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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

An Efficient Bifunctional Air Electrode for Reversible Protonic Ceramic Electrochemical Cells

One of the main bottlenecks that limits the performance of reversible protonic ceramic electrochemical cells (R-PCECs) is the sluggish kinetics of the oxygen reduction and evolution reactions (ORR and OER). Here, the significantly enhanced ORR and OER kinetics and stability of a conventional La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF) air electrode by an efficient catalyst coating of barium cobaltite (BCO) is reported. The polarization resistance of a BCO-coated LSCF air electrode at 600 oC is 0.16 Ω cm 2 , about 30% of that of the bare LSCF air electrode under the same conditions. Further, a R-PCEC with the BCO-coated LSCF air electrode shows exceptional performance in both fuel cell (maximum power density of 1.16 W cm -2 at 600 ºC) and electrolysis (current density of 1.80 A cm -2 at 600 ºC at 1.3 V) modes. Finally, the performance enhancement is attributed mainly to the facilitated rate of oxygen surface exchange.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2017

Engineering Ultrathin Polyaniline in Micro/Mesoporous Carbon Supercapacitor Electrodes Using Oxidative Chemical Vapor Deposition

In this work, oxidative chemical vapor deposition (oCVD) is demonstrated to enable the integration of nanometer-thin polyaniline (PANI) that significantly improves charge storage capacity of supercapacitors utilizing carbide-derived carbon (CDC) with a bimodal (micro/mesoporous) pore size distribution. To our knowledge, this work is the first reported synthesis of PANI via oCVD. The oCVD process allows for the integration of PANI into pores as small as 1.7 nm, and resulting CDC/PANI electrodes have a gravimetric capacitance more than twice that of bare CDC (136 F g -1 for 11 wt% of PANI in the CDC electrode versus 60 F g -1 for bare Mo 2 C-CDC at 10 mV s -1 ). This yields a PANI-only gravimetric capacitance of ≈690 F g -1 , which is close to the theoretical value of 750 F g -1 . The coating preserves the native electrode surface area and pore size distribution, while improving capacitance due to the faradaic redox reactions of PANI. Even at high scan rates of over 100 mV s -1 , the added pseudocapacitance from PANI remains evident. Finally, the composite electrode exhibits good cyclability, decreasing to 90% of the initial value (≈100 F g -1 ) after 10 000 cycles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

3D Self-Architectured Steam Electrode Enabled Efficient and Durable Hydrogen Production in a Proton-Conducting Solid Oxide Electrolysis Cell at Temperatures Lower Than 600 °C

Hydrogen production via water electrolysis using solid oxide electrolysis cells (SOECs) has attracted considerable attention because of its favorable thermodynamics and kinetics. It is considered as the most efficient and low-cost option for hydrogen production from renewable energies. By using proton-conducting electrolyte (H-SOECs), the operating temperature can be reduced from beyond 800 to 600 °C or even lower due to its higher conductivity and lower activation energy. Technical barriers associated with the conventional oxygen-ion conducting SOECs (O-SOECs), that is, hydrogen separation and electrode instability that is primarily due to the Ni oxidation at high steam concentration and delamination associated with oxygen evolution, can be remarkably mitigated. Here, a self-architectured ultraporous (SAUP) 3D steam electrode is developed for efficient H-SOECs below 600 °C. At 600 °C, the electrolysis current density reaches 2.02 A cm –2 at 1.6 V. Instead of fast degradation in most O-SOECs, performance enhancement is observed during electrolysis at an applied voltage of 1.6 V at 500 °C for over 75 h, attributed to the “bridging” effect originating from reorganization of the steam electrode. The H-SOEC with SAUP steam electrode demonstrates excellent performance, promising a new prospective for next-generation steam electrolysis at reduced temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Self‐Standing Carbon Nanofibers@Carbon Felt Electrodes to Boost Electrolyzer Productivity: Application to the Electro‐Manufacturing of trans ‐3‐Hexenedioic Acid and Adipic Acid

The industrial implementation of electrosynthesis for chemical manufacturing remains constrained by the limited surface area of conventional electrodes. Herein, this challenge is addressed by designing a carbon nanofiber@carbon felt (CNF@CF) electrode platform that combines the high conductivity, flexibility, and ease of handling of commercial carbon felts (CF) with the large surface area and tunable surface chemistry of carbon nanofibers (CNFs). CNFs are deliberately grown onto the CF scaffold to form a sword-in-sheath structure, where entangled nanofibers wrap the felt macrofibers to provide excellent mechanical stability and electrical conductivity without binders. CNF@CF is evaluated both as an electrode and as a catalyst support for the electrochemical hydrogenation of cis,cis-muconic acid (ccMA), a biobased platform molecule key to the production of performance polyamides and renewable Nylon 6,6. As a noncatalytic electrode for the partial hydrogenation to trans-3-hexenedioic acid, CNF@CF achieves a threefold increase in both cumulative productivity and Faradaic efficiency (FE) compared to bare CF. A similar boost in catalytic activity and energy efficiency is observed using Pd/CNF@CF for the hydrogenation of ccMA to adipic acid. These results highlight the opportunities of the CNF@CF platform for electro-organic synthesis and sustainable chemical manufacturing.

electrochemical hydrogenation↗
DOE OSTI2022

A Comparative Study of Compressive Effects on the Morphology and Performance of Carbon Paper and Cloth Electrodes in Redox Flow Batteries

Compressing porous carbon electrodes is a common approach to improve flow battery performance, but the resulting impact on electrode structure, fluid dynamics, and cell performance is not well understood. Herein, microtomographic imaging, load cell testing, and flow cell diagnostics are employed to characterize how compression‐induced changes impact pressure drop, polarization, and mass‐transfer scaling. Five different compressions are tested, spanning ranges typically used in literature, for AvCarb 1071 cloth (0%, 9%, 20%, 25%, 32%) and Freudenberg H23 paper (0%, 8%, 12%, 17%, 22%). It is found that the two electrode structures have distinct responses to compression, resulting in differing optimal conditions identified for each material; specifically, the Freudenberg H23 exhibits lower combined ohmic, charge‐transfer, and mass‐transport values at 8% compression, resulting in improved electrochemical performance across all compressive values, as compared to the optimal AvCarb 1071 compression (20%). Overall, Freudenberg H23 exhibits a greater sensitivity to compression with peak electrochemical activity correlating with increased permeability, whereas AvCarb 1071 is insensitive to compressive loads but produces lower electrochemical performance. Herein, the trade‐offs of mechanical robustness on fluid‐dynamic and electrochemical performance between the two electrodes are demonstrated by the aforementioned findings, suggesting each could be used for specific operating environments.

25 ENERGY STORAGE↗
DOE OSTI2021

A Comparison of Solid Electrolyte Interphase Formation and Evolution on Highly Oriented Pyrolytic and Disordered Graphite Negative Electrodes in Lithium–Ion Batteries

The presence and stability of solid electrolyte interphase (SEI) on graphitic electrodes is vital to the performance of lithium-ion batteries (LIBs). However, the formation and evolution of SEI remain the least understood area in LIBs due to its dynamic nature, complexity in chemical composition, heterogeneity in morphology, as well as lack of reliable in situ/operando techniques for accurate characterization. In addition, chemical composition and morphology of SEI are not only affected by the choice of electrolyte, but also by the nature of the electrode surface. While introduction of defects into graphitic electrodes has promoted their electrochemical properties, how such structural defects influence SEI formation and evolution remains an open question. In this work, utilizing nondestructive operando electrochemical atomic force microscopy (EChem-AFM) the dynamic SEI formation and evolution on a pair of representative graphitic materials with and without defects, namely, highly oriented pyrolytic and disordered graphite electrodes, are systematically monitored and compared. Complementary to the characterization of SEI topographical and mechanical changes during electrochemical cycling by EChem-AFM, chemical analysis and theoretical calculations are conducted to provide mechanistic insights underlying SEI formation and evolution. The results provide guidance to engineer functional SEIs through design of carbon materials with defects for LIBs and beyond.

25 ENERGY STORAGE↗
DOE OSTI2017

Understanding limiting factors in thick electrode performance as applied to high energy density Li-ion batteries

We present that increasing electrode thickness, thus increasing the volume ratio of active materials, is one effective method to enable the development of high energy density Li-ion batteries. In this study, an energy density versus power density optimization of LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA)/graphite cell stack was conducted via mathematical modeling. The energy density was found to have a maximum point versus electrode thickness (critical thickness) at given discharging C rates. The physics-based factors that limit the energy/power density of thick electrodes were found to be increased cell polarization and underutilization of active materials. The latter is affected by Li-ion diffusion in active materials and Li-ion depletion in the electrolyte phase. Based on those findings, possible approaches were derived to surmount the limiting factors. Finally, the improvement of the energy–power relationship in an 18,650 cell was used to demonstrate how to optimize the thick electrode parameters in cell engineering.

25 ENERGY STORAGE↗
DOE OSTI2024

Amorphous Iridium Oxide-Integrated Anode Electrodes with Ultrahigh Material Utilization for Hydrogen Production at Industrial Current Densities

Herein, ionomer-free amorphous iridium oxide (IrO x ) thin electrodes are first developed as highly active anodes for proton exchange membrane electrolyzer cells (PEMECs) via low-cost, environmentally friendly, and easily scalable electrodeposition at room temperature. Combined with a Nafion 117 membrane, the IrO x -integrated electrode with an ultralow loading of 0.075 mg cm –2 delivers a high cell efficiency of about 90%, achieving more than 96% catalyst savings and 42-fold higher catalyst utilization compared to commercial catalyst-coated membrane (2 mg cm –2 ). Additionally, the IrO x electrode demonstrates superior performance, higher catalyst utilization and significantly simplified fabrication with easy scalability compared with the most previously reported anodes. Notably, the remarkable performance could be mainly due to the amorphous phase property, sufficient Ir 3+ content, and rich surface hydroxide groups in catalysts. Overall, due to the high activity, high cell efficiency, an economical, greatly simplified and easily scalable fabrication process, and ultrahigh material utilization, the IrO x electrode shows great potential to be applied in industry and accelerates the commercialization of PEMECs and renewable energy evolution.

08 HYDROGEN↗
DOE OSTI2020

The polymeric conformational effect on capacitive deionization performance of graphene oxide/polypyrrole composite electrode

Exploitation of novel faradic materials is an alternative implementation for solving the problem of poor specific electrosorption capacity that conventional carbon materials are encountered in capacitive deionization. Particularly, composite electrode is just a suitable choice because of its potentially high ion-storage ability. Herein, a cyclic voltammetric treatment method with different low limit of potential window was used to manipulate the polymeric conformation and doping level of graphene oxide/polypyrrole (GO/PPy) composite electrode. Based on it, the effect of polymeric structure on the electrosorption performance was systematically studied. When the low limit of potential window is shifted negatively enough, the irreversible polymeric conformational shrinks of GO/PPy are promoted, which not only hinders the insertion process of ions, but also decreases the doping level of polymer due to the intensive interchain-action produced by more entangled polymeric chain. Thus, the number of intercalated ions should decrease, which is expressed by electrochemical impedance spectroscopy (EIS) results and is proportional to the electrosorption capacity of GO/PPy composite electrode in membrane capacitive deionization (MCDI) process. Finally, our work suggests that the less packing density, higher doping level and more charge delocalization on PPy backbone in electrode are beneficial to enhance its capacitive deionization performance.

42 ENGINEERING↗
DOE OSTI2018

Calendar-life versus cycle-life aging of lithium-ion cells with silicon-graphite composite electrodes

The use of blended silicon-graphite (Si-Gr) negative electrodes increases the energy density of lithium-ion cells over those containing only graphite (Gr) electrodes. However, volume changes in the Si particles that occur during cycling causes deterioration of the solid-electrolyte interphase (SEI) layer on the particles resulting in further electrolyte reduction that immobilizes Li+ ions and, therefore, capacity fade. Because the volume changes are not expected to occur during a potentiostatic hold (referred to as calendar-life aging), by comparison of cycle-life and calendar-life aged cells one can expect to assess the role of volume changes in the deterioration of cell performance. To this end, cells with Si-Gr and Gr negative electrodes (and Li 1.03 (Ni 0.5 Co 0.2 Mn 0.3 ) 0.97 O 2 containing positive electrodes) were assembled, tested, and compared using cycle-life and calendar-life aging protocols. As expected, the capacity loss of the cycle-life aged cells was higher than that of the calendar-life aged cells. However, the measurable capacity loss for the calendar-life aged cells indicated continued immobilization of Li + ions. Furthermore, electrolytes extracted from the calendar-life aged cells showed more LiPF 6 hydrolysis products than those extracted from the cycle-life aged cells. In conclusion, we discuss possible mechanistic causes for the observed aging behaviors in this article.

25 ENERGY STORAGE↗
DOE OSTI2024

Impact of reactor architecture and design parameters on the performance of microbial electrolysis cells revealed by the electrode potential slope analysis

Microbial electrolysis cells (MECs) are appealing for recovering the chemical energy contained in domestic and industrial liquid wastes as hydrogen gas. Despite several years of research in the field, there is still a lack of critical analysis of how the reactor architecture dictates the electrochemical performance of the cell. In this study, internal resistance and onset voltage from the electrode potential slope analysis (EPS) were used in combination with current density, hydrogen production rate, reactor packing density, electrode spacing, membrane type and composition from 23 different studies to identify the reactor design parameters that primarily govern electrochemical performance of MECs. Using anion exchange membranes resulted in smaller internal resistances (AEM R int = 41± 40 mΩ m 2 ) and larger current density (18 ± 14 A m −2 ) compared to single chamber reactors (SC R int = 68 ± 58 mΩ m 2 ; 22 ± 16 A m −2 ) or MECs with cation exchange membranes (CEM R int = 376 ± 280 mΩ m 2 ; 3.0 ± 2.1 A m −2 ). Higher electrochemical performance for AEM- and SC-MECs translated in larger hydrogen gas production rates (0.122 mL H 2 C −1 for AEM vs 0.117 mL H 2 C −1 for SC), but only when inhibitors against hydrogen scavengers were added in single chamber systems (0.080 mL H 2 C −1 for SC without inhibitors). Following membrane type and composition, maintaining a small electrode spacing was the most critical parameter to improve MEC performance, indicating that the low conductivity of the media primarily limit performance by increasing ohmic resistance. Here, reactor volume and electrode surface area negatively correlated with internal resistance and current density, indicating that better performance of scaled-up reactors can likely be obtained by stacking multiple smaller units rather than just increasing reactor size. Although challenges remain in the implementation of MECs for hydrogen production from liquid wastes, advances in electrochemical engineering of the reactors can facilitate scale up and performance prediction at scale.

Electrochemistry↗
DOE OSTI2025

Enhancing water and oxygen transport through electrode engineering for AEM water electrolyzers

Anion-exchange membrane water electrolyzers (AEMWEs) can accelerate the deployment of more efficient and affordable hydrogen production solutions. Here, electrode structure is shown to affect water back-diffusion and oxygen transport, which, in return, governs overpotential behaviors in AEMWEs. Measurements indicate that electrode with copious catalytic sites produces water close to the AEM, creating a higher water gradient and driving water back-diffusion, which improves membrane hydration and mass transport. In situ measurement reveals a high pH gradient near the anode surface, which affects anode kinetics. Operando measurement shows reduced oxygen accumulation when decoupling oxygen production and transport on anode. Catalyst ink rheology and stability are tuned with additives to realize scalable fabrication of electrodes with enhanced transport features, allowing AEMWE to operate at 2 A cm−2 for over 1,000+ h at a 2.3 μV h−1 degradation rate. Analysis during and post-durability provides insights into degradation mechanisms. This work demonstrates an electrode design strategy for efficient and durable AEMWEs.

AEM↗
DOE OSTI2017

High performance binder-free SiO x /C composite LIB electrode made of SiO x and lignin

A high performance binder-free SiO x /C composite electrode was synthesized by mixing SiO x particles and Kraft lignin in a cryo-mill followed by heat treatment at 600 °C. After the heat treatment, lignin formed a conductive matrix hosting SiO x particles, ensuring electronic conductivity, connectivity, and accommodation of volume changes during lithiation/delithiation. As the result, no conventional binder or conductive agent was necessary. When electrochemically cycled, the composite electrode delivered excellent performance, maintaining ~900 mAh g -1 after 250 cycles at a rate of 200 mA g -1 , and good rate capability. The robustness of the electrode was also examined by post-cycling SEM images, where few cracks were observed. The excellent electrochemical performance can be attributed to the comparatively small volume change of SiO x -based electrodes (160%) and the flexibility of the lignin derived carbon matrix to accommodate the volume change. In conclusion, this work should stimulate further interests in using bio-renewable resources in making advanced electrochemical energy storage systems.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Probing lithiation and delithiation of thick sintered lithium-ion battery electrodes with neutron imaging

As lithium-on (Li-ion) batteries increase in their prevalence and the range of applications expands, there is a need to understand and exploit the limits of electrochemical performance. Probing the internal processes in Li-ion batteries provides insights into the electrochemical characteristics of the cells as well as information necessary for rational cell design. In this manuscript an in situ method, neutron imaging, is applied to Li-ion full cells to track the lithiation/delithiation processes in the electrodes during discharge. The electrodes comprise thick sintered films of only active material, which improves the number of discrete points that are mapped for net changes in neutron intensity through the electrode. The lithiation/delithiation processes are qualitatively consistent with calculations of the Li + concentration and discharge profiles of the cells. These results illustrate that neutron imaging can experimentally probe and confirm limitations in the electrochemical performance of Li-ion full cells, particularly those with thick electrodes.

25 ENERGY STORAGE↗
DOE OSTI2020

Optimization of Graphite–SiO blend electrodes for lithium-ion batteries: Stable cycling enabled by single-walled carbon nanotube conductive additive

Lithium-alloying materials are of great interest to improve the gravimetric and volumetric energy density of lithium-ion batteries, though their associated volume fluctuation with cycling often leads to poor cycling performance. Active-inactive alloys and blending alloys with carbon materials are common strategies to accommodate volume fluctuation. Herein we set out to optimize graphite-SiO blend electrode formulations to eliminate rapid capacity fade. Electrodes with highly stable cycling were prepared by simple planetary mixing procedures, enabled by the use of just a fraction of a weight percent of commercial SWCNTs as the only conductive additive, and by the appropriate choice of binder/stabilizing agent. In fact, the use of SWCNTs allowed for graphite-free SiO electrodes with approximately 74% higher volumetric energy density relative to traditional graphite electrodes, and superior capacity retention in coin-type full-cell testing versus NMC532 cathodes.

25 ENERGY STORAGE↗
DOE OSTI2020

Impact of electrode thick spot irregularities on polymer electrolyte membrane fuel cell initial performance

Polymer electrolyte membrane fuel cells have great potential for power generation in many applications, but to implement them on a larger scale, understanding of quality requirements, tolerances, and controls during manufacturing must improve. As part of this broad challenge, irregularities resulting from the membrane electrode assembly production process must be studied to determine if they impact the performance of the cell. One potential irregularity is a locally increased thickness of the coated or deposited electrode. In order to understand and provide insight into the impact of such irregularities, we intentionally created thick spots in the center of cathode electrodes. The thick spots fabricated by two different approaches were carefully characterized by optical microscopy, X-ray fluorescence spectroscopy and scanning electron microscopy (SEM). We found that the impact of the thick spots on the electrochemically active catalyst area and mass activity was minimal. However, specific electrode thick spot irregularities significantly impacted the mass transport properties of the cells. Based on SEM analysis, the likely cause of the performance drop is morphological changes associated with the creation of the thick spot irregularity. Spatial performance results obtained with a segmented cell system further indicated that the area of the performance impact exceeded that of the intentionally created thick spot.

25 ENERGY STORAGE↗
DOE OSTI2017

From graphite-clay composites to graphene electrode materials: In-situ electrochemical oxidation and functionalization

Highlights: • Graphene was synthesized by electrochemical exfoliation of graphite-clay rods with different clay:graphite ratios. • In-situ electrochemical oxidation and functionalization were used in the exfoliated process. • Graphene thin-film electrodes were constructed for supercapacitors and lithium ion batteries. • This work provided a value-added way that can transform the low-purity graphite resources to graphene electrode materials. - Abstract: The development of cost- and time-effective methods to synthesize graphene materials is very urgent in order to promote its large-scale application in electrochemical energy storage devices. Herein, graphene materials were synthesized by the electrochemical exfoliation (electrochemical oxidation) of graphite-clay rods with different clay:graphite ratios in aqueous solution and in short reaction time (1 h). The dual role of electrochemical oxidation reaction was presented: (1) the electrochemical oxidation reaction facilitates the exfoliation of pencil graphite leads and in-situ forms functional groups on graphene; (2) the electrochemical oxidation reaction enhances the Faradaic reaction in supercapacitor. The in-situ electrochemical oxidation and functionalization methods can transform low purity graphite to high-value graphene electrode materials for supercapacitors and lithium ion batteries. The specific capacitances of exfoliated graphene are 20-time larger than that of graphite-clay composites. This work provided a value-added way that can transform the low-purity graphite resources to high performance graphene electrode materials.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Quasi-In-Situ Analysis of Electrode Top Atomic Layers via High-Sensitivity Low-Energy Ion Scattering and Potential-Controlled Sample Transfer

Electrocatalytic reactions involve interfacial interactions between the surfaces of electrodes and reactive species at an electrolyte interface. There are presently no universal or unambiguous methods to directly assay the active top atomic layer composition that influences the reactivity of these electrodes under relevant operating conditions. Low-energy ion scattering (LEIS) spectroscopy is a surface characterization technique that yields compositional analysis of the outermost atomic layer of a material, but it must be performed in ultrahigh vacuum (UHV). Application of LEIS measurements to electrochemical materials that are removed from ambient liquid-phase environments thus leaves an open question as to whether the surface that is transferred to UHV is truly the surface that manifested during the electrochemical reaction. Toward the goal of preserving the active surface state, we developed a sample transfer workflow for LEIS enabling air-free removal and drying of an electrode from an electrochemical cell while maintaining control of the potential using an auxiliary electrode. The potential-controlled emersion method was demonstrated to give distinct potential-dependent surface compositions for a Cu−Pd alloy relative to removal after uncontrolled return to open-circuit potential. A Cu-enriched surface was found at anodic potential and a Pd-enriched surface at cathodic potential, suggesting that the approach can be used to retain representative atomic configurations during transfer. Since adsorbates will often persist from the reaction environment, conventional sample pretreatment methods for removal, including atomic O and atomic H exposure, were also contrasted. Both methods were found to differ with results from incidental low-dose depth profiling by the LEIS primary ion source, which removes adventitious species and surface atoms during the course of repeated measurements. These depth profiles were found to be sensitive to sample history and thus qualitatively informative, despite the possible changes induced by ion damage. The results exhibit (i) the need for complete control over the polarization state of the sample at all times (no excursions to open circuit during transfer) and (ii) the utility of low-dose depth profiling to capture changes in the near-surface composition.

Alloys↗