Chemistry Letters Research Articles

Crystal and Local Structure Analyses for Layered Rock-Salt Type LixMn0.9Ti0.1O2 Prepared By Soft Chemical Synthesis

Introduction There has been considerable interest in the layered rock-salt type oxides for the positive electrode materials in secondary lithium ion batteries (LIBs). The lithium cobalt oxide, LiCoO2, has been attracted much attenstion for many years because of its high electric capacity and excellent cycle life. The high cost and toxicity of cobalt compounds, however, have led to the investigation of alternative materials. So far, the layered rock-salt type LiNiO2, LiNi0.5Mn0.5O2, LiMnO2 and Li2MnO3-LiMO2 compounds (M = Mn, Co, Ni) have been intensively studied. Although Li2MnO3-LiMO2 materials showed high capacity, the the initial charge/discharge process was characterized by low coulombic efficiency. On the other hand, the disadvantage of meta-stable LiMnO2 was to convert to spinel-type structure on charge-discharge cycling. The phase transformation was suppressed by the partial substitution of the titanium ion for manganese ion [1]. Thus, expectation in regard to the modified Mn-rich layered oxide, LiMn0.9Ti0.1O2, is fairly high on the capacity and cycle life. The soft chemical synthesis has opened route for the synthesis of layered rock-salt type LiMn0.9Ti0.1O2 that are difficult or impossible to obtain by high temperature solid-state reactions. The advantage of such a soft chemical method is to induce the preparation of meta-stable phases and to considerably reduce the formation temperature below 500 ºC. In order to alleviate reaction conditions, environmental impact and decrease the economic cost, the synthesis of this material through soft chemical method would be prior if the properties of the material could be retained. In this study, the LixMn0.9Ti0.1O2 was examined about the crystal and local structures. Experimental We have attempted the preparation of LixMn0.9Ti0.1O2 with the O3-type layered structure by Na+/Li+ ion exchange using the corresponding sodium compounds as starting materials. The precursors of Na0.7Mn0.9Ti0.1O2 was prepared by solid-state reaction of stoichiometric mixtures of CH3COONa (purity 98.5%, Wako Pure Chem.) and coprecipitated manganese-titanium hydroxides. The powders were mixed by grinding and heated in a box furnace at 500 °C for approximately 12h in air. The (Li,Na)xMn0.9Ti0.1O2 sample was prepared by Na+/Li+ ion exchange of Na precursor with an eight fold molar excess of LiBr (purity > 99%, Strem Chem.) for 6 h in ethanol at 80 °C. After ion exchange, the samples were washed in ethanol and water. Chemical analyses for Li, Na, Mn, and Ti were carried out by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Powder X-ray diffraction data were collected on a Panalytical X’pert-pro diffractometer. The morphology was observed by scanning electron microscopy (SEM, Hitachi, S-2600N). The crystal structure analysis was performed by using the synchrotron X-ray diffraction at BL02B2 (SPring-8, JAPAN). The local structure was examined by the X-ray total scattering at BL04B2 and the XAFS at BL14B2 (SPring-8, JAPAN). Charge and discharge tests were performed at 25 °C using a positive electrode, which consisted of the sample, conductvie carbon, and poly-tetrafluoroethylene powder between 2.5 and 4.8 V using a Li-metal negative electrode at a fixed current density of 30 mA g-1. A solution of 1 M LiPF6 in a 1:2 mixture of EC/DMC by volume (Kishida Chemical Co., Ltd.) was used as the electrolyte. The cells were constructed in an argon-filled globe box. Results and Discussion The XRD pattern for the precursor, Na0.7Mn0.9Ti0.1O2, was not attributed to any phases as previously shown [1]. The Na+/Li+ ion exchange for Na0.7Mn0.9Ti0.1O2 resulted in the chemical composition of the Li0.6Na0.1Mn0.9Ti0.1O2. After the ion exchange, the XRD pattern mainly showed the O3-type structure with a few unknown weak diffractions. The SEM observation revealed the grain size of about 200 nm. The electrochemical property of ion-exchanged material showed 243 mAh g−1 at first discharge. The synchrotron X-ray diffraction pattern of ion-exchanged material was analysed by Rietveld method and was not fully fitted to layered rock-salt structure with R-3m. Therefore the EXAFS and X-ray total scattering (Fig.) were also examined to analyse the local structure of Li0.6Na0.1Mn0.9Ti0.1O2. The reduced pare distribution function indicated that the structure of Li0.6Na0.1Mn0.9Ti0.1O2 was locally characterized as the spinel type and/or hollandite type structure. Reference [1] N. Ishida, H. Hayakawa, H. Shibuya, J. Imaizumi and J. Akimoto, Chemistry Letters, 10, 1478 (2012) Figure 1

Investigation of a Correlation Between Structures of Mesoporous Carbon an Gas Adsorption Characteristics

Introduction PEFCs are paid much more attention since the commercialization of FCVs and are deeply related to carbon materials, which are components of PEFCs themselves and also related systems. In our group, we have been studying mesoporous carbon (MC), which has meso-channel structures with about 10 nm diameter, as a catalyst support and have successfully improved durability of PEFCs, so far. In order to further improve performance and durability of PEFCs and related systems, it is important to understand the fundamentals of adsorption properties of fuels involving hydrogen gas, oxygen gas, and water vapor. In this research, a correlation between structures of mesoporous carbon and gas adsorption characteristics is investigated. Experimental General MC was synthesized by mixing Pluronic® F127, resorcinol, formaldehyde, and trimethyl orthacetate and heated under nitrogen atmosphere. Other MC materials1 were also made by slightly different conditions as shown in Table 1. Then, gas adsorption properties of each sample were evaluated after the ball milling and heat treating at 900 oC. Results & discussion Hydrogen adsorption dependence on the pore size of MC is discussed here. If MC#1 and MC#2 in Table 1are compared, MC#2 has larger pores based on the pore distribution obtained from nitrogen adsorption measurements. The values of BET specific surface area of the MC#1 and the MC#2 results in not very much different, 615 m2/g and 650 m2/g, respectively. The maximum hydrogen absorption content (wt%) at 7 MPa has resulted in 0.6 % for MC#1 and 0.35 % for MC#2. Considering Chahine rule2 for carbon materials, revealing that linear relationship between the hydrogen absorption content and the specific surface area, our results are against that rule. Therefore, hydrogen adsorption properties can be explained by other than the specific surface area in our materials. The possible mechanism of hydrogen adsorption is further discussed through the analyses of several MC materials. (1) Y. Sonoda, A. Hayashi, Y. Minamida, E. Akiba, Chemistry Letters, 44, 503-505 (2015). (2) R. Chahine, T.K. Bose, 11th WHEC, 1996; Pergamon Press: Oxford, U.K., 1259 (1996). Figure 1

The Role of Temperature on Salt Removal Using Capacitive Deionization

Current technologies utilized for seawater desalination, reverse osmosis (RO) and Membrane distillation (MD), are energy intensive because they operated by separating the main component water (H2O) from the salt (NaCl). Capacitive deionization (CDI), an emerging separations based technology, operates by extracting the minority component (NaCl). CDI is similar to a supercapacitors[1], where ions adsorb to the high surface area activated carbon once an electric potential is applied across the electrochemical cell (ion separation process)[2-5]. However, in place of traditional non-aqueous based electrolytes is a electrolyte comprised of sea, brackish or wastewater. More recent theoretical based studies have emphasized the role heat transfer has on ion adsorption dynamics within CDI cells[6].Traditional CDI cells operate in a cyclic process where the capacitive electrodes are brought in contact with a concentrated salt solution (e.g. brackish water) and charged. Once the charged electrodes are fully saturated with salt ions, the electrodes are regenerated through discharging the electrodes in a brine solution. Analogous to a P-V diagram for traditional heat engines, the enclosed area of the charge versus voltage represents the energy consumed during this charging-discharging process. Here we explore the effect of temperature on salt removal in a CDI cycle. Experimentally, we use traditional electrochemical characterization methods, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), to evaluate the capacitance and resistance changes with temperature. Specifically the salt adsorption capacity is shown to decrease from 13.82±1.13, to 6.58±1.01 milligram NaCl/mg carbon as the cell temperature is increased from 25oC to 45oC. 1. Hatzell, K.B., M. Boota, and Y. Gogotsi. Chemical Society Reviews, 2015. 44(23): p. 8664-8687. 2. Porada, S., R. Zhao, A. Van Der Wal, V. Presser, and P. Biesheuvel.Progress in Materials Science, 2013. 3. Hatzell, K.B., M.C. Hatzell, K.M. Cook, M. Boota, G.M. Housel, A. McBride, E.C. Kumbur, and Y. Gogotsi. Environmental science & technology, 2015. 49(5): p. 3040-3047. 4. Ren, C.E., K.B. Hatzell, M. Alhabeb, Z. Ling, K.A. Mahmoud, and Y. Gogotsi. The journal of physical chemistry letters, 2015. 6(20): p. 4026-4031. 5. Hatzell, K.B., E. Iwama, A. Ferris, B. Daffos, K. Urita, T. Tzedakis, F. Chauvet, P.-L. Taberna, Y. Gogotsi, and P. Simon. Electrochemistry Communications, 2014. 43: p. 18-21. 6. Janssen, M., A. Härtel, and R. Van Roij. Physical review letters, 2014. 113(26): p. 268501.

Indirect and Direct Observation of Ionomer Colloidal Systems with Applications to Fuel-Cell Catalyst Layers

Manufacturing methods for fuel cell catalyst layers are critically important for achieving high material utilization and performance. Typically, electrode systems are cast from an ‘ink’ or ‘colloidal’ state, where the solid material is suspended in a solution containing a solvent and a polymer. For polymer-electrolyte fuel cells, a perfluorinated sulfonic-acid (PFSA) ionomer, typically Nafion, is used in the ink and catalyst layer, where its roles are to act as a binding agent and conduit for proton conduction to the reaction site.1 Recently, it has been suggested that the ionomer film that surrounds the platinum reaction site may contribute to increased resistances that limit performance at low Pt loadings.1,2 Thus, it is of great interest to understand the factors controlling the film formation in catalyst layers to optimize material properties and cell performance. The nature of the dispersion and casting process could have significant influence on the morphology and properties of the dispersion-cast membranes.3-5 To isolate these effects, the morphology of PFSA dispersed in various solvents (glycerol, water/2-propanol, and NMP) was reported previously using small angle neutron scattering (SANS), where catalyst layers from the different solvents exhibit different performance.6 The understanding of local‘ink’ structures as a function of active material (polymer and solid) volume fraction (Φ) and across solvent space and length scales can aid in understanding bulk properties and the impact of ink formulation in cast systems. In this talk, a direct observation of the colloidal suspension of the ionomer in different solvents will be described using confocal laser scanning microscopy (CLSM). CLSM has long been utilized as a tool for characterizing the structure of biphasic colloidal gels. We combine dynamic light scattering, ultra-small angle x-ray scattering, and confocal microscopy to understand PFSA size and structure in dilute (1,3, and 5 wt%) ionomer solutions. The structural formation of nafion membranes are observed in-situ with small angle x-ray scattering. Finally, we contrive a model ‘ink’ composed of attractive and repulsive silica spheres and PFSA suspended in different solvents (water, NMP, and isopropyl-alcohol) and use CLSM to gain a greater understanding about solid|PFSA interactions in model inks. 1. A. Z. Weber and A. Kusoglu, Journal of Materials Chemistry A, 2, 17207 (2014). 2. A. Kongkanand and M. F. Mathias, The Journal of Physical Chemistry Letters, 1127 (2016). 3. T. T. Ngo, T. L. Yu and H.-L. Lin, Journal of Power Sources, 225, 293 (2013). 4. C.-H. Ma, T. L. Yu, H.-L. Lin, Y.-T. Huang, Y.-L. Chen, U. S. Jeng, Y.-H. Lai and Y.-S. Sun, Polymer, 50, 1764 (2009). 5. Y. S. Kim, C. F. Welch, R. P. Hjelm, N. H. Mack, A. Labouriau and E. B. Orler, Macromolecules, 48, 2161 (2015). 6. C. Welch, A. Labouriau, R. Hjelm, B. Orler, C. Johnston and Y. S. Kim, Acs Macro Letters, 1, 1403 (2012).

Promoting Solution Phase Discharge in Li-O2 Batteries

Li-ion and related battery technologies will be important for years to come. However, society needs energy storage that exceeds the capacity of Li-ion batteries. We must explore alternatives to Li-ion if we are to have any hope of meeting the long-term needs for energy storage. One such alternative is the Li-air (O2) battery, Fig. 1; its theoretical specific energy exceeds that of Li-ion, but many hurdles face its realization.[1-5] One spin-off of the recent interest in rechargeable Li-O2 batteries, based on aprotic electrolytes is that it has highlighted the importance of understanding the fundamental processes at the positive electrode within the battery.[6- 12 ] Based on these studies, it is generally accepted that a solution growth mechanism will be required to achieve high rates and capacities. One way to achieve discharge in solution is use of high donor or acceptor number (DN/AN) electrolytes, which might be less stable towards LiO2 and Li2O2 than their low DN/AN counterparts. To solve this dilemma, a reduction mediator was introduced into the low DN/AN electrolyte to encourage the discharge in solution. By forming an intermediate complex, it suppresses the direction reduction to Li2O2 on surface and thus leads to higher capacity on discharge with higher rates. Furthermore, if Li2O2 is formed in solution a charge mediator will be required, as the traditional electrode configuration is unable to oxidize the product. The implication of this is complete solution phase cycling where solid Li2O2is simply a storage material for lithium ions and electrons. REFERENCES [1]. Bruce, P. G.; Freunberger, S. A.; Hardwick, L. J.; Tarascon, J.-M. Nature Materials 2012, 11, 19. [2]. Lu, Y. C.; Gallant, B. M.; Kwabi, D. G.; Harding, J. R.; Mitchell, R. R.; Whittingham, M. S.; Shao-Horn, Y. Energy & Environmental Science 2013, 6, 750. [3]. Black, R.; Adams, B.; Nazar, L. F. Advanced Energy Materials 2012, 2, 801. [4]. Girishkumar, G.; McCloskey, B.; Luntz, A. C.; Swanson, S.; Wilcke, W. The Journal of Physical Chemistry Letters 2010, 1, 2193. [5]. Li, F.; Zhang, T.; Zhou, H. Energy & Environmental Science 2013, 6, 1125. [6]. Horstmann, B.; Gallant, B.; Mitchell, R.; Bessler, W. G.; Shao-Horn, Y.; Bazant, M. Z. The Journal of Physical Chemistry Letters 2013, 4, 4217. [7]. Hummelshoj, J. S.; Luntz, A. C.; Norskov, J. K. The Journal of Chemical Physics 2013, 138, 034703. [8]. McCloskey, B. D.; Scheffler, R.; Speidel, A.; Girishkumar, G.; Luntz, A. C. The Journal of Physical Chemistry C 2012, 116, 23897. [9]. Trahan, M. J.; Mukerjee, S.; Plichta, E. J.; Hendrickson, M. A.; Abraham, K. M. Journal of The Electrochemical Society 2013, 160, A259. [10]. Sharon, D.; Etacheri, V.; Garsuch, A.; Afri, M.; Frimer, A. A.; Aurbach, D. The Journal of Physical Chemistry Letters 2012, 4, 127. [11]. Jung, H. G.; Kim, H. S.; Park, J. B.; Oh, I. H.; Hassoun, J.; Yoon, C. S.; Scrosati, B.; Sun, Y. K. Nano Letters 2012, 12, 4333. [12]. Zhai, D.; Wang, H. H.; Yang, J.; Lau, K. C.; Li, K.; Amine, K.; Curtiss, L. A. Journal of the American Chemical Society 2013, 135, 15364.

Investigation of the Performance of PtCo/C Cathode Catalyst Layers for ORR Activity and Rated Power for Automotive Pemfcs

In order to simultaneously meet the automotive PEMFC targets of cost, performance and durability, Pt-alloys electrocatalysts are being intensively investigated.1,2,3 Pt-alloys show promise of higher ORR mass activities that will permit the use of lower Pt loadings (~0.1 mgPt/cm2) in the cathode catalyst layers. In this work we have studied several Pt-Co/C catalysts that exhibit mass activities that exceed the DOE target of 440 mA/mgPt at 0.90V, 80oC, 100% RH for ORR activity. The performance at rated power density of 1W/cm2 at 0.60V is more difficult to achieve at low loadings due to unanticipated transport resistances. In addition to carrying out ORR activity studies both in TF-RDE set-ups4,5 as well as in MEAs of subscale cells, we have also applied complementary diagnostics of wet and dry H2-Air curves, microscopy of catalyst powders and catalyst layer films, EIS and dilute oxygen limiting current studies6 on these materials. Rigorous base-lining was carried out to obtain the ORR activity of a commercial Pt/C catalyst in order to benchmark the Pt-Co/C catalysts under study using identical protocols.7,8 Although we easily achieve the mass activity targets at 0.90V, we only approach the rated power targets indicating that further understanding of the transport resistances at high current densities and low Pt loadings is necessary to identify and mitigate the losses. Acknowledgements: This work was funded through the DOE FC-PAD Consortium. References Mathias MF, Makharia R, Gasteiger HA, Conley JJ, Fuller TJ, Gittleman CJ, Kocha SS, Miller DP, Mittelsteadt CK, Xie T, Van SG. Two fuel cell cars in every garage. Electrochem. Soc. Interface. 2005;14(3):24-35. Gasteiger HA, Kocha SS, Sompalli B, Wagner FT. Activity benchmarks and requirements for Pt, Pt-alloy, and non-Pt oxygen reduction catalysts for PEMFCs. Applied Catalysis B: Environmental. 2005 Mar 10;56(1):9-35.Kongkanand A, Mathias MF. The Priority and Challenge of High-Power Performance of Low-Platinum Proton-Exchange Membrane Fuel Cells. The journal of physical chemistry letters. 2016 Mar 11;7:1127-37.Kocha SS, Zack JW, Alia SM, Neyerlin KC, Pivovar BS. Influence of ink composition on the electrochemical properties of Pt/C electrocatalysts. ECS Transactions. 2013 Mar 15;50(2):1475-85.Shinozaki K, Zack JW, Pylypenko S, Pivovar BS, Kocha SS. Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique II.Baker DR, Caulk DA, Neyerlin KC, Murphy MW. Measurement of oxygen transport resistance in PEM fuel cells by limiting current methods. Journal of The Electrochemical Society. 2009 Sep 1;156(9):B991-1003.Kocha SS. Principles of MEA Preparation in Handbook of Fuel Cells: Fundamentals, Technology, and Applications; Vol. 3, edited by W. Vielstich, A. Lamm, and HA Gasteiger. Ch.;43:538.Neyerlin KC, Gu W, Jorne J, Clark A, Gasteiger HA. Cathode catalyst utilization for the ORR in a PEMFC analytical model and experimental validation. Journal of The Electrochemical Society. 2007 Feb 1;154(2):B279-87.

Influence of Alloying on CO2 Electroreduction on Ag-Zn System

Electrochemical reduction of CO2 is an attractive pathway for the sustainable production of fuels and chemicals, as it allows for the effective use of renewable energy sources while mitigating the effects of CO2 in the atmosphere. While significant decrease in overpotentials and increase in reaction rates have been reported for the two-electron reduction products, reports on improved activity and selectivity for the products that require more than two electrons (> 2 e- products) have been limited on monometallic transition metal catalysts. Recent theoretical work indicates that this difficulty of reducing CO2 to > 2 e- products is due to the linear scaling of the binding energies of CO2 reduction intermediates on transition metal catalysts, and the necessity of catalyst systems that can break such scaling has been emphasized.(1) Alloys, which can provide bifunctional sites that selectively stabilize intermediates, are a promising class of materials, and a large amount of effort has been focused on the investigation of their effectiveness as CO2 reduction catalysts. Recent works have reported on improved CO2 reduction activity and selectivity on alloy systems, which were attributed to the synergy between the two metal atoms at the surface. However, most improvements reported in these works are pertaining to two-electron products, and alloy systems that demonstrate improvements for > 2 e- products remain elusive. Here, we report on the investigation of polycrystalline AgZn foil, which resulted in the observation of enhanced activities and selectivities for methane and methanol productions compared to Ag and Zn foils. Although CO is the main CO2 reduction product as expected of an alloy between two metals active for CO production, the selective enhancement observed for the > 2 e- products is noteworthy, as it indicates that alloys are promising candidates in the development of effective CO2 electroreduction catalysts. The production of CO as major product is explained by the binding energies of intermediates, and the importance of optimal binding energies are discussed. Reference 1. A. A. Peterson and J. K. Nørskov, The Journal of Physical Chemistry Letters, 3, 251 (2012).

Models to Couple Mechanics and Electrochemical Transport in Solid Electrolytes

Electrolytic transport models available in the literature primarily deal with liquid media; models for solid electrolytes in polymer-electrolyte-membrane (PEM) fuel cells [1] largely derive from theories originally formulated to describe fluids. Since a solid can sustain a deformation at equilibrium under an applied stress or strain, there is a fundamental difference in the transport physics. Accurately modelling water-induced swelling in ionomer membranes requires that solid mechanics be reconciled with the transport and kinetic behaviour of electrochemical systems [2]. Previous efforts made to consider membrane swelling usually operate on a global basis, accounting only for an overall volume change; it is not clear whether models that include local swelling effects do so in thermodynamically consistent ways. This talk will deal specifically with swollen ionomers, although the principles introduced apply equally well to other solid ion conductors. In the case of Nafion, as Fig. 1 shows, water and ionic transport can produce, and dynamically interact with, non-uniform local volume changes and associated distributions of stress, making electrochemical/mechanical coupling significant. Our strategy is to return to first principles, identifying and undoing the assumptions made specifically for liquid mixtures, and finding ways to ensure that the simultaneous use of ostensibly independent theories of kinematics, thermodynamics, and transport does not induce internal inconsistencies in the model. The incorporation of additional state variables such as pressure, stress, and strain requires the inclusion of new balance equations and constitutive laws: one must carry along a local balance of momentum, which relates the local pressure within the electrolyte to the distributions of stress and inertia; there must be a stress constitutive law that characterises the mechanical response (viscous, elastic, viscoelastic etc.); and strain must be defined in such a way that it ties deformed coordinates to a reference state while simultaneously abiding by the thermodynamic volume-explicit equation of state. Modifying the system of equations in the manner discussed above and tackling questions of model closure have helped us to produce a more robust and comprehensive set of equations to model Nafion. The underlying aim is to combine developments in continuum poroelasticity theory with advanced electrochemical transport models. Ultimately, such a model will help us rationalise the physics associated with swollen vapour-equilibrated Nafion-like membranes in fuel cells under isothermal, non-isobaric, and constrained or free-swelling conditions. Such a model could inform better water management schemes and efforts to improve membrane durability. It will also be useful to have a general framework for modelling solid electrolytes that can be applied to materials beyond Nafion where electrochemical/mechanical coupling is important. [1] Weber, A.Z. and J. Newman, Transport in polymer-electrolyte membranes - II. Mathematical model. Journal of the Electrochemical Society, 2004. 151(2): p. A311-A325. [2] Kusoglu, A. and A.Z. Weber, Electrochemical/Mechanical Coupling in Ion-Conducting Soft Matter. The Journal of Physical Chemistry Letters, 2015. 6(22): p. 4547-4552. Figure 1

X-Ray Absorption Spectroscopic Analysis of Li3PS4 Glass-Carbon Composite Cathodes for All-Solid-State Lithium Secondary Battery

All-solid-state lithium secondary batteries with sulfide inorganic solid electrolytes have attracted attention because of their outstanding safety performance. However, the practical capacity of cathodes for all-solid-state batteries is smaller than lithium-ion battery cathodes because the composite electrodes are contained by solid electrolyte powder. To increase the practical capacity of composite cathodes, the composite material of milling Li3PS4 solid electrolyte with acetylene black was examined as an active material.1 While the improved capacity of cathodes was reported, the reaction mechanism of this active material has not been clarified yet. In this study, we investigated the electronic structure change of Li3PS4-acetylene black composite electrodes during charge-discharge for sulfide all-solid-state lithium secondary battery. The 75Li2S-25P2S5 (mol %) glass used as solid electrolyte for all-solid-state cells was prepared by mechanical milling. The Li3PS4-acetylene black composite electrode was obtained by ball milling of the mixture of the Li3PS4 and acetylene black with the weight ratio of 70:30 at 370 rpm for 1 h. All-solid-state battery cells were fabricated as follows. The Li3PS4-AB composite electrode (5–6 mg) and the 75Li2S-25P2S5 glass (80 mg) were set in a polycarbonate tube (φ10 mm) and pressed together under 360 MPa. An indium foil with a thickness of 100 μm was then placed on the surface of the solid electrolyte side of the bilayer pellet as a counter-reference electrode. Electrochemical tests of the cells were conducted at a constant current density of 0.064 mA cm−2 at 25 °C in an Ar atmosphere. X-ray absorption spectroscopy (XAS) was carried out at the beamline BL-13 in the SR center, Ritsumeikan University. Charged or discharged Li3PS4-AB composite electrodes were transferred into the chamber for XAS measurements. XRD patterns of charged and discharged sample showed no new peaks and Raman spectra showed remained PS4 3- anions in charge-discharge process. XPS analysis showed that new S-S covalent bonds were detected after charge. From S K-edge XAS spectra, the peak top was shifted from 2471 eV to 2472 eV and the intensity of the peak increased during charging. The change of S K-edge XAS clearly indicates the electronic structure of sulfur largely contribute the redox reaction in Li3PS4-AB composite electrode. Moreover, the extended X-ray absorption fine structure analysis showed the formation of S-S bonds in the charge reaction. 2 Reference 1. Hakari, T., Nagao, M., Hayashi, A., and Tatsumisago, M.,J. Power Sources, 2015, 293, 721-725. 2. Cuisinier, M., Cabelguen, P.-E., Evers, S., He, G., Kolbeck, M., Garsuch, A., Bolin, T., Balasubramanian, M., and Nazar, L. F.,The Journal of Physical Chemistry Letters, 2013, 4(19), 3227-3232. Acknowledgement This research was financially supported by Advanced Low Carbon Technology Research and Development Program (ALCA).

Modelling the Electrochemical Interface: Applications to CO2 Reduction

The electroreduction of CO2 has the potential to store energy from intermittent renewable sources and to produce carbon-neutral fuels and chemicals [1, 2]. In recent years, theoretical studies of CO2 reduction have usually applied the computational hydrogen electrode model, which allows for the determination of the energies of reaction intermediates without explicitly treating the potential and the ions in solution [3]. In this talk, I will briefly review the application of this approach to CO2 reduction: the determination of lowest free energy pathways and correlation of theoretical activity volcanoes with experimental onset potentials [4, 5], and the computational screening of new catalysts [6]. I will then focus on recent developments in the explicit treatment of the electrochemical interface [7], required for an understanding of charge transfer barriers, kinetics, and selectivity. I will discuss the scaling of CO2 reduction barriers, field effects, C-C coupling [8], and the integration of these effects into microkinetic models. Whipple, D. T. & Kenis, P. J. a. Prospects of CO 2 Utilization via Direct Heteroge- neous Electrochemical Reduction. J. Phys. Chem. Lett. 1, 3451–3458 (Dec. 2010). Graves, C., Ebbesen, S. D., Mogensen, M. & Lackner, K. S. Sustainable hydrocarbon fuels by recycling CO 2 and H 2 O with renewable or nuclear energy. Renewable and Sustainable Energy Reviews 15, 1–23 (2011). Nørskov, J. K., Rossmeisl, J., Logadottir, A., Lindqvist, L., Kitchin, J. R., Bligaard, T. & Jónsson, H. Origin of the Overpotential for Oxygen Reduction at a Fuel-Cell Cathode. J. Phys. Chem. B 108, 17886–17892 (Nov. 2004). Shi, C., Hansen, H. a., Lausche, A. C. & Nørskov, J. K. Trends in electrochemical CO2 reduction activity for open and close-packed metal surfaces. Phys. Chem. Chem. Phys. 16, 4720–7 (Mar. 2014). Kuhl, K. P., Hatsukade, T., Cave, E. R., Abram, D. N., Kibsgaard, J. & Thomas, F. Electrocatalytic conversion of carbon dioxide to methane and methanol on transition metal surfaces (2014). Chan, K., Tsai, C., Hansen, H. A. & Nørskov, J. K. Molybdenum sulfides and selenides as possible electrocatalysts for CO2 reduction. ChemCatChem 6, 1899–1905 (2014). Chan, K. & Nørskov, J. K. Electrochemical Barriers Made Simple. J. Phys. Chem. Lett. 2663–2668 (2015). Montoya, J. H., Shi, C., Chan, K. & Nørskov, J. K. Theoretical Insights into a CO Dimerization Mechanism in CO2 Electroreduction. The journal of physical chemistry letters 6, 2032–2037 (2015).

Experimentally Determined Ti-Al-Cl Phase Diagram at T = 150 to 400

Introduction The titanium aluminum chlorine, Ti-Al-Cl, system encompasses a range of current industrial processes and a number of processes currently under development. The major industries and processes are: TiCl4 production via high temperature chlorination of titanium oxide ore for the pigment industry, Ziegler-Natta catalysts, β-TiCl3(AlCl3)1/3 produced by Al driven reduction of TiCl4(l) for use in polypropylene production [1], Ti metal production via high temperature reduction of TiCl4 using metal reducing agents (Mg, Na, etc.) and Ti-Al alloy production for transport and chemical industries. Despite the importance of these processes, there are no published phase diagrams for the Ti-Al-Cl system and only limited thermodynamic data for TiCl3-AlCl3 and TiCl2-AlCl3 solution phases [2].A number of issues make this system difficult to study. The salts compounds react with H2O, O2 and many organic compounds and they can only be handled in clean glove boxes. The salts are volatile, form complex molecular species that are non-ideal; which make it difficult to identify the molecular species and measure their partial pressures [3,8]. Titanium and aluminium have a range of oxidation states (Ti: 4+, 3+, 2+ and Al: 3+, 2+, 1+), the stability of each oxidation state depend on the local chemical environment and a series of disproportionation reactions allow conversion between ions [3,4]. The unique properties of AlCl3(s) and Al2Cl6(l) result in the formation of a range of complex solution phases with TiCl3 and TiCl2 [2,4]. Many container materials react with these salts and Ti-Alloys at temperatures above 200°C [5]. Finally, it is difficult to prepare metallographic samples containing salt and metal for characterization via scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction needed for a phase equilibria study. However, recent work has solved a number of these experimental problems allowing an initial investigation of the phase equilibria in Ti-Al-Cl system. Experimental and Results The experiments consisted of mixing different amounts of high purity TiCl3(s) and AlCl3(s), loading the mixtures into a container, where the “sample” is the salt mixture plus the container. Multiple samples were loaded into wells a metal block that was sealed and a controlled over pressure of static high purity argon was supplied to limit vapour loss. The sealed metal block was loaded into the isothermal zone of a vertical tube furnace for annealing. (All sample preparation, loading and unloading was done inside a clean glove box.) To study salt / metal equilibrium pure-aluminium, pure-titanium and various Ti-Alloy containers were used. To study the equilibrium between the TiCl3-AlCl3 and TiCl2-AlCl3 pseudo binaries an Al2O3 container was used together with a small amount of Al(s).The samples were equilibrated at temperatures between 150 and 400°C for 50 ~ 200hr and quenched. After unloading the samples were mounted in epoxy and prepared for SEM and EPMA. All metallographic sample preparation and carbon coating was done inside a clean glove box. The prepared samples were transferred into the SEM / EPMA without exposure to air. Similarly, XRD sample preparation was performed inside a clean glove box, with powders mounted into a bespoke sample holder and sealed from exposure to air and moisture using Mylar film.This worked focused on determining the solubility range of nominally binary salt phases, TiCl3(s), TiCl2(s) and AlCl3(s) and the stability of ternary salts like TiAlCl5(s) [7] and Ti(AlCl4)2(s,l) [2-4,6] and determining phase compositions in three phase fields between: 1) TiCl3-AlCl3 and TiCl2-AlCl3 and 2) TiCl2-AlCl3 and Ti-Al. Results from initial experiments are reported as a number of isothermal sections between 150 and 400°C. References Brant, P. and E. G. M. Tornqvist, Inorganic Chemistry, 1986, 25(21): 3776-3779. Schafer, H. Angewandte Chemie International Edition, 1976, 15(12): 713-788. Sørlie, M. and H. A. Øye Inorganic Chemistry, 1978, 17(9): 2473-2484. Sørlie, M. and H. A. Øye. Inorganic Chemistry, 1981, 20(5): 1384-1390. Berg, R. W., H. A. Hjuler, et al. Inorganic Chemistry, 1984, 23(5): 557-565. Justnes, A., E. Rytter, et al. Polyhedron, 1982, 1(4): 393-396. Brynestad, J., S. von Winbush, et al. Inorganic and Nuclear Chemistry Letters, 1970, 6(12): 889-893. Hildenbrand, D. L., K. H. Lau, et al. Journal of Physical Chemistry, 1991, 95(8): 3435-3437.

Control of Lattice Orientation and Interface of LiCoO2 for All Solid State Batteries

All solid state batteries are widely investigated as next generation batteries because they do not suffer from leakage, volatilization, and flammability of liquid electrolyte. Both bulk type and thin film solid batteries have attract great attention. LiCoO2 thin film has been commonly used as the cathode material for solid state batteries due to its high capacity, operating voltage and long cycle life. Because of the importance of the solid-solid interface for the performance of the battery and stability during cycling, i.e. its life time, the interface of substrate/LiCoO2 and LiCoO2/solid electrolyte during the preparation of the solid battery and possible intermediate products in the interlayer attract great attention recently. [1] The deposition parameters has a big influence on the film quality in terms of structure, morphology and electrochemical properties. In the case of layered LiCoO2, lithium-ion diffusion rely on vacancy hopping mechanism within the lithium plane, showing a predominant two dimensional path. Therefore, different orientation of lattice could influence the intercalation properties of LiCoO2 thin film deposited. [2] A primary challenge in all solid state battery is the difficulty of rapidly moving charge across solid/solid interface within the electrodes and across the electrode/electrolyte interface. The consecutive study on electrode and/or electrolyte has achieved great progress for the last decades. However, interfaces still dominate the interfacial impedance during electrochemical reaction. The optimization of interface of substrate/LiCoO2 and LiCoO2 /solid electrolyte could direct the further improvement of current all solid state batteries. Both lithium ion mobility and electrochemical reaction of LiCoO2 thin film with the solid electrolyte and the substrate are related to the interfacial resistance, which could be minimized through controlling growth orientation of LiCoO2during deposition.[3] Therefore, the ionic transportation across solid/solid interface and electrode/electrolyte interface are increased, leading to improved electrochemical performance. In this work, we optimize the deposition parameter to get high crystalline HT-LiCoO2 with hexagonal structure and good electrochemical performance firstly. Next, we study on sputtering deposition of LiCoO2 with different orientation in order to study the LiCoO2/substrate and LiCoO2/solid state electrolyte interface. The compositional (XPS), microstructural (XRD, Raman, SEM) and electrochemical properties of the sputtering LiCoO2thin films with different orientation are investigated. For the study of interface, we will adopt advanced technique to investigate the chemical/physical changes at the interface layers. Reference [1] Luntz, Alan C., et al. The journal of physical chemistry letters 6.22 (2015): 4599-4604. [2] Bates, J. B., et al. Journal of The Electrochemical Society 147.1 (2000): 59-70. [3] Yoon, Yongsub, et al. Journal of Power Sources226 (2013): 186-190.

First-Principles Studies of Delithiation Mechanisms of Hybrid Li-Ion/Li-O2 Battery Materials

Lithium metal oxides with high Li2O contents, such as Li6MnO4, Li6CoO4 and Li5FeO4 , areof particular interest as novel, high capacity hybrid cathode materials due to their potential dual Li-ion/Li-O2 activity [1, 2]. Previous experiments on the charge process of Li5FeO4 have demonstrated a significant electrochemical capacity of 475 mAh/g in a Li-O2 cell[3]. However, the geometrical and electronic structure changes during the charge process remain elusive, and whether and how oxygen is evolved is uncertain. In this study, we employed first-principles density functional theory (DFT) to monitor the structural and energetic changes of hybrid batteries along various delithiation routes. Two delithiation routes of Li6MnO4, Li6CoO4 and Li5FeO4systems, namely Li removal and 2Li+O concerted removal, are investigated by DFT calculations. Step-by-step removals have been carried out and the stabilities of the Li and Li/O deficient systems are investigated based on DFT energies of each extraction step. The energetic competition between Li and oxygen removal is determined as a function of Li content and compared among the three systems. Bader charge analysis is used to compare charge compensation tendencies, upon delithiation, among Fe, Co and Mn. The implications of these results for other hybrid battery systems will be discussed. Acknowledgements This work was supported as a part of the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences under award number DE-AC02–06CH11. Use of the Advanced Photon Source, a US DOE Office of Science User Facility operated by Argonne National Laboratory, was supported by DOE under Contract No. DE-AC02-06CH11357. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Reference: M. M. Thackeray, M. K. Y. Chan, L. Trahey, S. Kirklin, and C. Wolverton, “Vision for Designing High-Energy, Hybrid Li Ion/Li-O2 Cells,” Journal of Physical Chemistry Letters 4, 3607 (2013).S. Kirklin, M. K. Y. Chan, L. Trahey, M. M. Thackeray, and C. Wolverton, “High-throughput screening of high-capacity electrodes for hybrid Li-ion/Li-O2 cells,” Physical Chemistry Chemical Physics 16, 22073 (2014).L. Trahey, C. S. Johnson, J. T. Vaughey, S.-H. Kang, L. J. Hardwick, S. A. Freunberger, P. G. Bruce, and M. M. Thackeray, “Activated Lithium-Metal-Oxides as Catalytic Electrodes for Li–O2 Cells,” Electrochemical and Solid-State Letters 14, A64-A66 (2011). The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The U.S. Government retains for itself, and others acting on its behalf, a paid-up nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.

The Li-Ion and Na-Ion Diffusion Mechanism in Halogen Substituted Solid Sulfide Electrolytes Studied by Solid State NMR and DFT Based Molecular Dynamics Simulations

Both Li-ion and Na-ion all solid state batteries are under development, where the absence of an liquid electrolyte potentially leads to improved safety and higher energy densities. Both the bulk ionic conductivity, as well as the conductivity over the electrolyte-electrolyte and electrolyte-electrode interfaces are prerequisites for efficient charge transport in solid state batteries. In many solid electrolytes the bulk mobility can be improved by introducing dopants that control the site occupancies by charge compensation. On the other hand the impact of solid-solid interfaces is anticipated to be one of the major bottlenecks towards high performance solid state batteries, making it of large importance to characterize the transport in detail. The present study provides detailed insight in the Na-ion and Li-ion conductivity in Na3PS4 1 and Li6PS5Cl2 sulfide solid electrolytes. The relative contribution of the bulk conductivity versus the conductivity over the solid-solid electrolyte and solid-solid electrolyte-electrode interfaces is revealed by comparing solid state NMR relaxation experiments with impedance spectroscopy. In addition X-ray and Neutron diffraction is performed to characterize the structures in detail. The structure and self diffusion measured by NMR is compared to DFT based Molecular Dynamics (MD) simulations that reveal the diffusion mechanism and the impact of halogen substitution in both cubic/tetragonal Na3PS4 (Na3-yPS4-yXy, X=Cl,Br,…) and argyrodite Li7PS6 (Li6PS5X, X=Cl,Br,…) structures. Solid state NMR relaxation experiments, shown in Figure 1c for Li6PS5Br, have the ability to directly probe the atomic scale Li-ion mobility in solid electrolytes and electrode materials3-6offering a non-destructive method to probe the self-diffusion coefficients. Conversion to solid state conductivities allows complementary information to impedance spectroscopy, for instance giving insight in the role of grain boundaries on the overall conductivity, as illustrated in Figure 1d. DFT MD-simulations, shown for Li6PS5Br in Figure 1a and 1b, allow to develop understanding of the diffusion mechanism of Li-ions and Na-ions in solid electrolytes and how these structures may be optimized to yield higher bulk conductivities. By systematically varying the halogen element to introduce Na-ion vacancies in both cubic/tetragonal Na3PS4 (Na3-yPS4-yXy, X=Cl,Br,…) and in argyrodite Li7PS6 (Li6PS5X, X=Cl,Br,…) structures, the simulations reveal the impact of vacancies and the host structure on the conductivity. This gives insight why and what halogen dopant results in optimal structural conditions to improve the Na-ion and Li-ion conductivity. By combining solid state NMR, Impedance, XRD and ND with DFT MD simulations, this study provides detailed insight in the Na-ion and Li-ion diffusion mechanism in in both cubic/tetragonal Na3PS4 (Na3-yPS4-yXy, X=Cl,Br,…) and argyrodite Li7PS6 (Li6PS5X, X=Cl,Br,…) solid electrolytes and potential routes to improve its performance in all solid state batteries. (1) Hayashi, A.; Noi, K.; Sakuda, A.; Tatsumisago, M. Nature Communications 2012, 3. (2) Deiseroth, H.-J.; Kong, S.-T.; Eckert, H.; Vannahme, J.; Reiner, C.; Zaiss, T.; Schlosser, M. Angewandte Chemie-International Edition 2008, 47, 755. (3) Wagemaker, M.; van Eck, E. R. H.; Kentgens, A. P. M.; Mulder, F. M. Journal of Physical Chemistry B 2009, 113, 224. (4) Wagemaker, M.; Kentgens, A. P. M.; Mulder, F. M. Nature 2002, 418, 397. (5) Schmidt, W.; Bottke, P.; Sternad, M.; Gollob, P.; Hennige, V.; Wilkening, M. Chemistry of Materials 2015, 27, 1740. (6) Epp, V.; Gun, O.; Deiseroth, H.-J.; Wilkening, M. Journal of Physical Chemistry Letters 2014, 4, 2118. (7) Tanibata, N.; Noi, K.; Hayashi, A.; Kitamura, N.; Idemoto, Y.; Tatsumisago, M. Chemelectrochem 2014, 1, 1130. Figure 1. (a) The Li-density and (b) Li-ion jumps for Li6PS5Br at 600 K from DFT molecular dynamics simulations. (c) 7Li NMR spin-lattice relaxation rates 1/T1 (at 155.506MHz) of Li6PS5Br which allows to deduce the hopping rate and activation energy for Li-ion self-diffusion. (d) Temperature-dependence of Li jump rates of Li6PS5Br obtained from MD calculations and deduced from 7Li static SLR NMR measurements. The dash line in the figure shows an Arrhenius activation energy of 0.18 eV for bulk self-diffusion and s indicates the macroscopic conductivity measured with impedance spectroscopy. The lower value of s implies that diffusion over the grain boundary between different Li6PS5Br grains is limiting the conductivity of Li6PS5Br electrodes. Figure 1

Greg Scholes Takes over as Deputy Editor of JPC Letters

A noted in an Editorial last month, Prashant Kamat has now left JPC Letters to become the Editor-in-Chief of a new ACS journal, ACS Energy Letters. Prashant did a terrific job for JPC, first as Senior Editor and then taking over as Deputy Editor when JPCL was founded in 2010. We wish him well in his new position. I am delighted to announce that Greg Scholes has taken over as Deputy Editor in his place. Greg is currently the William S. Tod Professor of Chemistry at Princeton University, and he has been Senior Editor of JPC since 2009 and of JPCL since 2011. Dr. Scholes is a distinguished researcher who has contributed important research in several areas that relate to JPC, including both theory and experiment as related to photoprocesses in biological systems and materials. He has contributed important results concerning processes in solar energy conversion, in photopolymers, and in semiconductor nanocrystals. Among his accomplishments are key insights concerning the importance of coherence in the light-harvesting mechanism in photosynthesis and seminal contributions concerning multidimensional electronic spectroscopy. These accomplishments demonstrate the breadth and depth that Greg brings to this position, and it indicates the leadership that we can expect from Greg in his new role. Please join me in welcoming Greg to this important position. George Schatz The Journal of Physical Chemistry Letters grew and flourished under the leadership of Prashant Kamat. He was incredibly successful at building a high impact factor and, at the same time, expediting publication. This has been made possible in part by optimizations and the enthusiasm introduced by Prashant in collaboration with the ACS publications team and particularly by the support from superb authors, referees, and editors. Editors are engaged in the science of our authors and work as a team to ensure consistent high quality and articles sent for review. There are many nuancesas well as positives and negativesto this entire process, which is a broad challenge for the journal. Nevertheless, the net result is important because it rewards authors and inspires readers. Overall, JPCL has become a journal of choice for reporting the leading edge of physical chemistry research, and it is thereby well-positioned to help authors shape the future of our field. With that in mind, an opportunity is to work out new ways to highlight exceptional papers in each issue in order to promote that research and its consequences to a wider readership. I am delighted to have the chance to help the journal, and I look forward to working with a terrific JPCL team, authors, and referees to promote and enhance the field of physical chemistry. Greg Scholes George C. Schatz Northwestern University, Evanston Illinois 60201, United States Greg Scholes Princeton University, Princeton, New Jersey 08544, United States ■ AUTHOR INFORMATION Notes Views expressed in this editorial are those of the author and not necessarily the views of the ACS.

(Invited) Comparative First Principles Studies of Hybrid Li-Ion/Li-Oxygen Battery Materials

In the Center for Electrochemical Energy Science (CEES) Energy Frontier Research Center, we are investigating a new class of energy storage materials – hybrid Li-ion/Li-oxygen materials – that combine transition metal and oxygen redox chemistries to deliver high energy storage capacity [1, 2, 3]. The electrochemical reactions, structural and electronic structure evolution of these materials are complex, requiring a combination of in-depth characterization and first principles modeling. In this talk, we will report on a comparison study of several examples of hybrid Li-ion/Li-oxygen materials using density functional theory calculations. We will discuss the structural and electronic structure reasons for differences in reaction pathways and competition between transition metal vs oxygen redox chemistries. Insight towards selecting and designing promising hybrid battery materials gleaned from the comparison will be discussed. [1] L. Trahey, C. S. Johnson, J. T. Vaughey, S.-H. Kang, L. J. Hardwick, S. A. Freunberger, P. G. Bruce, M. M. Thackeray, “Activated Lithium-Metal-Oxides as Catalytic Electrodes for Li-O2 Cells,” Electrochemical and Solid-State Letters, 2011, 14, A64. [2] M. M. Thackeray, M. K. Y. Chan, L. Trahey, S. Kirklin, and C. Wolverton, “Vision for Designing High-Energy, Hybrid Li Ion/Li–O2 Cells,” Journal of Physical Chemistry Letters, 2013, 4, 3607. [3] Z. Yang, L. Trahey, Y. Ren, M. K. Y. Chan, C. Lin, J. Okasinski, and M. M. Thackeray, “In-Situ High-Energy Synchrotron X-ray Diffraction Studies and First Principles Modeling of α-MnO2 Electrodes in Li-O2 and Li-ion Coin Cells,” Journal of Materials Chemistry A, 2015, 3, 7389.

Single- and Few-Layers MoSe2 Nanoflowers: Synthesis, Characterization, and Their Piezoresponse

We demonstrate a hydrothermal process at temperature of 180oC to synthesize a single to few layers MoSe2 nanoflowers which exhibit a high surface-to-volume ratio and is stable under room temperature in ambient air. The crystal structure of the MoSe2 nanoflowers has been confirmed by X-ray diffraction pattern, Raman, and High-resolution transmission electron microscopy (HRTEM). On the basis of the scanning electron microscope (SEM) image, the size of the MoSe2 nanoflowers is in the range of the 300-500nm. HRTEM image reveals that the MoSe2 nanoflowers possess a great number of the single- and few-layers, which further confirms that our nanoflowers display the plentiful amount of active surface sites. In addition, the lattice fringes between each single layer is about 0.66 nm, which is slightly larger than the reported value of 0.62 nm for the MoSe2. The piezoresponse force microscopy image further shows that the MoSe2 nanoflowers exhibits significantly piezoelectric potential which is generated from the active surface sites of the petals in the MoSe2 nanoflowers. Reference[1-6] 1. Duerloo, K.-A.N., M.T. Ong, and E.J. Reed, Intrinsic piezoelectricity in two-dimensional materials. The Journal of Physical Chemistry Letters, 2012. 3(19): p. 2871-2876. 2. Kaasbjerg, K., K.S. Thygesen, and A.-P. Jauho, Acoustic phonon limited mobility in two-dimensional semiconductors: Deformation potential and piezoelectric scattering in monolayer MoS 2 from first principles. Physical Review B, 2013. 87(23): p. 235312. 3. Alyörük, M.M., et al., Promising Piezoelectric Performance of Single Layer Transition-Metal Dichalcogenides and Dioxides. The Journal of Physical Chemistry C, 2015. 119(40): p. 23231-23237. 4. Qi, J., et al., Piezoelectric effect in chemical vapour deposition-grown atomic-monolayer triangular molybdenum disulfide piezotronics. Nature communications, 2015. 6. 5. Wu, T. and H. Zhang, Piezoelectricity in Two ‐ Dimensional Materials. Angewandte Chemie International Edition, 2015. 54(15): p. 4432-4434. 6. Chhowalla, M., et al., The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets. Nature chemistry, 2013. 5(4): p. 263-275.

Biodegradation of Organophosphonates by Aspergillus Specie

Oriental Journal of Chemistry is a peer reviewed quarterly research journal of pure and applied chemistry. It publishes standard research papers in almost all thrust areas of current chemistry of academic and commercial importance. It provides a platform for rapid publication of quality research papers, reviews and chemistry letters. Oriental Journal of Chemistry is abstracted and indexed in almost all reputed National and International agencies.

Determination of Cyproheptadine hydrochloride in Pure and Pharmaceutical forms : A Spectrophotometric study

Oriental Journal of Chemistry is a peer reviewed quarterly research journal of pure and applied chemistry. It publishes standard research papers in almost all thrust areas of current chemistry of academic and commercial importance. It provides a platform for rapid publication of quality research papers, reviews and chemistry letters. Oriental Journal of Chemistry is abstracted and indexed in almost all reputed National and International agencies.

Litdi As Electrolyte Salt for Li-Ion Batteries: Transport Properties in EC/Dmc and Cyclability of Li/Graphite and Li/LiFePO4 Half Cells

The lithium-ion battery (LiB) technology has become over the years one of the most popular type of rechargeable batteries for portable electronics [1]. Now in a world knowing a progressive electrification of transport systems the LiBs are growing in popularity for large-scale applications such as electric vehicles. Therefore the continuing success and progress of the LiB technology depends on the careful choice of the battery components such as the electrolyte [2-4]. It is needless to say that the electrolyte is a very important component in batteries as it allows ionic movements, and should maintain its functions over its life-span without presenting safety risks, especially when damaged. The most commonly used electrolytes are lithium hexafluorophosphate (LiPF6) dissolved in mixtures of alkylcarbonate solvents. LiPF6 is actually the reference Li-salt for LiB due to its numerous convenient properties [3, 5, 6]. However its thermal instability and moisture sensitivity, which induce high risks of releasing HF via the hydrolysis of the PF6 - anion, have been highly criticized justifying the importance in finding a replacement. The new 4,5-dicyano-2-trifluoromethyl-imidazolide (TDI-) anion is a promising anion for lithium salt which will be used in future energy storage systems such as lithium-ion batteries. Here we will compare LiTDI solutions in EC/DMC (50:50 wt %) to competing salts like LiTFSI, LiFAP and the commonly used LiPF6, known for its numerous advantageous properties, in the same solvent mixture. LiTDI in EC/DMC exhibits the lowest viscosity among the investigated electrolytes, and a fair conductivity of 6.84 mS.cm-1 at 25°C (1mol.L-1). LiTDI also displays in EC/DMC a higher transference number than LiPF6 in the same solvent mixture which is interesting since only the current carried by the lithium ions is useful. LiTDI, as many other lithium salts, is not completely dissociated in EC/DMC and an estimation of the ion-pair dissociation coefficient was achieved by using the Walden rule. An estimation was also calculated for LiTFSI, LiFAP and LiPF6. In order to evaluate the performance of the LiTDI-EC/DMC electrolyte for use in Li-ion batteries, Li/graphite and Li/LiFePO4 half-cell systems have been investigated. Despite an important irreversible capacity within the lithium/graphite half-cell during the first charge-discharge cycle, a reasonable average reversible capacity has been obtained at a low cycling-rate (C/24) and easily repeated after 30 cycles. The obtained capacity was also higher than for LiTFSI and LiFAP based electrolytes in the same conditions. Nevertheless, at higher cycling-rates the performance of the LiTDI based electrolyte is not as good as LiPF6, even though the coulombic efficiencies range from 99.5% and 100%. A more resistive or/and thicker solid electrolyte interface (SEI) was identified as the cause of capacity loss in LiTDI half-cell. Tests are on the way (XPS, EDX, EIS and EQCM) to investigate the composition and characteristics of the SEI formed in the presence of LiTDI. Several additives have also been tested by addition to the electrolyte mixture and their impact on the SEI observed. Lithium/LiFePO4 half-cells exhibit good capacity retention over 100 cycles at low rate (150 mA.h.g-1 at C/24) which does not drop too much when cycling at a C/2 (128 mA.h.g-1). [1] E. M. Erickson, C. Ghanty, and D. Aurbach, "New Horizons for Conventional Lithium Ion Battery Technology," The Journal of Physical Chemistry Letters, vol. 5, pp. 3313-3324, 2014/10/02 2014. [2] H. Duncan, N. Salem, and Y. Abu-Lebdeh, "Electrolyte Formulations Based on Dinitrile Solvents for High Voltage Li-Ion Batteries," Journal of The Electrochemical Society, vol. 160, pp. A838-A848, 2013. [3] G. G. Eshetu, S. Grugeon, G. Gachot, D. Mathiron, M. Armand, and S. Laruelle, "LiFSI vs. LiPF6 electrolytes in contact with lithiated graphite: Comparing thermal stabilities and identification of specific SEI-reinforcing additives," Electrochimica Acta, vol. 102, pp. 133-141, 2013. [4] L. Niedzicki, G. Z. Żukowska, M. Bukowska, P. Szczeciński, S. Grugeon, S. Laruelle, M. Armand, S. Panero, B. Scrosati, M. Marcinek, and W. Wieczorek, "New type of imidazole based salts designed specifically for lithium ion batteries," Electrochimica Acta, vol. 55, pp. 1450-1454, 2010. [5] J. S. Gnanaraj, M. D. Levi, Y. Gofer, D. Aurbach, and M. Schmidt, "LiPF3(CF2CF3)(3): A salt for rechargeable lithium ion batteries," Journal of The Electrochemical Society, vol. 150, pp. A445-A454, 2003. [6] M. Dahbi, F. Ghamouss, F. Tran-Van, D. Lemordant, and M. Anouti, "Comparative study of EC/DMC LiTFSI and LiPF6 electrolytes for electrochemical storage," Journal of Power Sources, vol. 196, pp. 9743-9750, 2011.