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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Interphase Engineering Enabled by Using a Separator with Electrochemically Active Carbazole Polymers for Lithium-Ion Batteries

Separators are generally considered inert components in lithium-ion batteries. In the past, some electroactive polymers have been successfully applied in separator modifications for overcharge protection or as acid scavengers. This study highlights the first use of two “electroactive” carbazole polymers (copolymer 9-phenyl-9H-carbazole-phenyl [PCP] and poly(9-vinylcarbazole) [PVC]), which were each applied separately as coatings on the cathode-facing side of commercial Celgard 2325 separators, respectively, to enhance the cycling performance of 0.3Li 2 MnO 3 ·0.7LiMn 0.5 Ni 0.5 O 2 //graphite (LMR-NM//Gr) full cells through interphase engineering. The team observed an irreversible polymer oxidation process of the carbazole-functionalized polymers—occurring only during the first charge—for the modified separator cells, and the results were confirmed by dQ/dV analysis, cyclic voltammetry measurements, and nuclear magnetic resonance characterizations. During this oxidation, carbazole polymers participate in the process of interphase formation, contributing to the improved cycling performance of LMR-NM//Gr batteries. Particularly, oxidation takes place at voltages of ~4.0 and ~3.5 V when PCP and PVC are used as separator coatings, which is highly irreversible. Further postmortem examinations suggest that the improvements using these modified separators arise from the formation of higher-quality and more inorganic SEI, as well as the beneficial CEI enriched in LixPOyFz. These interphases effectively inhibit the crosstalk effect by reducing TM dissolution.

carbazole↗
DOE OSTI2021

Glass-fiber-reinforced polymeric film as an efficient protecting layer for stable Li metal electrodes

With numerous reports on protecting films for stable lithium (Li) metal electrodes, the key attributes for how to construct these efficient layers have rarely been fully investigated. Here, we report a rationally designed hybrid protective layer (HPL) with each component aligning with one key attribute; i.e., cross-linked poly(dimethylsiloxane) (PDMS) enhances flexibility, polyethylene glycol (PEG) provides homogeneous ion-conducting channels, and glass fiber (GF) affords mechanical robustness. A significant improvement of the electrochemical performance of HPL-modified electrodes can be achieved in Li/HPL@Cu half cells, HPL@Li/HPL@Li symmetric cells, and HPL@Li/LiFePO 4 full cells. Even with an industrial standard LiFePO 4 cathode (96.8 wt % active material), the assembled cell still exhibits a capacity retention of 90% after 100 cycles at 1 C. More importantly, the functionality of each component has been studied comprehensively via electrochemical and physical experiments and simulations, which will provide useful guidance on how to construct efficient protective layers for next-generation energy storage devices.

25 ENERGY STORAGE↗
DOE OSTI2025

Truncating 2D Framework Materials Down to a Single Pore: Synthetic Approaches and Opportunities

Here, in this Accounts article, we summarize our recent work on truncating conjugated two-dimensional framework materials down to a single pore, or a single macrocycle. Conjugated 2D architectures have emerged as one of the most synthetically adaptable motifs for coupling semiconductivity and porosity in metal–organic frameworks (MOFs) and covalent organic frameworks (COFs). However, despite their prevalence, 2D architectures have several limitations. In particular, the strong interlayer π–π stacking can limit both processability and the accessibility of internal active sites. We have found that simple macrocycles preserve key aspects of 2D framework structure and function, including porosity and out-of-plane electrical conductivity, while providing improved processability, surface tunability, and mass transport properties. In this article, we first describe our synthetic approach and general design considerations. Specifically, we show how ditopic analogues of the tritopic ligands commonly found in the synthesis of 2D MOFs and COFs can be used to achieve a diverse library of conjugated macrocycles that resemble fragments of semiconducting frameworks in both form and function. The length of the peripheral side chains, the size of the aromatic core, and the solubility of intermediates are all key variables in favoring selective macrocycle formation over undesired linear polymers and oligomers. Next, we highlight the unique advantages that macrocycles provide, including improved processability, atomically precise surface tunability, and greater active site accessibility. In particular, the identity of the peripheral side chains dramatically impacts both solubility and colloidal stability as well as crystal size and morphology. We further show how the solution processability and nanoscale dimensions of macrocycles can simplify electronic device fabrication and improve electrochemical performance. Finally, we end with a forward-looking discussion on how macrocycles offer a unique bridge between conjugated molecules and extended frameworks, enabling new application areas and fundamental science.

charge transport↗
DOE OSTI2023

Relative-Humidity Dependence of Electrochemically Active Surface Area in Porous Carbon Catalyst Layers

Polymer-electrolyte fuel cells (PEFCs) utilize porous catalyst layers (CLs) formed of carbon supports on which Pt particles are deposited and ionomer films are distributed. Carbon supports themselves have varying degrees of porosity, where high-surface-area carbon (HSC) supports possess nanometer-sized interior pores that are suitable for Pt nanoparticle deposition but prevent deleterious ionomer penetration. However, this requires protons to transport through water pathways inside the pores. To understand the generation of such pathways, we examine the various mechanisms of water uptake by PEFC CLs, and the subsequent impact of water uptake on Pt utilization through developing a multiphysics model of the water wetting phenomena as a function of relative humidity. The model details water uptake via ionomer absorption, capillary condensation in the hydrophilic pores, and surface adsorption using molecular potential that account for various water and surface dipole interactions. The results quantify how mesoporous carbons with highly hydrophilic pores increase Pt utilization through the development of wetted layers, which at the same time enable optimized gas-transport pathways. It also demonstrates the impact of pore-size distribution (PSD) and physical and chemical parameters on the water uptake phenomena, allowing for future CL particle and structure optimization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Synthesis of hyperbranched polymer films via electrodeposition and oxygen-tolerant surface-initiated photoinduced polymerization

Hypothesis Hyperbranched polymers, not only possess higher functionality, but are also easier to prepare compared to dendrimers and dendric polymers. Combining electrodeposition and surface-initiated photoinduced electron transfer-reversible addition-fragmentation chain transfer (SI-PET-RAFT) polymerization is hypothesized to be a novel strategy for preparing hyperbranched polymer films on conductive surfaces without degassing. Experiments In this study, polymer brush grafted films with four different architectures (i.e. linear, branched, linear- block -branched, and branched- block -linear) were prepared on gold-coated glass substrates using electrodeposition, followed by SI-PET-RAFT polymerization. The resulting film structure and thickness, surface topology, absorption property, and electrochemical behavior were confirmed by spectroscopy, microscopy, microbalance technique, and impedance measurement. Findings These hyperbranched polymer brushes were capable of forming a thicker but more uniformly covered films compared to linear polymer brush films, demonstrating that hyperbranched polymer films can be potentially useful for fabricating protective polymer coatings on various conductive surfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Rigid-Rod Sulfonated Polyamide as an Aqueous-Processable Binder for Li-Ion Battery Electrodes

Polymer binders are important components of most battery electrodes, ensuring high performance and long-term durability. Increasing demand for lithium-ion batteries in the automotive, stationary power, and portable electronics industries calls for a greener binder to replace poly(vinylidene difluoride) (PVDF). We evaluate the performance of aqueous solution-processed electrodes prepared with a rigid-rod polymer binder, poly(2,2'-disulfonyl-4,4'-benzidine terephthalamide) (PBDT). The polyamide backbone and double-helical configuration of PBDT give rise to its mechanical strength and rigidity, and its functional nature (H-bonding amides and sulfonates) can provide specific binding with electrode particles. LiFePO 4 electrodes prepared with 3 wt% PBDT show mechanical integrity and cycling stability, achieving over 1000 cycles at 4C rate with negligible capacity decay. These electrodes demonstrate comparable rate performance with their PVDF counterparts while eliminating fluorine from the electrode as well as the organic solvents needed for processing. Furthermore, this study reveals that PBDT holds great potential as a binder for advanced sustainable batteries.

25 ENERGY STORAGE↗
DOE OSTI2022

Proton Tunable Analog Transistor for Low Power Computing

This project was broadly motivated by the need for new hardware that can process information such as images and sounds right at the point of where the information is sensed (e.g. edge computing). The project was further motivated by recent discoveries by group demonstrating that while certain organic polymer blends can be used to fabricate elements of such hardware, the need to mix ionic and electronic conducting phases imposed limits on performance, dimensional scalability and the degree of fundamental understanding of how such devices operated. As an alternative to blended polymers containing distinct ionic and electronic conducting phases, in this LDRD project we have discovered that a family of mixed valence coordination compounds called Prussian blue analogue (PBAs), with an open framework structure and ability to conduct both ionic and electronic charge, can be used for inkjet-printed flexible artificial synapses that reversibly switch conductance by more than four orders of magnitude based on electrochemically tunable oxidation state. Retention of programmed states is improved by nearly two orders of magnitude compared to the extensively studied organic polymers, thus enabling in-memory compute and avoiding energy costly off-chip access during training. We demonstrate dopamine detection using PBA synapses and biocompatibility with living neurons, evoking prospective application for brain - computer interfacing. By application of electron transfer theory to in-situ spectroscopic probing of intervalence charge transfer, we elucidate a switching mechanism whereby the degree of mixed valency between N-coordinated Ru sites controls the carrier concentration and mobility, as supported by density functional theory (DFT) .

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2020

Durability evaluation of a Fe–N–C catalyst in polymer electrolyte fuel cell environment via accelerated stress tests

In this work, an “atomically-dispersed” iron-nitrogen-carbon (Fe–N–C) catalyst was used to provide a systematic comparison of platinum group metal (PGM)-free electrocatalyst degradation as a function of accelerated stress tests (ASTs) in an acidic polymer electrolyte fuel cell (PEFC). It was determined that the majority of catalyst degradation was caused by cell operation in presence of O 2 . In contrast, potential cycling of the Fe–N–C-containing cathode under inert atmosphere over typical PEFC cathode operation from 0.95 to 0.6 V had little to no effect. The increase in kinetic overpotential is shown to be the major source of the PEFC performance decrease during the ASTs. These results continue to showcase the need for development of robust PGM-free electrocatalysts in concert with improved electrochemical performance.

25 ENERGY STORAGE↗
DOE OSTI2024

Side chain engineering in indacenodithiophene- co -benzothiadiazole and its impact on mixed ionic–electronic transport properties

Organic semiconductors are increasingly being decorated with hydrophilic solubilising chains to create materials that can function as mixed ionic–electronic conductors, which are promising candidates for interfacing biological systems with organic electronics. While numerous organic semiconductors, including p- and n-type materials, small molecules and polymers, have been successfully tailored to encompass mixed conduction properties, common to all these systems is that they have been semicrystalline materials. Here, we explore how side chain engineering in the nano-crystalline indacenodithiophene-co-benzothiadiazole (IDTBT) polymer can be used to instil ionic transport properties and how this in turn influences the electronic transport properties. This allows us to ultimately assess the mixed ionic–electronic transport properties of these new IDTBT polymers using the organic electrochemical transistor as the testing platform. Using a complementary experimental and computational approach, we find that polar IDTBT derivatives can be infiltrated by water and solvated ions, they can be electrochemically doped efficiently in aqueous electrolyte with fast doping kinetics, and upon aqueous swelling there is no deterioration of the close interchain contacts that are vital for efficient charge transport in the IDTBT system. Despite these promising attributes, mixed ionic–electronic charge transport properties are surprisingly poor in all the polar IDTBT derivatives. Albeit a “negative” result, this finding clearly contradicts established side chain engineering rules for mixed ionic–electronic conductors, which motivated our continued investigation of this system. We eventually find this anomalous behaviour to be caused by increasing energetic disorder in the polymers with increasing polar side chain content. We have investigated computationally how the polar side chain motifs contribute to this detrimental energetic inhomogeneity and ultimately use the learnings to propose new molecular design criteria for side chains that can facilitate ion transport without impeding electronic transport.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Practical Considerations for Testing Polymer Electrolytes for High-Energy Solid-State Batteries

Polymer electrolytes are an important class of materials in enabling solid-state batteries, which have the potential to exceed 400 Wh/kg energy density. Despite significant advancements in their lithium-ion transport and mechanical properties over the last two decades, the integration and testing of these novel electrolyte materials into functioning cells with the electrode loadings and dimensions required to meet the cell-level energy density goals have been limited. Here, through multiple representative examples, we demonstrate the need of testing in close to practical cell conditions for a faster and more reliable evaluation of polymeric electrolytes. In particular, the need for testing with thin lithium anodes and practical cycling capacities is demonstrated for evaluation of their lithium-metal interfacial stability and dendritic resistance, respectively, and a testing protocol is suggested. The guidelines presented here will also apply to testing of other solid electrolytes for solid-state batteries.

25 ENERGY STORAGE↗
DOE OSTI2024

Triggering C-N Coupling on Metal Oxide Nanocomposite for the Electrochemical Reduction of CO 2 and NO x ⁻ to Formamide

The co-electroreduction of CO 2 and NO x ⁻ (NO 3 ⁻ /NO 2 ⁻ ) to generate formamide (HCONH 2 ) offers an opportunity for downstream chemical and polymer manufacturing decarbonization; however, significant challenges lie in the C-N coupling and the associated low product selectivity. Herein, p-block metal oxides are incorporated in copper oxides to provide more accessible active sites for reactant adsorption and activation, tuning the reaction selectivity toward the formamide production. Through in situ Raman and synchrotron-based infrared spectroscopy measurements, C-N bond formation is demonstrated in real-time with the CuO x /BiO x catalyst, where the C-N bond is detected via a *CHO and *NH 2 intermediates formation, in agreement with the density functional theory calculations. When tested in a flow electrolyzer, a formamide yield rate of 134 ± 11 mmol h -1 g cat -1 is reported, the first report of co-electroreduction of CO 2 and NO x ⁻ to formamide beyond conventional H-cell measurements. These new insights on the C-N coupling mechanisms and scale-up capability provide directions for further development of electrocatalysts for the formamide production.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Design of robust and versatile hydrocarbon-based single-ion-conducting polymer electrolytes

Hydrocarbon-based polymers offer several advantages, including lower environmental impacts, cost effectiveness, and the ability to finely tune properties. Here, we have developed trifluoromethanesulfonimide (TFSI)-functionalized poly(norbornene) (PNB) polymers utilizing a specifically designed oxa-Michael addition of a vinyl TFSI anion to an alcohol. Our results reveal that PNB-TFSI derivatives exhibit superior thermal stability and mechanical robustness compared with Nafion. The optimized PNB-TFSI-H-48 polymer (IEC 1.86 mmol/g) exhibits equivalent performance to Nafion as an anode ionomer in a proton exchange membrane fuel cell. Exchanging the counter ion to Li + enables PNB-TFSI to be used for Li-ion battery applications. Propylene carbonate plasticized PNB-TFSI derivatives achieve an Li-ion conductivity of over 10 −5 S/cm at 30°C. This Li polymer electrolyte exhibits excellent electrochemical stability (5 V vs. Li + /Li) and good cycling in a Li symmetric cell. These results highlight the potential and rational design of PNB-TFSI polymers for next-generation energy storage and conversion technologies.

08 HYDROGEN↗
DOE OSTI2021

Chemical Modifications of Ag Catalyst Surfaces with Imidazolium Ionomers Modulate H 2 Evolution Rates during Electrochemical CO 2 Reduction

Bridging polymer design with catalyst surface science is a promising direction for tuning and optimizing electrochemical reactors that could impact long-term goals in energy and sustainability. Particularly, the interaction between inorganic catalyst surfaces and organic-based ionomers provides an avenue to both steer reaction selectivity and promote activity. In this work, we studied the role of imidazolium-based ionomers for electrocatalytic CO 2 reduction to CO (CO 2 R) on Ag surfaces and found that they produce no effect on CO 2 R activity yet strongly promote the competing hydrogen evolution reaction (HER). By examining the dependence of HER and CO 2 R rates on concentrations of CO 2 and HCO 3 –, we developed a kinetic model that attributes HER promotion to intrinsic promotion of HCO 3 – reduction by imidazolium ionomers. We also show that varying the ionomer structure by changing substituents on the imidazolium ring modulates the HER promotion. This ionomer-structure dependence was analyzed via Taft steric parameters and density functional theory calculations, which suggest that steric bulk from functionalities on the imidazolium ring reduces access of the ionomer to both HCO 3 – and the Ag surface, thus limiting the promotional effect. Our results help develop design rules for ionomer–catalyst interactions in CO 2 R and motivate further work into precisely uncovering the interplay between primary and secondary coordination in determining electrocatalytic behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Electrochemical Capacitance Traces with Interlayer Spacing in Two‐dimensional Conductive Metal–Organic Frameworks

Abstract Electrically conductive metal–organic frameworks (MOFs) are promising candidates for electrochemical capacitors (EC) for fast energy storage due to their high specific surface areas and potential for redox activity. To maximize energy density, traditional inorganic pseudocapacitors have utilized faradaic processes in addition to double‐layer capacitance. Although conductive MOFs are usually comprised of redox active ligands which allow faradaic reactions upon electrochemical polarization, systematic studies providing deeper understanding of the charge storage processes and structure‐function relationships have been scarce. Here, we investigate the charge storage mechanisms of a series of triazatruxene‐based 2D layered conductive MOFs with variable alkyl functional groups, Ni 3 (HIR 3 ‐TAT) 2 (TAT=triazatruxene; R=H, Et, n ‐Bu, n ‐Pent). Functionalization of the triazatruxene core allows for systematic variation of structural parameters while maintaining in‐plane conjugation between ligands and metals. Specifically, R groups modulate interlayer spacing, which in turn shifts the charge storage mechanism from double‐layer capacitance towards pseudocapacitance, leading to an increase in molar specific capacitance from Ni 3 (HIH 3 ‐TAT) 2 to Ni 3 (HIBu 3 ‐TAT) 2 . Partial exfoliation of Ni 3 (HIBu 3 ‐TAT) 2 renders redox active ligand moieties more accessible, and thus increases the dominance of faradaic processes. Our strategy of controlling charge storage mechanism through tuning the accessibility of redox‐active sites may motivate further design and engineering of electrode materials for EC.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Selective and Chemical-Free Removal of Toxic Heavy Metal Cations from Water Using Shock Ion Extraction

Electrochemical methods are known to have attractive features and capabilities when used for ion separations and water purification. In this study, we developed a new process called shock ion extraction (shock IX) for selective and chemical-free removal of toxic heavy metals from water. Shock IX is a hybrid process that combines shock electrodialysis (shock ED) and ion exchange using an ion exchange resin wafer (IERW), and this method can be thought of functionally as an electrochemically assisted variation of traditional ion exchange. In particular, shock IX exhibits greater ion removal and selectivity for longer periods of time, compared to the use of ion exchange alone. Here, the use of an IERW in shock ED also increases multivalent ion selectivity, reduces energy consumption, and improves the hydrodynamics and scalability of the system.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

Damage-free X-ray spectroscopy characterization of oxide thin films

Thin polymer or oxide films are ubiquitous components in many devices, including membranes for filtration or electrodes in electrochemical energy storage. High energy electron or x-ray probes for microscopy and spectroscopy are useful to characterize and understand these materials. However, irreversible damage by the probe radiation remains a challenge. Here, we show that graphene serves as an x-ray and electron transparent substrate that substantially reduces radiation damage of an oxide thin film. We demonstrate this using highly focused x-ray beams, which show that compared to oxide thin films supported on a substrate, graphene-supported regions show minimal changes in the x-ray spectra as a function of x-ray dose. Further, these results pave the way for the development of experimental setups that allow for long exposure time measurements with limited sample damage and substrate-directed radiation patterning.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Design of a multi-functional gel polymer electrolyte with a 3D compact stacked polymer micro-sphere matrix for high-performance lithium metal batteries

We report lithium metal batteries (LMBs) are considered as promising high energy density batteries. However, they still suffer from poor cyclability due to the instability of solid electrolyte interphases (SEIs) and Li dendrite issues. Herein, a novel 3D densely packed multifunctional crosslinked gel polymer electrolyte (PHGPE) has been synthesized by in situ copolymerization of pentaerythritol tetraacrylate and 2-hydroxyethyl acrylate in a liquid electrolyte via a thermal initiation method. Due to intermolecular hydrogen bonding in the frameworks, the PHGPE exhibits a 3D compact-stacked and crosslinked micro-sphere structure, which benefits the construction of homogeneous Li + flux, enabling uniform Li plating/stripping and formation of robust SEIs onto the lithium electrode. Benefiting from the above advantages, symmetric Li cells in the PHGPE deliver excellent cyclabilities of 6000 h at a current density of 1 mA cm -2 (1 mA h cm -2 ) and 7700 h at 0.5 mA cm -2 (2 mA h cm -2 ). Moreover, the PHGPE has such a wide electrochemical window that it is compatible with both high-voltage LiNi 0.8 Co 0.1 Mn 0.1 O 2 and sulfur cathodes to realize long cycle life. Additionally, a LiFePO 4 based pouch size LMB also presents promising performance. Therefore, this study of the PHGPE has opened a new avenue for high-performance LMBs with excellent versatility and practicality.

25 ENERGY STORAGE↗
DOE OSTI2021

Electrospun Composite Proton-Exchange and Anion-Exchange Membranes for Fuel Cells

A fuel cell is an electrochemical device that converts the chemical energy of a fuel and oxidant into electricity. Cation-exchange and anion-exchange membranes play an important role in hydrogen fed proton-exchange membrane (PEM) and anion-exchange membrane (AEM) fuel cells, respectively. Over the past 10 years, there has been growing interest in using nanofiber electrospinning to fabricate fuel cell PEMs and AEMs with improved properties, e.g., a high ion conductivity with low in-plane water swelling and good mechanical strength under wet and dry conditions. Electrospinning is used to create either reinforcing scaffolds that can be pore-filled with an ionomer or precursor mats of interwoven ionomer and reinforcing polymers, which after suitable processing (densification) form a functional membrane. In this review paper, methods of nanofiber composite PEMs and AEMs fabrication are reviewed and the properties of these membranes are discussed and contrasted with the properties of fuel cell membranes prepared using conventional methods. The information and discussions contained herein are intended to provide inspiration for the design of high-performance next-generation fuel cell ion-exchange membranes.

25 ENERGY STORAGE↗