Bulletin of the American Physical Society
APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014; Denver, Colorado
Session J25: Focus Session: Materials for Electrochemical Energy Storage: Layered Materials and Capacitors |
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Sponsoring Units: DMP GERA DCOMP Chair: Natalie Holzwarth, Wake Forest University Room: 503 |
Tuesday, March 4, 2014 2:30PM - 2:42PM |
J25.00001: Origins of Lithium-Carbon Binding in Carbon-based Lithium-ion Battery Anodes Brandon Wood, Yuanyue Liu, Morris Wang, Boris Yakobson Many key performance characteristics of carbon-based lithium-ion battery anodes are determined by the strength of binding between lithium (Li) and $sp^2$ carbon (C). Using extensive density functional theory calculations, we investigate the detailed interaction of Li with a wide variety of $sp^2$ C substrates, including pristine, defective, and strained graphene; planar C clusters; nanotubes; C edges; and multilayer stacks. We find that in almost all cases, the Li-C binding energy scales is determined largely by the work required to fill unoccupied carbon states, suggesting that intrinsic quantum capacitance is important for predicting Li capacity. This allows the binding energy and capacity to be estimated based solely on the electronic structure of the substrate. It also provides a connection to carbon-based supercapacitors, and underscores the role of electronic structure in interfacial electrochemical systems. Implications for improving the effective capacity of carbon-based anodes will be discussed. This work was performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344. [Preview Abstract] |
Tuesday, March 4, 2014 2:42PM - 2:54PM |
J25.00002: Fe-catalyzed carbon nanotubes for high-energy density carbon-based supercapacitors Robert Emmett, Mehmet Karakaya, Mark Roberts, Margarita Arcilla-Velez, Ramakrishna Podila, Apparao Rao Carbon nanotubes (CNTs) are one of the most suitable supercapacitor electrode materials due to their high mechanical strength, electrical conductivity, and surface area. Albeit these unique properties of CNTs, energy density of carbon-based double layer capacitors is limited by the inability of CNTs to actively participate in redox processes. Here, we show that electrochemical characteristics of CNTs can be improved by activating the residual Fe catalyst to participate in Faradaic charge storage via Fe$^{\mathrm{2+}}$ -\textgreater Fe$^{\mathrm{3+}}$ redox process. By using traditional liquid injection chemical vapor deposited CNTs which contains 5.7 wt.{\%} residual Fe catalyst (R. Andrews et al.,, \textit{Chem. Phys. Letters},~\textbf{303}, 467-474 (1999)), the capacitance of CNT electrodes can be increased from 20 F/g to 150 F/g, in the range of -0.2 to 1.2 V. The use of Fe containing CNTs to manufacture supercapacitor electrodes with increased energy density and charge capacity of with high charge/discharge rates with extremely long-term cycle stability will be discussed. [Preview Abstract] |
Tuesday, March 4, 2014 2:54PM - 3:06PM |
J25.00003: Performance of Liquid Phase Exfoliated Graphene As Electrochemical Double Layer Capacitors Electrodes Jacob Huffstutler, Milinda Wasala, Julianna Richie, Andrew Winchester, Sujoy Ghosh, Swastik Kar, Saikat Talapatra We will present the results of our investigations of electrochemical double layer capacitors (EDLCs) or supercapacitors (SC) fabricated using liquid-phase exfoliated graphene. Several electrolytes, such as aqueous potassium hydroxide KOH (6M), ionic 1-Butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF$_{6}$], and ionic 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate[BMP][FAP] were used. These EDLC's show good performance compared to other carbon nanomaterials based EDLC's devices. We found that the liquid phase exfoliated graphene based devices possess specific capacitance values as high as 262 F/g, when used with ionic liquid electrolyte[BMP][FAP], with power densities ($\sim$ 454 W/kg) and energy densities ($\sim$ 0.38Wh/kg). Further, these devices indicated rapid charge transfer response even without the use of any binders or specially prepared current collectors. A detailed electrochemical impedance spectroscopy analysis in order to understand the phenomenon of charge storage in these materials will be presented. [Preview Abstract] |
Tuesday, March 4, 2014 3:06PM - 3:18PM |
J25.00004: Roll-to-Roll production of carbon nanotubes based supercapacitors Jingyi Zhu, Anthony Childress, Mehmet Karakaya, Mark Roberts, Margarita Arcilla-Velez, Ramakrishna Podila, Apparao Rao Carbon nanomaterials provide an excellent platform for electrochemical double layer capacitors (EDLCs). However, current industrial methods for producing carbon nanotubes are expensive and thereby increase the costs of energy storage to more than {\$}10 Wh/kg. In this regard, we developed a facile roll-to-roll production technology for scalable manufacturing of multi-walled carbon nanotubes (MWNTs) with variable density on run-of-the-mill kitchen Al foils. Our method produces MWNTs with diameter (heights) between 50-100 nm (10-100 $\mu$m), and a specific capacitance as high as $\sim$ 100 F/g in non-aqueous electrolytes. In this talk, the fundamental challenges involved in EDLC-suitable MWNT growth, roll-to-roll production, and device manufacturing will be discussed along with electrochemical characteristics of roll-to-roll MWNTs. [Preview Abstract] |
Tuesday, March 4, 2014 3:18PM - 3:30PM |
J25.00005: Biopolymer-nanocarbon composite electrodes for use as high-energy high--power density electrodes Mehmet Karakaya, Mark Roberts, Margarita Arcilla-Velez, Jingyi Zhu, Ramakrishna Podila, Apparao Rao Supercapacitors (SCs) address our current energy storage and delivery needs by combining the high power, rapid switching, and exceptional cycle life of a capacitor with the high energy density of a battery. Although activated carbon is extensively used as a supercapacitor electrode due to its inexpensive nature, its low specific capacitance (100-120 F/g) fundamentally limits the energy density of SCs. We demonstrate that a nano-carbon based mechanically robust, electrically conducting, free-standing buckypaper electrode modified with an inexpensive biorenewable polymer, viz., lignin increases the electrode's specific capacitance ($\sim$ 600-700 F/g) while maintaining rapid discharge rates. In these systems, the carbon nanomaterials provide the high surface area, electrical conductivity and porosity, while the redox polymers provide a mechanism for charge storage through Faradaic charge transfer. The design of redox polymers and their incorporation into nanomaterial electrodes will be discussed with a focus on enabling high power and high energy density electrodes. [Preview Abstract] |
Tuesday, March 4, 2014 3:30PM - 3:42PM |
J25.00006: Structure of Room Temperature Ionic Liquids on Charged Graphene: An integrated experimental and computational study Ahmet Uysal, Hua Zhou, Sang Soo Lee, Paul Fenter, Guang Feng, Song Li, Peter Cummings, Pasquale Fulvio, Sheng Dai, Jake McDonough, Yury Gogotsi Electrical double layer capacitors (EDLCs) with room temperature ionic liquid (RTIL) electrolytes and carbon electrodes are promising candidates for energy storage devices with high power density and long cycle life. We studied the potential and time dependent changes in the electric double layer (EDL) structure of an imidazolium-based room temperature ionic liquid (RTIL) electrolyte at an epitaxial graphene (EG) surface. We used \textit{in situ} x-ray reflectivity (XR) to determine the EDL structure at static potentials, during cyclic voltammetry (CV) and potential step measurements. The static potential structures were also investigated with fully atomistic molecular dynamics (MD) simulations. Combined XR and MD results show that the EDL structure has alternating anion/cation layers within the first nanometer of the interface. The dynamical response of the EDL to potential steps has a slow component (\textgreater 10 s) and the RTIL structure shows hysteresis during CV scans. We propose a conceptual model that connects nanoscale interfacial structure to the macroscopic measurements. [Preview Abstract] |
Tuesday, March 4, 2014 3:42PM - 3:54PM |
J25.00007: ABSTRACT WITHDRAWN |
Tuesday, March 4, 2014 3:54PM - 4:06PM |
J25.00008: MoS$_{2}$/graphene Composite Paper Electrodes for Na-ion Battery Applications Lamuel David, Gurpreet Singh We study the synthesis, electrochemical and mechanical performance of large area layered freestanding papers composed of acid functionalized few layer molybdenum disulfide (MoS$_{2})$ and reduced graphene oxide (rGO) flakes for use as a self-standing flexible electrode in sodium ion batteries. Synthesis was achieved through vacuum filtration of homogenous dispersions consisting of varying wt. {\%} of exfoliated MoS$_{2}$ flakes in GO in DI water, followed by thermal reduction. The electrochemical behavior of the composite paper was evaluated as counter electrode against pure Na foil in a half-cell configuration. The papers showed good Na cycling ability with charge capacity of approx. 225 mAh.g$^{-1}$ with respect to total weight of the electrode and coulombic efficiency reaching 99{\%}. [Preview Abstract] |
Tuesday, March 4, 2014 4:06PM - 4:18PM |
J25.00009: First Principles Studies for Lithium Intercalation and Diffusion Behaviors in MoS2 treated with the Compressive Sensing Cluster Expansion Chi-Ping Liu, Fei Zhou, Vidvuds Ozolins Molybdenum disulfide (MoS2) is a good candidate electrode material for high capacity energy storage applications, such as lithium ion batteries and supercapacitors. In this work, we investigate lithium intercalation and diffusion kinetics in MoS2 by using first-principles density-functional theory (DFT) calculations. Two different lithium intercalation sites (1-H and 2-T) in MoS2 are found to be stable for lithium intercalation at different van der Waals' (vdW) gap distances. It is found that both thermodynamic and kinetic properties are highly related to the interlayer vdW gap distance, and that the optimal gap distance leads to effective solid-state diffusion in MoS2. Additionally, through the use of compressive sensing, we build accurate cluster expansion models to study the thermodynamic properties of MoS2 at high lithium content by truncating the higher order effective clusters with significant contributions. The results show that compressive sensing cluster expansion is a rigorous and powerful tool for model construction for advanced electrochemical applications in the future. [Preview Abstract] |
Tuesday, March 4, 2014 4:18PM - 4:30PM |
J25.00010: Quasiparticle Energies in Pristine and Oxygen Depleted MoO3 for Pseudocapacitor Applications Keith Ray, Hao Lin, Vidvuds Ozolins, Mark Asta Alpha-MoO3 is a promising electrode material for pseudocapacitors, devices that store electrical energy faradaically, but feature fast reactions/intercalations enabling high power applications [1]. Electrical conductivity and optical properties in alpha-MoO3 are strongly affected by defects, such as oxygen vacancies, which affect the electronic structure. Utilizing self-consistent GW calculations in the quasiparticle picture, along with G0W0 calculations with starting orbitals from HSE06 and DFT$+$U, we calculate the electronic structure of pristine and oxygen depleted alpha-MoO3. We focus on the sensitivity of our results to the calculated description of the localized d-electron states and compare with band gap values determined by measurements on optical properties, electrical conductivity, and photoemission spectroscopy from the literature.\\[4pt] [1] T. Brezesinski, J. Wang, S. H. Tolbert and B. Dunn, Nature Materials 9, 146 (2010) [Preview Abstract] |
Tuesday, March 4, 2014 4:30PM - 4:42PM |
J25.00011: Charge storage in $\beta$-FeSi$_2$ nanoparticle layers Axel Lorke, Jens Theis, Sebastian K\"{u}pper, Robert Bywalez, Hartmut Wiggers We report on the observation of a surprisingly high specific capacitance of $\beta$-FeSi$_2$ nanoparticle layers. Lateral, interdigitated capacitor structures were fabricated on silicon dioxide and covered by FeSi$_2$ particles [1] in the size range 10-30 nm. Compared to the bare electrodes, the nanoparticle-coated samples exhibit a 3-4 orders of magnitude increased capacitance. Time-resolved current-voltage measurements show that for short times (seconds to minutes), the material is capable of storing up to 1 As/g at voltages of around 1 V. The devices are rugged and exhibit long-term stability under ambient conditions. The specific capacitance is the highest for a relative humidity of \~95\%, while for a relative humidity below 40\% the capacitance is almost indistinguishable from the bare electrodes. This strongly suggests that the storage mechanism is not purely geometric and that a -yet unexplored- electrochemical process may be responsible for the observed high specific capacitance. Our findings may also be of technological interest: The devices work without the need of a fluid phase, the charge storing material is earth abundant and cost-effective, and the sample design is easy to fabricate. \\ (1) Robert Bywalez et al., J. Nanopart. Res. 15, 1878 (2013). [Preview Abstract] |
Tuesday, March 4, 2014 4:42PM - 4:54PM |
J25.00012: Simulation of electric double-layer capacitors: evaluation of constant potential method Zhenxing Wang, Brian Laird, Yang Yang, David Olmsted, Mark Asta Atomistic simulations can play an important role in understanding electric double-layer capacitors (EDLCs) at a molecular level. In such simulations, typically the electrode surface is modeled using fixed surface charges, which ignores the charge fluctuation induced by local fluctuations in the electrolyte solution. In this work we evaluate an explicit treatment of charges, namely constant potential method (CPM)\footnote{Reed et al. J. Chem. Phys., \textbf{126}, 084704 (2007)}, in which the electrode charges are dynamically updated to maintain constant electrode potential. We employ a model system with a graphite electrode and a LiClO$_4$/acetonitrile electrolyte, examined as a function of electrode potential differences. Using various molecular and macroscopic properties as metrics, we compare CPM simulations on this system to results using fixed surface charges. Specifically, results for predicted capacity, electric potential gradient and solvent density profile are identical between the two methods; However, ion density profiles and solvation structure yield significantly different results. [Preview Abstract] |
Tuesday, March 4, 2014 4:54PM - 5:06PM |
J25.00013: Improved modeling of electrified interfaces using the effective screening medium method Ikutaro Hamada, Osamu Sugino, Nic{\'e}phore Bonnet, Minoru Otani The effective screening medium (ESM) method has been developed as a way to simulate electrified interfaces within a first principles framework using periodic boundary conditions. Given a slab geometry standing for the interface, the ESM method allows filling the region away from the slab with a dielectric screening medium-- the ESM per se--as a simple way to include electrostatic screening effect of the environment. In the original version of the ESM method, the relative permittivity changes discontinuously from $\epsilon=1$ to $\epsilon > 1$ at the boundary located between the molecular system and the ESM, which causes numerical instability when the electron density of the molecular system touches the boundary. Here we improve upon the description of the screening medium by imposing a smooth transition of the dielectric permittivity between the molecular system and the ESM (smooth ESM), thus precluding numerical instabilities when molecules come in contact with the ESM. Moreover, at short distances, the smooth ESM acts as a repulsive wall, and thus the simulation cell can serve as a natural container for molecules in molecular dynamics simulations. Consequently, the smooth ESM method is a substantial advancement in modeling solid-liquid interfaces under electric bias. [Preview Abstract] |
Tuesday, March 4, 2014 5:06PM - 5:18PM |
J25.00014: Direct Observation of Virtual Electrode Formation Through a Novel Electrolyte-to-Electrode Transition David Siegel, Farid El Gabaly, Norman Bartelt, Kevin McCarty Novel electrochemical solutions to problems in energy storage and transportation can drive renewable energy to become an economically viable alternative to fossil fuels. In many electrochemical systems, the behavior of a device can be fundamentally limited by the surface area of a triple phase boundary, the boundary region where a gas-phase species, electrode, and electrolyte coincide. When the electrode is an ionic insulator the triple phase boundary is typically a one-dimensional boundary with nanometer-scale thickness: ions cannot transport through the electrode, while electrons cannot be transported through the electrolyte. Here we present direct experimental measurements of a novel electrolyte-to-electrode transition with photoemission electron microscopy, and observe that the surface of an ionically conductive, electronically insulative solid oxide electrolyte undergoes a transition into a mixed electron-ion conductor in the vicinity of a metal electrode. Our direct experimental measurements allow us to characterize this system and address the mechanisms of ionic reactions and transport through comparisons with theoretical modeling to provide us with a physical picture of the processes involved. Our results provide insight into one of the mechanisms of ion transport in an electrochemical cell that may be generalizable to other systems. [Preview Abstract] |
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