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 Z15: Polymers and Polymer Composites for Energy Storage and Conversion Applications II |
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Sponsoring Units: DPOLY Chair: Maninderjeet Singh, University of Houston Room: Room 207 |
Friday, March 10, 2023 11:30AM - 11:42AM |
Z15.00001: Anion Conduction and Water Percolation Effects in Polynorbornene-based Thin Film Membranes Shrayesh Patel, Zhongyang Wang, Ge Sun, Paul A Kohl, Juan J De Pablo, Paul F Nealey Anion exchange membranes (AEMs) are at the heart of many electrochemical driven processes such as fuel cells, water electrolysers, reverse electrodialysis, and redox flow batteries. It requires a fundamental understanding of ion transport in AEMs at different hydration states to efficiently operate these systems with long term durability. To allow for better understanding, combining experimental characterizations with targeted simulations reveals new insights on the interplay of water and ion transport in hydrated AEMs. Here, we have synthesized and fabricated polynorbornene-based anion exchange thin films as our model polymers due to their high alkaline stabilities and ionic conductivities via vapor infiltration reactions (VIRs). We customize an in situ ellipsometer to understand thin film expansion at different hydration levels and water uptakes of AEMs has been measured by dynamic water sorption. We investigate bromide ion (Br-) transport by measuring thin film electrochemical impedance as a function of relative humidity and temperature. Br- conductivities show Arrhenius behaviors and activation energy has been extracted as a function of relative humidity. By combining experimental characterizations, percolation theory, and atomistic molecular dynamics simulations, we quantitatively identify two transport regimes (site hopping mechanism and vehicular mechanism) from low to high relative humidity. |
Friday, March 10, 2023 11:42AM - 11:54AM |
Z15.00002: Characterizing Ion Transport in Poly(Pentyl Malonate) Electrolytes Zach Hoffman, Jaeyong Lee, Vivaan Patel, Nitash P Balsara For decades poly(ethylene oxide) (PEO) has been the leading homopolymer for lithium-ion battery polymer electrolytes. The high conductivity of PEO is demonstrative of its superiority; however PEO also has a large range of applied currents under which it can stably perform. Recently, poly(pentyl malonate) (PPM) has been identified as a homopolymer with ion transport properties comparable to PEO along with stable performance under larger applied currents than that of PEO. This study presents the full electrochemical characterization of electrolytes comprised of PPM and LiTFSI salt across a range of salt concentrations to quantify all necessary parameters to describe ion transport in these electrolytes. With these transport parameters, concentrated solution theory can be used to predict lithium salt concentration gradients within the electrolyte under DC polarization along with the theoretical limiting current with which we can compare the measured values. This full characterization provides a deeper understanding of ion transport and the performance limits of PPM electrolytes. |
Friday, March 10, 2023 11:54AM - 12:06PM |
Z15.00003: Molecular Dynamics Simulations of Structure and Ion Transport in Polymeric Zwitterionic Electrolytes Mizuki Kamata, Douglas Grzetic, Kris T Delaney, Amalie L Frischknecht, Glenn H Fredrickson Polymer electrolytes are attracting attention due to their ability to improve the safety and durability of commercial Li ion batteries traditionally consisting of liquid electrolytes; however, they exhibit a lower Li ion conductivity. Recent studies demonstrated that a class of polyzwitterions with LiTFSI as the added lithium salt improves low temperature conductivity but the mechanism of the fast Li transport in polyzwitterion systems is not yet understood. We built model systems of polyzwitterions and studied the Li ion movement inside the system conducting all-atom molecular dynamics simulations. We discuss the influence of the interaction between Li and anionic moieties in the polyzwitterions and the ordered zwitterionic structure at the atomic level. |
Friday, March 10, 2023 12:06PM - 12:18PM |
Z15.00004: Relationship between Ion Transport and Phase Behavior in Acetal-Based Polymer Blend Electrolytes Studied by Electrochemical Characterization and Neutron Scattering Jaeyong Lee, Neel J Shah, Geoffrey W Coates, Nitash P Balsara We have studied ion transport in electrolytes created by blending two different polymers and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The polymers covered in this study are polyethylene oxide (PEO), poly(1,3,6-trioxocane) (P(2EO-MO)), and poly(1,3-dioxolane) (P(EO-MO)). Ion transport is quantified by the product κρ+ which is defined as the efficacy of the electrolytes, where κ is conductivity and ρ+ is the current fraction determined by the Bruce-Vincent method. Polymer blends can be either one-phase or macrophase-separated. We used small angle neutron scattering (SANS) to distinguish between these two possibilities. The random phase approximation (RPA) was used to interpret SANS data from one-phase blends. The effect of added salt on polymer blend thermodynamics is quantified by an effective Flory-Huggins interaction parameter. All polymer blends were one-phase in the absence of salt. Adding salt in small concentrations results in macrophase separation in all cases. One-phase systems were observed in the PEO/P(EO-MO)/LiTFSI blends at high salt concentrations. In most of the polymer blend electrolytes, the measured κρ+ was either lower than or comparable to that of the homopolymer electrolytes. An exception to this was one-phase PEO/P(EO-MO)/LiTFSI blends electrolytes at high salt concentrations. |
Friday, March 10, 2023 12:18PM - 12:30PM |
Z15.00005: Uncovering New Ionomer Membrane Morphology Features with Resonant X-Ray Scattering Gregory Su, Sintu Rongpipi, Ahmet Kusoglu, Guillaume Freychet, Ashley Bird Ion-conducting polymer, or ionomer, membranes play a key role as the ion-conducting electrolyte in electrochemical devices, including fuel cells and electrolyzers. Perfluorinated sulfonic acid (PFSA) ionomers are the most common, and they are cast into membranes and thin films from alcohol-rich dispersions. We examine the connections between dispersion and membrane properties. Controlling the phase separated morphology of the ionomer and understanding its relationship to transport properties is crucial for improving ion transport and device performance. It is challenging for hard x-ray scattering to resolve all the morphological details in chemically heterogeneous ionomers. We use tender resonant x-ray scattering (TReXS) near the sulfur K-edge to improve scattering contrast and enhance chemical specificity to the sulfonate groups in PFSA ionomers. We find that TReXS reveals unique energy-dependent morphological features not apparent in hard x-ray scattering that depend on dispersion composition and ionomer chemistry. These structure-property relationships can be used to guide design of next-generation ionomers for energy applications. Furthermore, this work highlights TReXS as an emerging technique for structural characterization of ionomers and chemically heterogeneous polymers in general. |
Friday, March 10, 2023 12:30PM - 12:42PM |
Z15.00006: Understanding the Role of Water Molecules and Ion Transport Mechanisms in Anion Exchange Membranes Ge Sun, Zhongyang Wang, Abhishek K Sharma, Shrayesh Patel, Paul F Nealey, Juan J De Pablo Understanding the ion transport mechanisms of anion exchange membranes (AEMs) is crucial for the design of efficient polymer electrolytes for fuel cells and other electrochemical technologies. A key challenge in understanding the ion transport properties of AEMs is the lack of a methodology that combines macroscopic experimental characterizations with simulation results to probe ion transport mechanisms at different hydration states from a molecular level. Here we develop a methodology to investigate site hopping and vehicular transport mechanisms using anion exchange thin films, interdigitated electrodes, and atomistic molecular dynamics (MD) simulations. Bromide ion conductivities in polynorbornene-based thin films are measured as a function of temperature and relative humidity using electrochemical impedance spectroscopy. Bromide ion transport shows Arrhenius behaviors, and activation energy (Ea) is used for the first time as an indicator for detecting the transition of site hopping and vehicular transport mechanisms. Percolation theory is examined and enriched by combining experimental results and MD simulations. We quantitatively demonstrate that the transition of site hopping and vehicular mechanisms is aided by better solvation environments of anions and more percolated water pathways at 55% RH. The change in conductivity observed by both experiments and simulations could be attributed to the microstructural change in the robustness of percolation. These results have important implications for the design of AEMs as efficient ion-conducting membranes. |
Friday, March 10, 2023 12:42PM - 12:54PM |
Z15.00007: Zwitterionic Polymer Promotion of Selective Ion Transport in Ionic Liquid Electrolytes Meron Y. Tadesse, Zidan Zhang, Nico Marioni, Everett S Zofchak, Venkatraghavan Ganesan Recent experimental results have demonstrated that zwitterionic (ZI) gel electrolytes comprising lithium salt and ionic liquid are useful in the advancement of decoupling mechanical stiffness and ionic conductivity. However, the underlying mechanism of such decoupling between the structural and dynamic properties of the ZI gel electrolytes remains unsolved. In this work, we perform a systematic investigation to understand the impact of the ZI/ Lithium molar ratio on the structural and dynamic properties using atomistic molecular dynamics simulations. Our model system is comprised of ZI poly (2-methacryloyloxyethyl phosphorylcholine) (pMPC) loaded with 1M LiTFSI/N-butyl-N-methylpyrrolidinium (BMP) TFSI ionic liquid electrolyte. Our structural analyses show strong lithium ion interaction with the anionic portion of the polymer consistent with the physical network characteristic observed in the experimental results. We also present ion coordination statistics and ion pair lifetimes results to rationalize and identify the mechanistic origins of the dynamic properties of the ZI gel electrolytes. |
Friday, March 10, 2023 12:54PM - 1:06PM |
Z15.00008: Effect of Hydrodynamic Interactions and Flow on Charge Transport in Redox Active Polymer Solutions Dejuante Walker, Charles E Sing Redox-active polymers (RAPs) are a subclass of polyelectrolytes that can store charge and undergo redox self-exchange reactions. They are of great interest in the field of redox flow batteries due to their ability to quickly charge and discharge, their chemical modularity, and their molecular size. However, the numerous physicochemical attributes of RAPs are an opportunity to design at the molecular level for efficient charge transport, which require a fundamental understanding of charge transport mechanisms for redox flow batteries. This work has improved previous models by incorporating both hydrodynamic interactions (HI) and out-of-equilibrium dynamics to resemble flow battery conditions more closely. This has been achieved using the conformationally averaged Brownian Dynamics simulation method paired with Monte Carlo. The model is used to show that HI is an important feature when charge hopping is not the major mechanism for charge displacement. Furthermore, it has been shown that the flow conditions may result in either enhanced or decreased transport – depending on the fraction of charges present on the RAP chain. This model is a first of its kind in that both charge transport and flow is simultaneously modeled in an RAP solution. |
Friday, March 10, 2023 1:06PM - 1:18PM |
Z15.00009: Comparative morphological and dielectric properties measurements of homopolymer and block copolymer grafted BaTiO3 nanoparticles Ikeoluwa Apata, Maninderjeet Singh, Bhausaheb Tawade, Alamgir Karim, Dharmaraj Raghavan The use of one component system of block polymer grafted nanoparticles is expected to prevent nanoparticle aggregation, result in uniform dispersion, and reduce the dielectric mismatch between the nanoparticle and polymer matrix and improve the overall dielectric performance of nanocomposites. In this study, surface-initiated atomic transfer radical polymerization (Si-ATRP) was used to synthesize core-shell barium titanate-poly(methyl methacrylate) (BaTiO3-PMMA), barium titanate-polystyrene (BaTiO3-PS) polymer grafted nanoparticle and ARGET-ATRP was used to synthesized block copolymer grafted nanoparticles (BaTiO3-PS-b-PMMA and BaTiO3-PMMA-b-PS). The molecular weights and dispersities of synthesized homopolymer and BCP nanoparticles were in the range of 31000 g/ml to 150000 g/mol and 1.2 to 1.8, respectively, indicating controlled growth of the polymer on the BaTiO3 surface. The dielectric study of homopolymer BT-PMMA exhibited improved dielectric constant (3.7 to 9.9), low dielectric loss (< 0.05) with a high breakdown strength (200 to 347 V/µm), resulting in high energy densities (0.82 to 5.2 J/cm3) compared to pure polymer system. We are currently evaluating the dielectric performance of BT-BCP and results will be used to compare the dielectric performance of BaTiO3-BCP to that of BaTiO3-homopolymers single component system. The matrix-free single-component system can have far-reaching applications in the electronics industry. |
Friday, March 10, 2023 1:18PM - 1:30PM |
Z15.00010: Mechanisms of Dielectric and Electromechanical Enhancements in PVDF-Based Tetrapolymers Jerzy Bernholc, Hancheng Qin, Xin Chen, Bing Zhang, Wenchang Lu, Qiming Zhang We describe simulations of electric-field-induced structural transformations in P(VDF-TrFE) polymers with small admixtures of chlorofluoroethylene (CFE) and fluorinated alkyne (FA) monomers. At low concentrations, FA monomers provide pivot points that facilitate transformations of P(VDF-TrFE) chain segments between the non-polar helix and polar all-trans phases. The chain segmentation enables structural transformations from the non-polar to the polar phase at modest applied electric fields due to the lowering of the electric enthalpy in the field. The transformations significantly increase the dielectric constant and lead to record electromechanical properties, as recently demonstrated experimentally [1]. We also elucidate the phase transformation energetics and calculate the average induced strain in the segments and the average electroactuation strain. |
Friday, March 10, 2023 1:30PM - 1:42PM |
Z15.00011: Nano-confinement Driven Modulation of Molecular Dipole Orientation and its effect on Ferroelectricity and Work-function in Piezoelectric Polymer Zinnia Mallick The synergistic influence of stress confinement phenomena has recently sparked substantial interest in research on nanoscale piezoelectricity and ferroelectricity in polymers.1,2 Here, we demonstrate how the nanoconfinement driven morphological modification of a model ferroelectric polymer, poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)3.4 into nanoparticles (0D), nanofibers (1D), and thin films (2D) affects molecular dipole orientation on the piezoelectric and ferroelectric capabilities. The molecular dipoles in 1D and 2D nanostructures are perpendicular to the substrate, whereas they are parallel in 0D nanoparticles. This phenomenon significantly controls the nanoscale piezo- and ferro-electric features of the P(VDF-TrFE) in different morphologies. It is noteworthy that the molecule dipole orientation controls the surface functionality and work-function of the nanostructures. Work-functions in 0D and 1D nanostructures range from 5.24 eV and 4.87 eV to 4.72 eV in 2D, respectively. This wide range of work-function tunability was further utilized in effective frictional charge generation owing to the principle of triboelectricity for energy harvesting. This study renders a comprehensive understanding on effect of molecular dipole orientation on the material properties in dimensionally confined nanostructures of P(VDF-TrFE). |
Friday, March 10, 2023 1:42PM - 1:54PM |
Z15.00012: Manipulating interfaces in polymer-nanoparticle composites to affect their energy conversion and storage. Nelson Coates, Andrew Hyslop, Nick Warren, Jennifer Heath, Amelia Schaeffer, Paige Hall, Zion Irving-Singh In solution-processed composite materials such as conducting polymers and nanoparticles, barrier-free thermodynamic phase separation can lead to the formation of interpenetrating continuous networks of components that exhibits a large chemically accessible interfacial area. Although theoretical and experimental results of some conducting polymer-nanoparticle composites have identified the importance of the physicochemical properties of the interface, models of electronic transport in these materials often neglect interfacial effects by using an effective-medium approximation to treat the interpenetrating material as combinations of individual parallel and series phases. Our work has begun to experimentally characterize the interfacial parameters of these composites and identify their impacts on the electrical conductivity and energy dependence of that conductivity beyond the bounds predicted by effective-medium models, with a goal of guiding the design of these materials for thermoelectric energy conversion and capacitive energy storage applications. |
Friday, March 10, 2023 1:54PM - 2:06PM |
Z15.00013: Impact of Lignin Nanofiller on the Water Diffusion and Ionomer Swelling Kinetics of Sulfonated Ionomer Nanocomposites Xueting Wang, Eric M Davis, Mayura Silva, Stephen Creager Creager, Mark Thies, Bronson Lynn Sulfonated poly(ether ether ketone) (SPEEK)-based nanocomposites have emerged as a promising class of proton exchange membranes for vanadium redox flow batteries due to their low cost and comparable proton conductivity to that of the current benchmark material Nafion. For these systems, understanding the interplay between ionomer nanostructure and water/ion transport is critical to the development of more cost-effective, better performing membranes. In this investigation, we investigated the liquid water diffusion and water-induced ionomer swelling kinetics of a series of lignin-SPEEK membranes using in situ time-resolved attenuated total reflectance-Fourier transform infrared (tATR-FTIR) spectroscopy. Specifically, SPEEK nanocomposites containing 5 mass %, 15 mass %, and 25 mass % fractionated lignin, at two lignin MWs (34500 Da and 5470 Da) were fabricated. Further, the two degrees of sulfonation (DS) were applied to investigate how sulfonic acid group density affects the microstructure and properties of the membrane. A three-element viscoelastic relaxation model was applied to capture the water-induced swelling dynamics of the ionomer nanocomposites, while a combined diffusion-relaxation model was used to determine the water diffusion coefficient from the tATR-FTIR water uptake data. The relaxation time constant was seen to decrease markedly after the introduction of lignin and was seen to be proportional to the lignin concentration, indicating a stiffening of the ionomer network. Similarly, the water diffusion coefficient was observed to decrease with the introduction of lignin, though improved water diffusivity was captured at the highest DS, which is consistent with the proton conductivity of these membranes. Results from this study help elucidate the impact of lignin concentration and MW on water diffusion and polymer swelling of SPEEK–lignin ionomer nanocomposites. |
Friday, March 10, 2023 2:06PM - 2:18PM |
Z15.00014: Optimizing Conductivity and Strength of Biodegradable Polymer Graphene Nanoplatelet Nanocomposites via 3D-Printing Yu-Chung Lin Graphene is an incredibly tensile allotrope of carbon with high thermal and electrical conductivity. By blending GNP with biodegradable and non-corrosive polymers, graphene's properties, ductility, and ease of processing can be exploited. An important drawback though is the reduced ductility that occurs when high concentrations of GNP are used. Here we demonstrate how the addition of a second polymer component could be used to engineer blends that achieve the same high thermal and electrical performance, with reduced GNP content. The higher ductility which results also allows this nanocomposite to be extruded into filaments for FDM printing, and if this component is also degradable, the composite is environmentally sustainable and does not introduce toxicity if recycled. For the work presented here, we chose PLA as the second polymer, which is immiscible with iPP and where the interfacial energy with GNP was much higher than that of the particles with iPP. Hence when the two polymers are blended the GNP are expected to aggregate entirely in the iPP phase. This serves to increase the local density of GNP in the iPP phase, achieving percolation at much lower overall concentrations. Based on the results, GNP concentration is directly correlated with increasing electrical and thermal conductivity. At 15% GNP, the maximum electrical conductivity recorded was at the 40/60 iPP/PLA ratio, around 8 S/m at room temperature. At 20% GNP, the maximum conductivity was at the 30/70 iPP/PLA ratio, around 18 S/m. This Study indicates a similarity in the properties of polymer blend to the properties of expensive elements of semiconductors. Optimizing the environmentally beneficial and durable properties of the polymers with electrically and thermally efficient GNPs yields exciting prospects for more sustainable technology and electronic systems. |
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