion pathways. Xiong (2014) reported on the formation potential of Li7-1P3S11. Here, the formation potential of Li14-xP6S22 (x= 1~14) were evaluated briefly through a stepwise removal of Li+ from Li14P6S22 to Li0P6S22 to be a range of 3.2 ~ 2.6 V. Formation potentials of Li14+1P6S22 were also evaluated for four different interstitial sites. Site(III) denoted at Xiong’s report had 0.643 V(Li/Li+) to be the most easy accommodation of Li+ ion. Patterns of the total density of states (TDOS) of Li14+xP6S22 (x=1,0,-1) were not so different and shown ~3.5 eV by the Hyed-Scuseria-Ernzerhof (HSE) hybrid functional and ~2.1 eV by GGA to be electronic insulator. [1] Kresse,G.; Hafner, J. Phys. Rev. B, 47 (1993) 558; 49 (1994) 14251. Figure 1

Historically, the general strategy for developing new ion-exchange membranes focused almost exclusively on the synthesis of new polymers with a high IEC, where the ion-exchange groups are strongly dissociable. Unfortunately, the use of polymer chemistry alone has not been successful in achieving the performance goals of next-generation proton conducting membranes for fuel cells and redox flow batteries. For example, simply increasing the ion-exchange capacity of a polymer to improve conductivity has lead to polymers that are brittle when dry and swell excessively in water, with a loss in mechanical strength and counterion/coion selectivity. To overcome the problems with highly charged single polymer membrane systems, researchers have: (i) investigated block copolymers which self- assemble into separate phases, where one block provides selective transport pathways and the second block imparts mechanical strength, (ii) combined the desirable properties of two different polymers in a single membrane through blending, (iii) impregnated a functional polymer into a microporous inert support, where the support provides the requisite mechanical properties that the functional polymer lacks, and (iv) crosslinked the ionomer. The present paper will focus on blended ion exchange membranes, composed of perfluorosulfonic acid (PFSA) and polyvinylidene fluoride (PVDF), where nanofiber electrospinning is used to control/alter the nano/micro distribution of PFSA and PVDF. Three membrane fabrication strategies will be presented, using 1100 and 825 EW PFSA and Kynar PVDF: (1) dual fiber electrospinning, where the final membrane morphology is an ionomer matrix with an embedded network of uncharged PVDF reinforcing nanofibers, (2) electrospinning of submicron fibers composed of a PFSA/PVDF polymer blend, followed by fiber mat processing to create a dense and defect-free film, where the morphology is that of randomly oriented bundles of PFSA and PVDF nanofibrils, and (3) core-shell single fiber electrospinning, where the core is PVDF and the shell is a mixture of PFSA and PVDF, followed by compaction and densification to create a dense membrane, where the final membrane structure is similar to that of (1). The methods for fiber electrospinning and follow-on mat processing will be described. Physical property data will be presented for the different fabrication schemes and for different PFSA/PVDF membrane compositions. The use of selected membranes in hydrogen/air and DMFC fuel cells and H2/Br2 redox flow cells will be discussed.

Recently, significant attention has been paid to conventional lithium ion battery (LIBs) with large-scale energy storage and longer cycle properties because new applications, such as electric vehicles (EVs) and energy storage systems (ESSs), are gradually emerging onto the market. Moreover, large-scale battery systems are needed to reduce the system costs of these new applications. Safety issues are of even greater concern for such batteries than for existing smaller batteries. As a promising solution to these issues, the use of a solid electrolyte (SE, based on a polymer and a ceramic) has been suggested [1-2]. In contrast to organic-based liquid electrolytes, all-solid-state lithium ion batteries with a solid electrolyte are considered safe because of their non-flammability. Various solid electrolytes based on high molecular weight dielectric polymer hosts have been tested, and in particular dry electrolyte membranes based on polyethylene oxide (PEO) have been widely studied. PEO-based membranes can be used in all-solid battery designs in a free standing form without modifying current battery fabrication processes[3]. However, the ionic conductivities of PEO-based membranes are very low (10- 6-10- 8 S/cm) at the room temperature because of their low effective carrier mobilities. The carrier mobility can be enhanced by stabilizing the highly conductive amorphous matrix with an inorganic filler (nano-sized SiO2, Al2O3, etc.) [4-5]. However, high ionic conductivities (>10- 4S/cm) can only be obtained in these composites when they have very high filler contents (e.g. >30 wt.%), which result in poor process ability and mechanical properties [6]. In this study, we propose the new concept of a free-standing composite membrane with high ionic conductivity and good process ability, and report our implementation of this concept through the incorporation of garnet-type LLZO solid electrolyte powder into a PEO polymer matrix. Further, we discuss whether the ion conductivity of the composite membrane is improved by adding a small amount of Ionic liquids (ILs) with LLZO solid electrolyte powder because of synergetic effects, and whether the mechanical flexibility of the composite membrane is maintained. Finally, we assess the feasibility of all-solid electrode designs that use oxide solid electrolyte powders. Li7La3Zr2O12 powders were purchased from Nikkiso Co. Ltd. and used as received. The LiClO4/PEO molar ratio was fixed at 1:6, and the amount of LLZO was varied from 37.5 to 47.5 wt.% with respect to the total PEO+LLZO weight of the composite membrane. PEO, LiClO4, and LLZO were simply mixed in acetonitrile (ACN), and the ACN component of the slurry was slowly evaporated at room temperature in a dry-room, resulting in composite solid electrolyte membranes with various LLZO contents in a PEO matrix. Also, optimum condition of the composite membrane with a small amount of ILs was prepared. The ionic conductivity of the electrolytes was determined through complex impedance method using an AC impedance analyzer. The cathode electrode with the optimum composition was prepared as follows. LiNi0.6Co0.2Mn0.2O2/PEO/ LLZO/LiClO4/carbon black (60:15:17.5:2.5:5 wt%) were mixed to create the cathode slurry. A coin cell (2032 type) was fabricated in a dry-room using a composite cathode electrode, solid electrolyte membranes and Li foil anode. The charge-discharge measurements were carried out within 2.5-4.3V. Fig.1a shows the variations of the ionic conductivity of the composite membranes with LLZO content. Increasing the LLZO content from 37.5% to 47.5% enhances the ionic conductivity slightly, but further increases in the LLZO content result in decreases in the ionic conductivity. The composite membrane with the maximum ionic conductivity was prepared under optimum conditions with 42.5% LLZO and 52.5% PEO-LiX. Thus the incorporation of the inorganic phase (LLZO) into the organic matrix (PEO-LiClO4) has a synergetic effect on the Li ionic conductivity. The ionic conductivity of the as-synthesized composite membrane was found to be significantly enhanced with respect to those of PEO-only and LLZO-only membranes, and the optimum composition was determined. Fig.1b shows the variations of the ionic conductivity of the composite membranes with ILs amount. In our approach to enhancing ionic conductivity while retaining a free standing design, we combined the organic matrix (PEO-LiX) and an inorganic solid electrolyte (LLZO) with small amount of ILs to form a composite membrane. The ionic conductivity is increased with adding ILs because the composite membrane of ILs to assist in the formation of ionic contacts. References R. Kanno et al., J. Electrochem. Soc. 148 (2001) A742-A746. A. Hayashi et al., Electrochem. Commun. 5 (2003) 111-114. J. MacCallum, C. Vincent, Polymer Electrolytes Reviews I, Elsevier, London, 1987. B. Scrosati et al., J. Electrochem. Soc. 147 (2000) 1718-1721. L. Persi et al., J. Electrochem. Soc. 149 (2002) A212-A216. X.-W. Zhang et al., J. Power Sources 112 (2002) 209-215. Figure 1

Development of energy storage systems is required to provide stable/continuous electrical energy from intermittent renewable energy sources such as wind and solar. The Hydrogen/Bromine (H2/Br2) regenerative fuel cell is being considered for such applications because of its fast H2 and Br2 electrochemical reaction kinetics and high round-trip efficiency [1]. This type of fuel cell utilizes a membrane-electrode-assembly with a cation-exchange membrane. Although commercial Nafion® is typically used here, its bromine species (Br-, Br2, Br3 -) crossover is high, causing significant columbic losses in the cell and degradation of the platinum catalyst in the hydrogen electrode. The desired cation-exchange membrane would exhibit high proton conductivity, with low bromine species permeability. Electrospinning has been used to fabricate nanofiber composite fuel cell membranes, as an alternative to commercially available films and conventional films from solution-cast polymer blends and copolymers. Pintauro and co-workers demonstrated two different nanofiber electrospinning strategies to fabricate composite fuel cell membranes for hydrogen/air fuel cells: (1) electrospun polyelectrolyte fibers that were impregnated with an uncharged reinforcing polymer matrix [2,3] and (2) dual nanofiber electrospun mats, where the ionomer and uncharged reinforcing polymer are electrospun separately but simultaneously, followed by fiber mat processing to generate one of two distinct membrane morphologies: (i) an interconnected network of ionomer nanofibers embedded in an uncharged polymer reinforcing polymer matrix and (ii) a network of uncharged reinforcing polymer nanofibers surrounded by ionomer. The resultant electrospun composite membranes were shown to have excellent properties for use in a hydrogen/air fuel cell, with improved mechanical properties and lower membrane water swelling than a neat ionomer film, while maintaining a low membrane sheet (areal) resistance [3]. Nanofiber composite membranes from dual fiber mats have also been fabricated and tested for H2/Br2 fuel cells, where the membranes were composed of Nafion and either polyphenylsulfone or poly(vinylidene fluoride) as the uncharged reinforcing polymer [4,5]. For both membrane systems, there was a significant reduction in bromine species crossover, as compared to commercial Nafion®117, with no increase in membrane sheet resistance. Recently, we have developed a new nanofiber electrospinning strategy, where a single solution of a binary polymer mixture consisting of ionomer (i.e., Nafion) and reinforcing polymer, poly(vinylidene fluoride) (PVDF), is electrospun, followed by hot-pressing the resultant nanofiber mat (Figure 1a) into a dense and defect-free membrane. In a further modification of this membrane preparation strategy, we have electrospun Nafion/PVDF blended fibers onto a target drum that is rotating at very high RPM and obtained mats with highly aligned fibers (Figure 1b). To create a membrane, the aligned fiber mats were stacked in multiples layers (with fibers of successive mats rotated 90o) and then hot-pressed, followed by ionomer annealing. Our presentation will focus on the fabrication and characterization of the electrospun Nafion/PVDF membranes from random and aligned nanofiber mats, for use in H2/Br2fuel cells. The membranes will be compared to solution cast Nafion/PVDF blended films and to commercial Nafion 212 in terms of morphology, proton conductivity, swelling, bromine species permeability and mechanical characteristics. References [1] H. Kreutzer, V. Yarlagadda, and T. V. Nguyen, J. Electrochem. Soc., 159, F331, 2012. [2] J. Choi, K. M. Lee, R. Wycisk, P. N. Pintauro and P.T. Mather, Macromolecules, 41, 4569, 2008. [3] J. B. Ballengee and P. N. Pintauro, Macromolecules , 44, 7307, 2011. [4] J. W. Park, R. Wycisk, and P. N. Pintauro, ECS Transactions, 50(2), 1217, 2013. [5] J. W. Park, R. Wycisk, and P. N. Pintauro, “Nafion/PVDF Nanofiber Composite Membranes for Regenerative Hydrogen/Bromine Fuel Cells” J. Memb. Sci. (in press). Figure 1

Fact of Fiction: Do ion-exchange membranes really require complete water saturation in order to possess desirable conductivity? The fabrication of new proton-conducting membranes with a high conductivity at high temperature and low relative humidity conditions is a critically important research challenge for fuel cell developers [1]. Similarly, high conductivity and low crossover membranes are needed in redox flow batteries. Recently, membranes were made by nanofiber electrospinning solutions of perfluoroionomer + PVDF, followed by hot-pressing the resulting blended fiber mat into a dense membrane. These films have unusual and highly desirable properties for use in hydrogen/air fuel cells and/or aqueous flow batteries. In particular, some blended fiber membranes exhibit unusually high proton conductivity at very low water contents. The effect of processing on the complex interplay between the chemical composition, structure and conductivity mechanism of these innovative membranes is still poorly understood. Here we present a complete analysis of the physical-chemical properties as well as the conductivity mechanism of Nafion-PVDF (90wt%/10wt%) membranes obtained from a single fiber mat. These results are contrasted with data collected using a Nafion/PVDF blended membrane prepared by conventional solvent casting. The membranes are extensively characterized by thermoanalytical techniques (water uptake determination, HR-TGA, MDSC, DMA), vibrational spectroscopy (FT-IR ATR) [3], and broadband electric spectroscopy (BES). A Nafion-PVDF (90wt%/10wt%) membrane obtained from an electrospun single fiber mat shows a very low level of water (3 w%) and exhibits high conductivity. The two polymers are found to be well mixed with chains of Nafion surrounding those of PVDF. In addition, there is no evidence of bulk water domains but rather the water molecules are aligned along the polymer chains facilitating a fast proton transfer mechanism. The added benefit of the low water uptake is that there is negligible swelling of the membrane, rendering membranes of this type suitable for a variety of applications. BES measurements are carried out from -100 to 120°C and from 0.03 to 107Hz and are able to elucidate different kind of conductivity mechanisms. The electric response of the Nafion-PVDF (90/10) mat (Figure 1a) and the blend fiber membrane (Figure 1b) are very different from those of Nafion [4], while that obtained from solvent casting (Figure 1c) is similar to Nafion for T>0°C and to mat membrane at T Acknowledgements This research was funded by the Strategic Project of the University of Padua “Materials for Membrane-Electrode Assemblies to Electric Energy Conversion and Storage Device (MAESTRA)” and by Veneto Nanotech S.C.p.a. (Venice). REFERENCES [1] V. Di Noto, T.A. Zawodzinski, A.M. Herring, G.A. Giffin, E. Negro, S. Lavina, Int. J. Hydrogen Energy 37, 6120 (2012). [2] J.B. Ballengee, P.N. Pintauro, J. Membr. Sci. 442, 187 (2013). [3]. E. Negro, M. Vittadello, K. Vezzù, S. J. Paddison, V. Di Noto, Solid State Ionics 252, 84 (2013). [4] V. Di Noto, M. Piga, G. Pace, E. Negro, S. Lavina, ECS Trans. 16, 1183 (2008). Figure 1

Recently, a substantial improvement in the energy density has been achieved through an asymmetric electrode design of utilizing a lithium-ion intercalating electrode as the negative electrode, instead of one of the activated carbon (AC) electrodes in a commercial electric double layer capacitor (EDLC) ; so-called hybrid capacitor such as lithium-ion capacitor (LIC) or nano hybrid capacitor1-7). In these hybrid capacitor, during charge/discharge, lithium-ion intercalation/de-intercalation occurs within the bulk of the negative electrode, whereas, anion adsorption/desorption occurs on the surface of the AC positive electrode. Negative electrodes, in generally, are typically produced with increased density in order to minimize contact resistance of carbons and obtain the higher volumetric capacity in the electrode. However, C-rate of graphite according to literatures shows rapid reduction in C-rate after approximately 2C8). In this study, we have investigated the manufacturing parameters to enhance the rate-capability of negative carbon-electrode by controlling the electrode density. Natural graphite as a negative electrode material was commercially supplied by Aldrich Chemical Co. The negative electrodes were prepared by coating the mixture of natural graphite with particle size of 20μm, a carbon additive (Super P), and poly(vinylidene difluoride) (PVdF) as a binder by 96 : 1 : 3 mass ratio on a Cu foil. The negative electrodes with different electrode density were prepared by controlling the loading density. Unit cells composed by having Li foil for positive electrode and natural graphite electrode for negative electrode, and 1M LiPF6 in EC/DEC/EMC was used as an electrolyte. In this study, the electrode densities were controlled in the range of 0.7 to 1.5 g/ml. It was observed, in the C-rate capabilities, that Rapid reduction in C-rate after approximately 2C was observed for natural electrode with 1.5 g/ml, which is similar behavior as shown in results of literature8). However, it can be seen that there is rapid improvement in C-rate when the electrode density is varied. As the electrode density decreases from high density to low density, the enhanced C-rate performances were observed. In this result, it can be noted that 50% of relative discharge ultimate at 30C was obtained for the graphite electrode with 0.7 g/ml. High power performances in graphite electrode with lower electrode density can be discussed as follows. Electrode with high density presumably has wide contact surface between the carbons with narrow space in between the carbon particles, which would cause unsmooth supply of electrolytes. Consequently, this would cause relatively increased diffusion resistance since electrolytes need to be brought from area included in the separator that is present between the electrodes. However, there are many open voids in the electrode with lower density. These open voids acts as electrolyte reservoir, and ionic mobility would be fast between open voids and carbons. Therefore, these fast rocking chair behavior of ions causes to decrease the diffusion resistance. References [1] S. R. Sivakkumar, A. G. Pandolfo, Electrochem. Acta, 65 (2012) 280. [2] G. G. Amatucci, F. Badway, A. D. Pasquier, T. Zheng, J. Electrochem. Soc. , 148 (2001) A930. [3] A. Du Pasquier, I. Plitz, S. Menocal, and G. Amatucci, J, Power Sources, 115 (2003) 171. [4] A. Du Pasquier, I. Plitz, J. Gural, S. Menocal, G. Amatucci, J. Power Sources, 113 (2003) 62. [5] I. Plitz, A. Du Pasquier, F. Badway, J. Gural, N. Pereira, A. Gmitter, G. G. Amatucci, Appl. Phys, A: Mater.Sci. Process., 82 (2006)615. [6] K. Naoi, P. Simon, Electrochem. Soc. Interface, 17 (2008) 34. [7] A. Yoshino, Y. Tsubata, M. Shimoyamada, H. Satake, Y. Okano, S. Mori, S. Yata, J. Electrochem. Soc., 151 (2004) A2180. [8] S. R. Sirakkumar, J. Y. Nerkar, A. G. Pandolfo. Electrochemica Acta., 55 (2010) 3330-3335.

In 2008, Pintauro and co-workers [1] showed how nanofiber electrospinning can be used to fabricate composite fuel cell membranes. The method of membrane fabrication and the membrane morphology were alternatives to traditional membranes based on polymer blends and copolymers. These early membranes were made by electrospinning an ionomer fiber mat followed by the impregnation of an uncharged, reinforcing polymer into the inter-fiber voids.A series ofpost-electrospinning processing steps were required to convert a porous mat into a dense and defect-free fuel cell membrane, namely (a) mat compression, (b) fiber welding, (c) ionomer annealing, and (d) inert polymer impregnation. The resultant nanofiber composite membrane morphology decoupled the proton conduction function of the ionomeric nanofibers from the mechanical support and swelling control functions of the uncharged matrix polymer. Dual-fiber electrospinning was introduced in 2011 by Ballengee and Pintauro [2] as a means to eliminate a separate interfiber void-filling impregnation step during nanofiber composite membrane fabrication. Here, the ionomer and uncharged polymers were simultaneously electrospun as separate fibers that co-deposited as a well-mixed mat on the rotating drum collector surface. Subsequent processing via hotpressing and either annealing or solvent vapor exposure, induced the flow of one of the polymer components into the interfiber void space while retaining the nanofiber morphology of the second polymer. Two membrane morphologies were produced from a single dual fiber mat: (i) an interconnected network of ionomer nanofibers embedded in an uncharged polymer reinforcing polymer matrix and (b) a network of uncharged reinforcing polymer nanofibers surrounded by an ionomer matrix. In the dual fiber membrane work, the ionomer was NafionÒ perfluorosulfonic acid polymer and the uncharged polymer was polyphenylsulfone. Recently our group has begun fabricating dual-fiber Nafion-PVDF and AquivionÒ-PVDF composite proton conducting membranes (Aquivion is a short side chain 825 EW PFSA polymer from Solvay Solexis). These membranes were designed for use in regenerative hydrogen-bromide and conventional hydrogen/air fuel cells. Two general membrane structures were prepared: (1) membranes with “melted” PVDF fibers that fill the voids between PFSA fibers, and (2) membranes with “melted” PFSA which fills the voids between PVDF nanofibers. These two membrane types were obtained from the same as-spun two-component mats using the procedures described in the preceding paragraph. The PFSA content of membranes was typically in the range 30-60% PVDF for morphology #1 and 20-50% for morphology #2. This presentation will provide additional details regarding the fabrication and properties of PFSA/PVDF fuel cell membranes. Specific topics to be covered in the talk are: New ways of electrospinning Nafion and Aquivion nanofibers Nanofiber composite membranes where an interconnecting network of PFSA nanofibers is embedded in a PVDF matrix. Nanofiber composite membranes where PVDF nanofibers are embedded in a PFSA matrix PFSA/PVDF blended membranes with no nanofiber morphology. The various membranes in items 2-4 will be contrasted with one another and with commercial Nafion 212 films in terms of the following fuel cell properties: proton conductivity, gravimetric and areal water swelling, wet/dry mechanical properties, and gas permeability. Physical property differences will be linked with changes in membrane morphology. References [1] J. Choi, K.M. Lee, R. Wycisk, P.N. Pintauro and P.T. Mather, Macromolecules, 41, 4569, 2008. [2] J.B. Ballengee and P.N. Pintauro, Macromolecules , 44, 7307, 2011.

Supercapacitors are of practical interest owing to their high power electrical energy storage and exceptionally long cycle life. Also, it has been used and developed such as memory back up for electric home appliance and information transport devices, renewable energy and power assist for transportation and machinery, voltage sag and renewable energy sources for stable electric power. Significantly, electric double layer capacitor (EDLC) consist of stacked activated carbon shows superior high power characteristics whereas it has low energy density as a drawback. Therefore, hybrid capacitor is one of possible candidates and is developing for high energy density. The hybrid capacitor is made up with activated carbon electrode for electric double layer capacity and anode for intercalation and de-intercalation of lithium ions. Although it shows inevitable increase of energy density [1-3], the total output power is lower than that the EDLC due to chemical reaction on the anode. To increase the power density, the decrease of intercalation length for low diffusion resistance is necessary. The hybridization of activated materials with carbon nanotubes, carbon nanofiber, and graphene is intriguing for the application of highly conductive cathode electrode. Here, we introduce the preparation of carbon electrodes to enhance the output power on the anode without high-dimensional and high cost method. In general, high density electrode has high power characteristics because of low contact resistance. However, in this study, the decrease of electrode density can be increase dramatically the output power in the high current density. This result may give rise to the decrease of diffusion resistance due to the low electrode density and the stable surface electrolyte interface at the reacting surfaces.

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In this study, we investigated the structural and optical properties of Ge-doped SbTe Ge–ST thin films with three differing compositions: Ge0.06Sb0.77Te0.17 Ge–STH ,G e 0.05Sb0.70Te0.25 Ge–STM, and Ge0.05Sb0.64Te0.31 Ge–STL, grown on Si substrate by radio-frequency sputtering method. The films were annealed at 250°C for crystallization and their crystal structures were examined by X-ray diffraction. Compared to the X-ray diffraction spectra of the undoped SbTe, the Ge–ST thin films had a hexagonal structure with large stacking periods. Using Raman spectroscopy, we investigated the shift of the phonon mode frequencies A1g and Eg of the films with varying Sb:Te ratios. We compared the dependence of the phonon frequencies of Ge–ST on the Sb content to those of the corresponding undoped SbTe. The composition dependence of the A1g phonon frequency could be explained in terms of the linear extrapolation of Sb and Sb2Te3 crystals. By using spectroscopic ellipsometry, we measured the dielectric function of the thin films in the near-IR, visible, and ultraviolet spectral regions. The optical energy gaps and bandgaps of the amorphous and crystalline phases, respectively, were determined using linear extrapolation of the absorption coefficient. The optical gap energies of the amorphous Ge–ST films were determined to be about 0.5–0.6 eV, whereas the indirect bandgap energies of the crystalline films shrank substantially to about 0.15–0.2 eV.

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