Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session B11: Energy Storage Methods |
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Sponsoring Units: GERA Chair: Timo Thonhauser, Wake Forest University Room: A107-A109 |
Monday, March 15, 2010 11:15AM - 11:27AM |
B11.00001: Flexible symmetric supercapacitors based on vertical TiO$_{2 }$and carbon nanotubes C.J. Chien, Pai-chun Chang, Jia G. Lu Highly conducting and porous carbon nanotubes are widely used as electrodes in double-layer-effect supercapacitors. In this presentation, vertical TiO2 nanotube array is fabricated by anodization process and used as supercapacitor electrode utilizing its compact density, high surface area and porous structure. By spin coating carbon nanotube networks on vertical TiO2 nanotube array as electrodes with 1M H$_{2}$SO$_{4}$ electrolyte in between, the specific capacitance can be enhanced by 30{\%} compared to using pure carbon nanotube network alone because of the combination of double layer effect and redox reaction from metal oxide materials. Based on cyclic voltammetry and galvanostatic charge-discharge measurements, this type of hybrid electrode has proven to be suitable for high performance supercapacitor application and maintain desirable cycling stability. The electrochemical impedance spectroscopy technique shows that the electrode has good electrical conductivity. Furthermore, we will discuss the prospect of extending this energy storage approach in flexible electronics. [Preview Abstract] |
Monday, March 15, 2010 11:27AM - 11:39AM |
B11.00002: Structure and Capacitance of Electrical Double Layers inside Micropores Guang Feng, Rui Qiao, Jingsong Huang, Bobby G. Sumpter , Vincent Meunier Recent experiments indicate that the specific capacitance of micropores (diameter less than 2nm) increases anomalously as the pore size decreases$^{[1]}$. To understand the physical origin of this discovery, we performed a series of molecular dynamics simulations to study the electrical double layers (EDLs) in micropores with different shapes (tube vs slit) and pore sizes (0.668nm - 3.342nm). Several different aqueous electrolytes (K$^{+}$, Na$^{+}$, Cl$^{-}$, and F$^{-}$ in water) were used in these micropores. We quantified the structure of EDLs inside the pores, and computed the capacitance of EDLs. The scaling of capacitance shows a qualitative agreement with the experimental observations. We attribute the anomalous enhancement of capacitance in micropores to the short-range ionelectrode and ionsolvent interactions.[1] J. Chmiola, G. Yushin, Y. Gogotsi, C. Portet, P. Simon, and P.L. Taberna, Science 2006, 313, 1760. [Preview Abstract] |
Monday, March 15, 2010 11:39AM - 11:51AM |
B11.00003: Effects of Anisotropic Coherency Strain on Intercalation in Phase-Separating Crystals Liam Stanton, Martin Bazant We consider the self-organization of intercalating particles within crystals induced by spinodal decomposition and the anisotropy of coherency strains, motivated by recent Li-ion battery materials. A phase-field model is developed which incorporates the energetic contributions from the entropy, enthalpy and elastic properties of the host material. Bulk dynamics of the system is then analyzed using linear stability theory to obtain spinodal regions in the parameter space, and numerical simulations are used to predict long-term evolution and relaxational steady-states. These results may explain the alignment of the phase boundary with phosphate planes in LiFePO4, as assumed in recent models and observed in experiments. [Preview Abstract] |
Monday, March 15, 2010 11:51AM - 12:03PM |
B11.00004: \textit{In situ} nonresonant inelastic x-ray scattering spectra of LiCoO$_{2}$ battery electrodes Kenneth Nagle, Mali Balasubramanian, Swati Pol, Gerald Seidler, Christopher Johnson The rational design of improved battery electrodes for Li-ion batteries faces many barriers, not the least of which is a correct, fundamental understanding of the changes in local electronic structure that accompany insertion and removal of lithium. We present nonresonant inelastic x-ray scattering (NIXS) spectra from the 2$p$, 3$s$, and 3$p$ initial states in Co and the 1$s$ initial state in O from LiCoO$_{2}$ cathodes from working electrochemical cells. These spectra were measured using the lower energy resolution inelastic x-ray scattering (LERIX) spectrometer at the Advanced Photon Source. NIXS at $\sim $1 eV energy resolution provides a bulk-sensitive alternative to x-ray absorption spectroscopy for studies of low-energy ($<$1.5 keV) electronic transitions. Furthermore, at sufficiently high momentum transfers NIXS is sensitive to dipole-forbidden transitions, providing additional information about electronic structure. [Preview Abstract] |
Monday, March 15, 2010 12:03PM - 12:15PM |
B11.00005: Structural and electrochromic properties of Fe$_{2}$(SO$_{4})_{3}$ nanostructures prepared by template assisted method M.B. Sahana, Sudakar Chandran, Ratna Naik, Vaman Naik Oxides containing polyanions such as XO$_{4}^{2-}$ (X = S, Mo, P and W) as lithium insertion hosts are promising cathode materials due to their high thermal stability. However, the larger separation of the transition metal ions can be expected to reduce the electron mobility. As observed in LiFePO$_{4}$, this can be overcome either by coating the cathode materials with carbon or by decreasing the particle size. We have prepared nanowires of NASICON type structure and platelets of monoclinic Fe$_{2}$(SO$_{4})_{3}$ by template assisted electro deposition. These structures were grown on stainless steel substrates and are characterized by XPS, HRTEM, and XRD analysis. Both NASICON and monoclinic Fe$_{2}$(SO$_{4})_{3}$ structures are very porous and are comprised of nanoparticles leading to a high lithium insertion capacity. [Preview Abstract] |
Monday, March 15, 2010 12:15PM - 12:27PM |
B11.00006: Electromechanical Energy Transduction for Hybrid Vehicles Sridhar Reddy Vanja, Michael W. Kelly, A.N. Caruso Hybrid vehicle technology seeks to reduce the total energy consumption used for vehicle locomotion by recovering and reutilizing kinetic energy that is otherwise unrecovered or dissipated in conventional vehicle deceleration. The goal of the work is to determine the transduction mechanisms that work towards a Carnot efficiency without considering constraints or limitations placed by cost or materials. Specifically, this talk will present ideal thermodynamic models of energy exchange between mechanical, electrostatic, electromechanical and electrochemical devices with a goal of projecting an ideal hybrid vehicle. [Preview Abstract] |
Monday, March 15, 2010 12:27PM - 12:39PM |
B11.00007: Non-mean-field theory of anomalously large capacitance at the metal/ionic conductor interface Brian Skinner, Matt Loth, Boris Shklovskii Recent experiments on capacitors made with ion-conducting glasses have demonstrated a remarkably high capacitance at the metal/glass interface [1]. Such large capacitance cannot be explained by mean-field theories of the ionic double layer, since it implies a double-layer thickness that is significantly smaller than the ion radius. We propose an alternate theory of the ionic double-layer which allows for the binding of discrete ions to their image charges in the metal. We show that at small voltages the capacitance of the double-layer is limited only by the relatively weak dipole-dipole repulsion between bound ions. At large voltages the depletion of bound ions from one of the capacitor electrodes triggers a collapse of the capacitance to a much smaller value, in agreement with experiment. [1] C. R. Mariappan, T. P. Heins, and B. Roling, arxiv:cond-mat/0904.3856v2 [Preview Abstract] |
Monday, March 15, 2010 12:39PM - 12:51PM |
B11.00008: \textit{In-Situ }X-ray Absorption Spectroscopy Study of Li[LiMnNi]O2 Cathode Material Cherno Jaye, Faisal M. Alamgir, Nicole Leifer, Jay Whitacre, Steve G. Greenbaum The cation/Li substituted Li[LiM]O2 layered material (where M is typically a blend of Mn, Ni and Co) is a promising high-capacity Li-ion battery cathode material due to the fact that it has yielded capacities exceeding 240 mAh/g, and up to 285 mAh/g even after many (50) deep-discharge cycles at useable charge/discharge rates (C/20). In an effort to understand the origin and relevance of the substantial irreversible capacity observed during the first charge cycle at a potential of approximately 4.5 V vs. Li, we have performed an \textit{in-situ }x-ray absorption spectroscopy (XAS) study of the charge compensation mechanism associated with the charge/discharge of Li[LiMnNi]O2 cathode material. XAS at the Ni and Mn K edges were carried out during the first two charge cycles of a layered Li[Li0.17Mn0.58Ni0.25]O2 powder based electrode system using an in-situ cell. The XAS results provide information about the electronic and atomic structure around the metals as a function of state of charge. [Preview Abstract] |
Monday, March 15, 2010 12:51PM - 1:03PM |
B11.00009: First-principles stability study of clathrate hydrates under pressure Timo Thonhauser, Qi Li, Brian Kolb We present a first-principles DFT study of the structural stability of clathrate hydrates under pressure. These materials form under high pressure and low temperature and consist of polyhedral water cages that form an ice-like framework of hydrogen bonds. Clathrate hydrates can be filled with guest molecules such as methane or molecular hydrogen, in which case these materials and their stability are of interest for energy-storage solutions. Since the interactions between the water molecules themselves---but also between the water molecules and the guest molecules---is at least partly determined by van der Waals forces, we utilize the recently developed self-consistent van der Waals density functional vdW-DF (T. Thonhauser, V.R. Cooper, S. Li, A. Puzder, P. Hyldgaard, and D.C. Langreth, Phys. Rev. B 76, 125112 (2007)). For our simulations we consider the empty host lattice, as well as the host lattice filled with methane and molecular hydrogen, for pressures up to 1 GPa. Our results show that the system undergoes phase transitions from \emph{structure I} to \emph{structure II} and finally to \emph{structure H}, in good agreement with experiment. [Preview Abstract] |
Monday, March 15, 2010 1:03PM - 1:15PM |
B11.00010: Supercapacitors: Ferroelectric Polymer-Ceramic Nanoparticle Composite Films for Use in the Capacitive Storage of Electrical Energy Dana Parsons, Andrew Pierce, Tim Porter, Randy Dillingham, David Cornelison Most new alternative energy solutions including wind and solar power, will require short term energy storage for widespread implementation. One means of storage would be the use of capacitors owing to their rapid delivery of power and longevity compared to chemical batteries. Capacitor materials exhibiting high dielectric permittivity and breakdown strength, as well as light weight and environmental safety are most desirable. Recently, new classes of capacitor dielectric materials, consisting of ferroelectric polymer matrices containing ceramic nanoparticles have attracted renewed interest due to their high potential energy storage, charge and discharge properties and lightweight. In this study, polyvinylidene flouride (PVDF) thin films containing nanoparticles of the ceramic titanium dioxide created using a physical vapor deposition process, are analyzed for use as dielectrics for a supercapacitor. Measured results of the film parameters including dielectric properties and breakdown voltages will be presented. These parameters will be analyzed with respect to film characteristics such as, dispersion of the ceramic particles, thickness of the films and composition ratios. [Preview Abstract] |
Monday, March 15, 2010 1:15PM - 1:27PM |
B11.00011: Record Methane Storage in Monolithic and Powdered Activated Carbons YuChoong Soo, E. Nordwald, B. Hester, J. Romanos, B. Isaacson, D. Stalla, D. Moore, M. Kraus, J. Burress, E. Dohnke, P. Pfeifer The Alliance for Collaborative Research in Alternative Fuel Technology (ALL-CRAFT) has developed activated carbons from corn cob as adsorbent materials for methane gas storage by physisorption at low pressures. KOH activated carbons were compressed into carbon monolith using chemical binders. High pressure methane isotherms up to 250 bar at room temperature on monolithic and powdered activated carbons were measured gravimetrically and volumetrically. Record methane storage capacities of 250 g CH4/kg carbon and 130 g CH4/liter carbon at 35 bar and 293 K have been achieved. BET surface area, porosity, and pore size distributions were measured from sub-critical nitrogen isotherms. Pore entrances were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A prototype adsorbed natural gas (ANG) tank, loaded with carbon monoliths, was tested in Kansas City. [Preview Abstract] |
Monday, March 15, 2010 1:27PM - 1:39PM |
B11.00012: Adsorption of methane-mercaptane mixtures in carbon nanopores M. Golebiowska, L. Firlej, B. Kuchta, M. Roth, C. Wexler Natural gas is a widely-available but underutilized fuel, in particular for vehicular applications. An attractive alternative to compression is to store methane by physisorption into a suitable substrate (adsorbed natural gas, ANG). Currently there exists several materials that store methane efficiently at room temperature even at moderate pressures, e.g., nanoporous carbon$^1$. For easy detection of leaks low concentrations of thiols (mercaptans) are utilized since their threshold for detection by humans is in the PPB. Whereas pure methane adsorption has been extensively studied, understanding of adsorption of methane-mercaptane mixtures is required for the development of ANG systems. Here we present results of Molecular Dynamics simulations of the adsorption of methane-methylmercaptan and methane-ethylmercaptan mixtures carbon. We discuss thiols trajectories during adsorption-desorption cycle and reversibility of their adsorption in the presence of methane. Adsorption is simulated directly in a two-phase system (gas phase remains in equilibrium with the adsorbed phase). \noindent $^1$ P. Pfeifer, et al., Mater. Res. Soc. Symp. Proc. 1041, R02-02 (2008). [Preview Abstract] |
Monday, March 15, 2010 1:39PM - 1:51PM |
B11.00013: Toward Molecular Solar-Thermal Energy Storage: Systematic Search for New Molecular Systems Engin Durgun, Varadharajan Srinivasan, Yosuke Kanai, Gordon Wintrop , Jeffrey C. Grossman In the currently intensifying quest to harness solar energy for the powering of our planet, many efforts are centered around photo-induced generic charge separation, such as in photovoltaics, water splitting, and biologically inspired photosynthetic systems. An attractive alternative strategy would be to trap solar energy in the form of chemical bonds, ideally through the photo-conversion of a suitable molecule to a higher energy isomer, which, in turn, releases the stored energy by thermal reversal. Inspired by the discovery and investigations of fulvane-diruthenium, we explore strategies to discover new organometallic complexes that possess superior properties than organic molecules. We systematically search for complexes which are robust to storage cycles, easy to synthesize, tunable and which have high storage capacity and low UV excitation energies. Our analysis reveals that good organometallic candidates for solar-thermal energy storage systems can be identified and their performance can be improved through chemical substitution. [Preview Abstract] |
Monday, March 15, 2010 1:51PM - 2:03PM |
B11.00014: Experimental and theoretical study on hydrogen interaction with unsaturated Metal Organic Frameworks Nour Nijem, Jean Fran\c{c}ois Veyan, Yonggang Zhao, Lingzhu Kong, Jing Li, David C. Langreth, Yves J. Chabal Infrared absorption spectroscopy (IRAS) is useful to study the interaction of H$_{2}$ molecules inside various materials, since the frequency of its internal stretch mode depends on the adsorption site. Unsaturated Metal Organic Frameworks (MOFs) are particularly interesting due to their high H$_{2}$ uptakes with relatively large isosteric heats of adsorption (Q$_{st }>$8 kJ/mol). Our study focuses on H$_{2}$ in M$_{2}$(dhtp), dhtp=2,5-dihydroxyterephthalate (M= Zn, Ni, Co, Mg) and combines temperature-dependent IRAS measurements and vdW-DF calculations. Results show that the H$_{2}$ stretch frequencies are very sensitive to the chemical environment, with no correlation between binding energies and frequency shifts, as previously observed for saturated MOFs.\footnote{ N. Nijem \textit{et al.} submitted to J.A.C.S 2009} Moreover, the H$_{2}$ stretch vibration closest to the metal site exhibits a strong shift from -30 cm$^{-1}$ to -68 cm$^{-1}$ upon population of neighboring sites (e.g. ``oxygen'' site). [Preview Abstract] |
Monday, March 15, 2010 2:03PM - 2:15PM |
B11.00015: Bio-Inspired Catalyst for CO$_{2}$ Reduction Adonis Bovell, Kurt Warncke A catalytic device for high specificity recognition and light-driven reduction of CO$_{2}$ to energy rich biofuels is being developed by using the robust TIM barrel fold of the EutB subunit of the enzyme, ethanolamine-ammonia lyase (from \textit{Salmonella typhimurium}), as a scaffold. The cobalt(I) form of the native cobalamin serves as the catalytic center. Results show that cobalamins bind with optimal micromolar affinity to purified EutB, and undergo reductive activation. Molecular biology techniques have been used to generate histidine-tagged EutB subunit for high throughput mutagenesis studies. Rational active site modifications of EutB have been made to satisfy the criteria of specific CO$_{2}$ binding, reduction, and proton delivery. [Preview Abstract] |
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