Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session G45: Focus Session: Polymers in Batteries and Electrochemical Capacitors I |
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Sponsoring Units: DPOLY Chair: Joe Elabd, Texas A&M University Room: 216AB |
Tuesday, March 3, 2015 11:15AM - 11:51AM |
G45.00001: Electrostatic Assembly of Nanomaterials for Hybrid Electrodes and Supercapacitors Invited Speaker: Paula Hammond Electrostatic assembly methods have been used to generate a range of new materials systems of interest for electrochemical energy and storage applications. Over the past several years, it has been demonstrated that carbon nanotubes, metals, metal oxides, polymeric nanomaterials, and biotemplated materials systems can be incorporated into ultrathin films to generate supercapacitors and battery electrodes that illustrate significant energy density and power. The unique ability to control the incorporation of such a broad range of materials at the nanometer length scale allows tailoring of the final properties of these unique composite systems, as well as the capability of creating complex micron-scale to nanoporous morphologies based on the scale of the nanomaterial that is absorbed within the structure, or the conditions of self-assembly. Recently we have expanded these capabilities to achieve new electrodes that are templated atop electrospun polmer fiber scaffolds, in which the polymer can be selectively removed to achieve highly porous materials. Spray-layer-by-layer and filtration methods of functionalized multiwall carbon nanotubes and polyaniline nanofibers enable the generation of electrode systems with unusually high surface. Incorporation of psuedocapacitive nanoparticles can enhance capacitive properties, and other catalytic or metallic nanoparticles can be implemented to enhance electrochemical or catalytic function. [Preview Abstract] |
Tuesday, March 3, 2015 11:51AM - 12:03PM |
G45.00002: High Energy Density and High Temperature Multilayer Capacitor Films for Electric Vehicle Applications Imre Treufeld, Michelle Song, Lei Zhu, Eric Baer, Joe Snyder, Deepak Langhe Multilayer films (MLFs) with high energy density and high temperature capability (\textgreater 120 $^{\circ}$C) have been developed at Case Western Reserve University. Such films offer a potential solution for electric car DC-link capacitors, where high ripple currents and high temperature tolerance are required. The current state-of-the-art capacitors used in electric cars for converting DC to AC use biaxially oriented polypropylene (BOPP), which can only operate at temperatures up to 85 $^{\circ}$C requiring an external cooling system. The polycarbonate (PC)/poly(vinylidene fluoride) (PVDF) MLFs have a higher permittivity compared to that of BOPP (2.3), leading to higher energy density. They have good mechanical stability and reasonably low dielectric losses at 120 $^{\circ}$C. Nonetheless, our preliminary dielectric measurements show that the MLFs exhibit appreciable dielectric losses (20{\%}) at 120 $^{\circ}$C, which would, despite all the other advantages, make them not suitable for practical applications. Our preliminary data showed that dielectric losses of the MLFs at 120 $^{\circ}$C up to 400 MV/m and 1000 Hz originate mostly from impurity ionic conduction. [Preview Abstract] |
Tuesday, March 3, 2015 12:03PM - 12:15PM |
G45.00003: Orientationally Ordered Lamellar Block Copolymer Films for Electrostatic Capacitor Applications Christopher Grabowski, Saumil Samant, Alamgir Karim, Michael Durstock Improving the maximum operating voltage of an electrostatic capacitor requires materials that can better suppress breakdown initiation and/or forestall breakdown propagation. Progress has been made in developing layered architectures through polymer co-extrusion and inorganic nanolaminates, which create tortuous pathways to the applied electric field, resulting in increased breakdown strength. Block copolymer films provide another route to achieve such layered structures, while allowing more control over orientation, domain size, and morphology. We report the dielectric performance of micron-thick linear diblock copolymer films consisting of polystyrene-b-poly-2-vinylpyridine and polystyrene-b-poly methyl methacrylate, focusing on molecular weight ratios that yield lamellar and spherical morphologies. Specialized techniques such as cold-zone soft shear annealing allow for the precise control of lamellae orientation (layering parallel or perpendicular to the applied electric field). Our results indicate dielectric breakdown performance for parallel ordered lamellae is greater than comparable perpendicular lamellae and as-cast films with no induced microphase separation, which we attribute to the presence of interfacial layers that act as barriers to the applied field. [Preview Abstract] |
Tuesday, March 3, 2015 12:15PM - 12:27PM |
G45.00004: Origins of enhanced capacity retention in copolymerized sulfur-based composite cathodes for Li-S batteries Christopher Soles, Vladimir Oleshko, Jenny Kim, Steven Hudson, Kookeon Char, Jared Griebel, Adam Simmonds, Richard Glass, Jeff Pyun Poly(sulfur-random-(1,3-diisopropenylbenzene) (poly(S-r-DIB)) copolymers synthesized via inverse vulcanization form high molecular mass electrochemically active polymers capable of enhanced capacity (1005 mAh/g at 100 cycles) and lifetimes over 500 cycles as cathodes for Li-S batteries. In this presentation we characterize the morphology when the poly(S-r-DIB) copolymers are mixed conductive carbon to form functional Li-S cathodes. Scanning and transmission electron microscopy are used to demonstrate that the use elemental sulfur leads to heterogeneous aggregates of carbon nanoparticles and poor mixing with the sulfur, forming a loosely percolated network of electrically conductive pathways and extended micro- and mesoscale porosity. The poly(S-r-DIB) copolymers tend to mix more intimately with the carbon nanoparticles because of a stronger cohesion between the components. This increases the compositional homogeneity, increases the contact between the electrochemically active components and improves the physico-mechanical stability of the cathode which leads to increased capacity and enhanced cycle life in a full battery. We also introduce a new Li ion microscopy technique as a tool for characterizing battery materials. [Preview Abstract] |
Tuesday, March 3, 2015 12:27PM - 12:39PM |
G45.00005: Effect of Molecular Weight on Mechanical and Electrochemical Performance of All Solid-State Polymer Electrolyte Membranes Ruixuan He, Daniel Ward, Mauricio Echeverri, Thein Kyu Guided by ternary phase diagrams of polyethylene glycol diacrylate (PEGDA), succinonitrile plasticizer, and LiTFSI salt, completely amorphous solid-state transparent polymer electrolyte membranes (ss-PEM) were fabricated by UV irradiation in the isotropic melt state. Effects of PEGDA molecular weight (700 vs 6000 g/mol) on ss-PEM performance were investigated. These amorphous PEMs have superionic room temperature ionic conductivity of $\sim$10$^{-3}$ S/cm, whereby PEGDA6000-PEM outperforms its PEGDA700 counterpart, which may be ascribed to lower crosslinking density and greater segmental mobility. The longer chain between crosslinked points of PEGDA6000-PEM is responsible for greater extensibility of $\sim$80\% versus $\sim$7\% of PEGDA700-PEM. Besides, both PEMs exhibited thermal stability up to 120 $^{\circ}$C and electrochemical stability versus Li$^{+}$/Li up to 4.7V. LiFePO$_{4}$/PEM/Li and Li$_{4}$Ti$_{5}$O$_{12}$ /PEM/Li half-cells exhibited stable cyclic behavior up to 50 cycles tested with a capacity of $\sim$140mAh/g, suggesting that LiFePO$_{4}$/PEM/Li$_{4}$Ti$_{5}$O$_{12}$ may be a promising full-cell for all solid-state lithium battery. [Preview Abstract] |
Tuesday, March 3, 2015 12:39PM - 12:51PM |
G45.00006: Stacked Polymer nanofiber array for high-performance supercapacitors Shiren Wang, Jenny Qiu The vertically aligned polyaniline (PANI) nanowires arrays and monolayer graphene sheets were layer-by-layered deposited to specific substrate for tailored structures. Driven by external voltage, aniline molecules and graphene oxide were alternatively assembled for hierarchical porous three-dimensional nanostructures while graphene oxide was in-situ reduced to graphene during the assembly process. As-produced stacked arrays were used as the electrodes of an ultra-capacitor, and an unusual electrochemical behavior was discovered. The capacitance increases as the stack of nanowire arrays increases, resulting in high energy density and high power density at same time. Further analysis found that the distinctive electrochemical behavior originates from the electrode/electrolyte interactions and the dependence on the diffusion and charge transferring process. The specific energy density was as high as 137 Wh/Kg while power density is in excess of 2000 W/Kg. This work pointed a simple pathway to tailor polymer structure and electrochemistry for robust design of high-performance ultra-capacitor at a limited lateral size. [Preview Abstract] |
Tuesday, March 3, 2015 12:51PM - 1:03PM |
G45.00007: Sprayable, Paintable Layer-by-Layer Polyaniline Nanofiber/Graphene Electrodes for Electrochemical Energy Storage Se Ra Kwon, Ju-Won Jeon, Jodie Lutkenhaus Sprayable batteries are growing in interest for applications in structural energy storage and power or flexible power. Spray-assisted layer-by-layer (LbL) assembly, in which complementary species are alternately sprayed onto a surface, is particularly amenable toward this application. Here, we report on the fabrication of composite films containing polyaniline nanofibers (PANI NF) and graphene oxide (GO) sheets fabricated via spray-assisted LbL assembly. The resulting films are electrochemical reduced to yield PANI NF/electrochemically reduced graphene (ERGO) electrodes for use as a cathode in non-aqueous energy storage systems. Through the spray-assisted LbL process, the hybrid electrodes could be fabricated 74 times faster than competing dip-assisted LbL assembly. The resulting electrodes are highly porous (0.72 void fraction), and are comprised of 67 wt{\%} PANI NF and 33 wt{\%} ERGO. The sprayed electrodes showed better rate capability, higher specific power, as well as more stable cycle life than dip-assisted LbL electrodes. It is shown here that the spray-assisted LbL approach is well-suited towards the fabrication of paintable electrodes containing polyaniline nanofibers and electrochemically reduced graphene oxide sheets. [Preview Abstract] |
Tuesday, March 3, 2015 1:03PM - 1:15PM |
G45.00008: Superionic solid-state polymer electrolyte membrane for high temperature applications Thein Kyu, Ruixuan He, Jinwei Cao Completely amorphous, flexible, solid-state polymer electrolyte membranes (ss-PEM) consisted of polyethylene glycol diacrylate /succinonitrile plasticizer (SCN)/lithium trifluorosulfonyl imide were fabricated via UV polymerization. The room temperature ionic conductivity of our ss-PEM is extremely high (i.e., ~ 10$^{-3}$S/cm), which is already in the superionic conductor range of inorganic and/or liquid electrolyte counterparts. Of particular interest is that our ss-PEM is thermally stable up to 140$^{\circ}$C, which is superior to the liquid electrolyte counterpart that degrades above 80$^{\circ}$C. The ss-PEM exhibits cyclic stability in both LiFePO$_{4}$/Li and Li$_{4}$Ti$_{5}$O$_{12}$ /Li half-cells up to 50 cycles tested. The trend of conductivity enhancement with temperature is reproducible in the repeated cycles, showing melting transitions of the SCN plastic crystals. In the compositions close to the solid (SCN plastic crystal)-liquid coexistence line, polymerization-induced crystallization occurs during photo-curing. The effect of solid-liquid segregation on ionic conductivity behavior is discussed. [Preview Abstract] |
Tuesday, March 3, 2015 1:15PM - 1:27PM |
G45.00009: Spatial position control of nanofeatures assisted by nanoporous templates fabricated by block copolymer based lithography Dong Hyun Lee, Dong-Eun Lee Herein, we demonstrated a unique method to control spatial arrangement of nanostructures by using topographically patterned substrates. The thin films of block copolymers (BCPs) were firstly prepared on a thin layer of poly(vinyl alcohol) (PVA). Then to induce ordering of the BCPs, the thin films were solvent-annealed in organic solvent vapors. The BCP thin films were then utilized as a mask to fabricate ordered PVA nanopores by reactive ion etching. Different types of BCP micelles were sequentially spin-coated on the nanoporous PVA film. Interestingly, the BCP micelles having hydrophobic surface could immediately be self-assembled due to synergetic effects of surface energy difference and height contrast of the PVA film during evaporation of a suspension solvent. In addition, by combining topographically patterned substrates, long-rage lateral ordering of BCP micelles depending on inter-distance and diameter of the PVA nanopores were effectively achieved over whole surface area. [Preview Abstract] |
Tuesday, March 3, 2015 1:27PM - 1:39PM |
G45.00010: Electrochemical Stability of Model Polymer Electrolyte/Electrode Interfaces Daniel Hallinan, Guang Yang Polymer electrolytes are promising materials for high energy density rechargeable batteries. However, typical polymer electrolytes are not electrochemically stable at the charging voltage of advanced positive electrode materials. Although not yet reported in literature, decomposition is expected to adversely affect the performance and lifetime of polymer-electrolyte-based batteries. In an attempt to better understand polymer electrolyte oxidation and design stable polymer electrolyte/positive electrode interfaces, we are studying electron transfer across model interfaces comprising gold nanoparticles and organic protecting ligands assembled into monolayer films. Gold nanoparticles provide large interfacial surface area yielding a measurable electrochemical signal. They are inert and hence non-reactive with most polymer electrolytes and lithium salts. The surface can be easily modified with ligands of different chemistry and molecular weight. In our study, poly(ethylene oxide) (PEO) will serve as the polymer electrolyte and lithium bis(trifluoromethanesulfonyl) imide salt (LiTFSI) will be the lithium salt. The effect of ligand type and molecular weight on both optical and electrical properties of the gold nanoparticle film will be presented. Finally, the electrochemical stability of the electrode/electrolyte interface and its dependence on interfacial properties will be presented. [Preview Abstract] |
Tuesday, March 3, 2015 1:39PM - 1:51PM |
G45.00011: Determination of Lithium Ion Distributions in Nanostructured Block Polymer Electrolyte Thin Films by XPS Depth Profiling Ming Luo, Jonathan Gilbert, Cameron Shelton, Michael Rubner, Robert Cohen, Thomas Epps We present the first experimental, quantitative determination of lithium salt distributions in nanostructured block polymer electrolyte thin films. High resolution C60+ depth profiling X-ray photoelectron spectroscopy (XPS) was employed to resolve the ion distribution in a lamellar forming block polymer electrolyte thin film, which is considered challenging by conventional scattering or electron microscopy techniques. This experimental technique is applicable to investigations of nanoscale distributions of molecules in a myriad of nanostructured polymer thin film systems. Our results have important implications for understanding ion transport in nanostructured polymer systems and provide crucial insights for the future design and optimization of block polymer structures for high efficiency energy storage devices. [Preview Abstract] |
Tuesday, March 3, 2015 1:51PM - 2:03PM |
G45.00012: High Performance Electroactive Polymer Actuators Based on Sulfonated Block Copolymers Comprising Ionic Liquids Onnuri Kim, Moon Jeong Park Electroactive polymer (EAP) actuators that show reversible deformation under external electric stimulus have attracted great attention toward a range of biomimetic applications such as microsensors and artificial muscles. Key challenges to advance the technologies can be placed on the achievement of fast response time, low driving voltage, and durable operation in air. In present study, we are motivated to solve these issues by employing self-assembled block copolymers containing ionic liquids (ILs) as polymer layers in the actuator based on knowledge of factors affecting electromechanical properties of actuators. By controlling the block architecture and molecular weight of block copolymers, bending strain and durability were controlled in a straightforward manner. It has also been revealed that the type of IL makes impact on the EAP actuator performance by determining ion migration dynamics. Our actuators demonstrated large bending strains (up to 4\%) under low voltages of 1-3V, which far exceeds the best performance of other EAP actuators reported in the literature. To underpin the molecular-level understanding of actuation mechanisms underlying the improved performance, we carried out in situ spectroscopy and in situ scattering experiments under actuation. [Preview Abstract] |
Tuesday, March 3, 2015 2:03PM - 2:15PM |
G45.00013: Effect of Mobile Ions on the Electric Field Needed to Orient Charged Diblock Copolymer Thin Films Ashkan Dehghan, Michael Schick, An-Chang Shi We examine the behaviour of lamellar phases of charged, diblock copolymer, thin films with mobile counter-ions in the presence of an electric field. We employ self-consistent field theory, and focus on the aligning effect of the electric field on the lamellae. Of particular interest are the effects of the mobile ions on the critical field, which is the value of the field required to reorient the lamellae from the parallel configuration favoured by the surface interaction to the perpendicular orientation favoured by the electric field. We find that the critical field depends strongly on the location of the mobile ions within the system. In the case in which mobile ions are confined such that each charged lamellae is electrically neutral, the presence of ions lowers the critical electric field. However, if ions are free to locate anywhere within the system, so that only the system as a whole is electrically neutral, then the presence of ions can increase the critical electric field. The presence of ions in the system introduces a new mixed phase, perpendicular in the bulk, parallel at the surfaces, in addition to those reported previously. [Preview Abstract] |
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