Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session Y15: Polymers and Polymer Composites for Energy Storage and Conversion Applications IFocus
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Sponsoring Units: DPOLY Chair: Pierre Kawak, University of South Florida Room: Room 207 |
Friday, March 10, 2023 8:00AM - 8:36AM |
Y15.00001: Hope for Higher Ion Velocities in Polymer Electrolytes Invited Speaker: Nitash P Balsara The need for creating safe electrolytes for lithium batteries is significant given the continued safety problems associated with current lithium-ion batteries. Nonflammable polymer electrolytes, mixtures of polymers and salt, offer a possible solution but the rate of lithium ion transport is too low for practical applications. In this talk, I will discuss some of the fundamental factors that limit ion transport in polymers. The performance of electrolytes depends on the current of the working ion under an applied electric potential. Since the current is proportional to the product of the concentration and ion velocity, the velocity of the working ion is of paramount importance. We discuss approaches for predicting ion velocities based on Newman's concentrated solution theory. The importance of the continuity equation in the presence of ionic current is discussed. We test our predictions on a standard polymer electrolyte based on poly(ethylene oxide) (PEO). To obtain a mechanically robust solid electrolyte, we use PEO-containing block copolymers wherein the other block is glassy (and rigid) polystyrene. Ion transport through these systems can also be described by concentrated solution theory. We conclude by describing our efforts to develop new polymers that exhibit higher ion velocities than PEO. |
Friday, March 10, 2023 8:36AM - 8:48AM |
Y15.00002: Tuning Ion and Polymer Dynamics of Single-Ion Polymer Electrolytes by Crystalline Plasticizers or Cross-linking Nanoparticles U Hyeok Choi, Seonho Kim, Puji L Handayani, Su Sung Yun, Jaekyun Kim Dielectric relaxation spectroscopy (DRS) and oscillatory shear are used to investigate ion dynamics of a series of poly(lithium acrylate) (PLiA)-based single-Li+ conducting polymer electrolytes, where PLiA is either copolymerized with poly(ethylene glycol) methyl ether methacrylate in N-methylacetamide for non-aqueous polymer electrolytes or cross-linked with vinyl silica nanoparticles in water for aqueous polymer electrolytes. To deduce the mechanism of ion transport in these single-ion conducting gel polymer electrolytes (SGPEs), the Macdonald and Onsager models are used to separately determine the number density of conducting ions and their mobility and to understand mobile isolated dipole motions, from analysis of electrode polarization and dielectric constant in DRS. The electrochemical performance is also explored in the SGPE assembled with electrodes, as supercapacitors or lithium-metal batteries. These fundamental results can provide insights into the design of fast Li+ conducting solid-state polymer electrolytes for energy storage devices. |
Friday, March 10, 2023 8:48AM - 9:00AM Author not Attending |
Y15.00003: Tracking salt concentration gradients and block copolymer electrolyte phase transitions using in situ SAXS during cell polarization Emily Abdo Block copolymer (BCP) electrolytes with lithium salt offer promise as next generation electrolytes for Li-ion batteries. Unlike conventional liquid electrolytes, BCPs are not plagued by flammability issues. Furthermore, by incorporating a mechanically-rigid block, they can suppress deleterious dendrite formation and enable the use of higher-energy density lithium metal anodes. Here we study polystyrene-block-poly(ethylene oxide) (SEO) mixed with lithium bis-(trifluoromethanesulfonyl)imide (LiTFSI) salt in lithium-lithium symmetric cells under constant applied current. Under equilibrium conditions, this SEO system exhibits hexagonally packed cylindrical (HEX) morphology but can display gyroid (GYR) morphology at lower salt concentrations. By using in-situ SAXS during cell polarization, we measure the formation of salt concentration gradients within the cell and simultaneously track the morphological changes as a function of position and time. While recent work found that a transition from body-centered cubic spherical (BCC) morphology to HEX in a higher molecular weight SEO was inaccessible and led to premature cell failure, here we detect the phase transition from HEX to GYR at the salt depleted electrode. Moreover, the relative prominence of HEX and GYR populations varies strongly with orientation (parallel or perpendicular to ion transport). Thus we see that certain phase transitions are accessible and elucidate an interplay between BCP grain orientation and electrochemical cell properties. |
Friday, March 10, 2023 9:00AM - 9:12AM |
Y15.00004: Diffusive Charge Transport in High-Valency Redox-Active Polymer Solutions Liliana Bello Fernandez, Charles E Sing Redox-active polymers (RAPs) are a promising material for redox-flow batteries which are durable, scalable, and can quickly charge and discharge. However, redox material crossover can diminish capacity and lifetime of redox flow batteries. A strategy to mitigate this crossover uses porous membranes to separate RAP-based anolytes and catholytes by size exclusion. The performance of these batteries is related to charge transport mechanisms in these RAP solutions leading to an interest in understanding its fundamental physics. |
Friday, March 10, 2023 9:12AM - 9:24AM |
Y15.00005: Revealing Local Structure and Dynamics in Li-salt Electrolytes using Dielectric Relaxation Spectroscopy Benjamin A Paren, Graham A Leverick, Benjamin D Burke, Jeffrey Lopez, Yang Shao-Horn Understanding the interplay between local structure and transport is critical for establishing design rules in polymer electrolytes. In this work, a set of Li-salt in liquid electrolytes is studied as a model system to examine correlations between several electrolyte properties, including conductivity, dielectric relaxation time and strength, ionicity, and viscosity. These properties were evaluated by changing ion concentration, solvent type, and anion type. Dielectric relaxation spectroscopy was used, in combination with other experimental techniques, to identify the relaxation processes associated with the different ion-solvent complexes. The dielectric relaxation time of the solvent-ion complexes, is independent of ion content at low salt concentrations, when solvent separated ion pairs dominate. At high ion concentrations, molar conductivity depends more strongly on this relaxation time as solvent dielectric constant is reduced, which we suspect is due to variation in shielding between ion pairs and aggregates. In contrast, there is no clear change in the dependence of molar conductivity on dielectric relaxation time with changing anion. This study provides insight into different local structures and dynamic processes that contribute to conductivity. While Li-salts in liquid solvents are presented here as a model system, the findings discussed in this work could be applied to polymeric systems, laying a foundation for the design of new polymer electrolytes. |
Friday, March 10, 2023 9:24AM - 9:36AM |
Y15.00006: Enhanced dielectric strength and capacitive energy density in ultrathin glassy polymer films Maninderjeet Singh, Alamgir Karim, Jack F Douglas Ultrathin polymer films present unique opportunities to understand the physics and properties of polymers at the nanoscale when the film thicknesses become comparable to the polymer dimensions. In this work, we demonstrate that ultrathin glassy polymer films (~100 nm) show an order of magnitude higher dielectric strength (EBD) and capacitive energy density (Umax ∝ EBD2) of ~27 J/cm3 as compared to the bulk polymer films when used as dielectric capacitors. We believe that the enhancement of the dielectric strength and capacitive energy density is due to the tighter chain packing of polymers in ultrathin films. We test the density of thin polymer films by optical measurements and observe that the ultrathin films show higher densities and thus lower free volume as compared to their bulk counterparts, which might be a governing factor for the enhancement of the dielectric strength. Moreover, the ultrathin films of polymers having sub-room temperature glass transition don’t show ultra-high dielectric strength and capacitive energy density, which might be due to the presence of excess free volume in these polymer films that act as defect sites for breakdown. The high dielectric strength of ultrathin polymer films might help in increasing the understanding of polymer behavior in ultrathin films. |
Friday, March 10, 2023 9:36AM - 9:48AM |
Y15.00007: Ultra-high Capacitive Energy Density in Heterostructure of Polymer and Stratified 2D Layered Nanofiller Composites Nihar R Pradhan, Priyanka R Das, Maninderjeet Singh, Pabitra Sammanta, Roshanak Nejat, Banarji Behera, Brian T Shook, Qiqi Zhang, Qilin Dai, Avijit Pramanik, Paresh Ray, Dharmaraj Raghavan, Jerzy Leszczysnki, Alamgir Karim Developing a thin polymer based dielectric film with improved dielectric constant and breakdown voltage is one of the emerging fields of interest to create next generation high power density energy-storage device. Here, we willresent remarkably enhanced dielectric constant and energy density of a polymer nanocomposite, PVDF with incorporated an exfoliated layered 2D dielectric crystals Mica or h-BN in a stratified heterostructure stacking geometry. The dielectric constant of this structure shows ~100% enhancement over the pristine PVDF based polymer, achieved using an ultra-low loading (~1 vol%) of 2D Mica nanofillers. A dramatic enhancement of breakdown voltage is also measured in these 2D-Mica or h-BN interfaced stratified heterostructure assembly (1000-1200 V/µm) compared to the pristine polymer heterostructure film (558-700 V/µm). We observed an energy density as high as 75 J/cm3 from the 2D-Mica interfaced polymer heterostructure construct, which is the highest among the observed energy density of the polymer-nanocomposite based dielectrics. Our computational study using density function theory supports our experimental finding. This work will provide to achieve thin film based large-scale fabrication of high-density energy storage devices using low-cost polymer nanocomposites for myriads of potential applications for flexible electronics. |
Friday, March 10, 2023 9:48AM - 10:00AM |
Y15.00008: Zwitterionic Polymers for Capacitance Applications Dorian Bruch, Zhen-Gang Wang With the advent of sustainable and renewable energy technologies, there is an ever-growing demand to improve energy storage devices such as supercapacitors. One such way to improve supercapacitors is to increase its capacitance with high-dielectric mediums, although most materials rarely exceed the dielectric constant of water (ε = 80). Zwitterionic polymers, however, are promising materials recently reported experimentally to have dielectric constants on the order of hundreds. Using a simple incompressible discrete gaussian-chain mean-field theory with electrostatic interactions, we demonstrate that zwitterionic polymers exhibit dielectric constants on the order of hundreds. We also predict nonmonotonicity in dielectric constant as a function of chain length, leading to an optimal dielectric constant. Additionally, we show that the zwitterionic polymer screens electrostatic forces on short length scales near surfaces but acts as a dielectric medium in the bulk, and we characterize the nature of this screening. Lastly, we find that zwitterionic polymer capacitors display improvements over traditional electric double-layer capacitors. |
Friday, March 10, 2023 10:00AM - 10:12AM |
Y15.00009: Hairy Nanoparticles Improve Cycling Stability of a Solid-State Polymer Electrolyte Vera Bocharova, Chelsea Chen, Seung Pyo Jeong, Zhengping Zhou, Robert Sacci, Catalin Gainaru, Md Anisur Rahman, Ritu Sahore, Xiao-Guang Sun, Pengfei Cao, Andrew Westover The development of solid electrolytes that prevent dendrite growth while providing the desired level of conductivity is essential for improving the cycling stability of solid-state Li metal batteries. In this paper, we report the synthesis of single Li-ion conducting hairy nanoparticle (NP) materials that improved the cycling stability of a model solid polymer electrolyte without significant reduction in its conductivity. Several characterization techniques including broadband dielectric spectroscopy (BDS), differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), shear rheology are used to study the properties of polymer composites with added hairy NPs. It is found that the addition of hairy NPs stabilizes the Li/electrolyte interface and improves both the Li+ transport number and the mechanical properties of bulk composites, all of which contribute to homogenous Li plating and stripping. Based on the discovered ability of hairy NPs to influence bulk and interfacial properties of electrolytes, their use as additives is expected to be equally effective in reducing dendrite formation in diverse electrolytes. |
Friday, March 10, 2023 10:12AM - 10:24AM |
Y15.00010: Impact of dispersion characteristics on ionomer thin film properties Ahmet Kusoglu, Ashley Bird Ion-conducting polymers (ionomers) are an important component in the heterogenous electrodes (catalyst layers) of energy conversion devices such as fuel cells and electrolyzers. Ionomer facilitates mass transport to and from the catalyst sites in the electrodes, which are fabricated through solution-based processing methods. Despite empirical evidence on the role of solvents and processing on device performance, their effect on ionomer structure-property relationships remains unexplored. This talk focuses on the impact of dispersion’s solvent composition and processing on spin-cast ionomer thin films (<100 nm), which are used as model systems for catalyst ionomers. By characterizing the ionomer both in the dispersion state and after casting into a film on various supports, insights are gained into the factors controlling the structure-property changes in ionomer thin films. Dispersion characteristics observed by pH and x-ray scattering correlated to the changes in the thin film’s structure probed via in situ grazing-incidence x-ray scattering (GIXS), and hydration properties. These results provide insight into the phenomena governing ionomer dispersion structure and the resulting film properties. |
Friday, March 10, 2023 10:24AM - 10:36AM |
Y15.00011: Study of the structure and segmental dynamics of solid-polymer-based composite cathode Chelsea Chen, Charles Soulen, Mary K Burdette-Trofimov, Xiaomin Tang, Changhao Liu, Luke Heroux, Mathieu Doucet, Madhusudan Tyagi, Gabriel Veith This work examines the structure and segmental dynamics of a model polymer electrolyte in a polymer-based composite cathode consisting of LiFePO4 (LFP), carbon and poly(ethylene oxide) (PEO) with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). By using small angle neutron scattering (SANS) and quasi-elastic neutron scattering (QENS), it is discovered that that a strong interaction between LFP and PEO chains causes the segmental mobility of PEO to decrease by 70% and the Li+ mobility in PEO/LiTFSI in the composite cathode is only 30% of the bulk electrolyte. This suggests a key bottleneck that limits the rate performance of polymer-based solid-state batteries originates from the sluggish ion transport in the polymer electrolyte confined in the cathode. More future effort needs to focus on redesigning the polymer cathode. |
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