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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

High energy density picoliter-scale zinc-air microbatteries for colloidal robotics

The recent interest in microscopic autonomous systems, including microrobots, colloidal state machines, and smart dust, has created a need for microscale energy storage and harvesting. However, macroscopic materials for energy storage have noted incompatibilities with microfabrication techniques, creating substantial challenges to realizing microscale energy systems. Here, we photolithographically patterned a microscale zinc/platinum/SU-8 system to generate the highest energy density microbattery at the picoliter (10 −12 liter) scale. The device scavenges ambient or solution-dissolved oxygen for a zinc oxidation reaction, achieving an energy density ranging from 760 to 1070 watt-hours per liter at scales below 100 micrometers lateral and 2 micrometers thickness in size. The parallel nature of photolithography processes allows 10,000 devices per wafer to be released into solution as colloids with energy stored on board. Within a volume of only 2 picoliters each, these primary microbatteries can deliver open circuit voltages of 1.05 ± 0.12 volts, with total energies ranging from 5.5 ± 0.3 to 7.7 ± 1.0 microjoules and a maximum power near 2.7 nanowatts. We demonstrated that such systems can reliably power a micrometer-sized memristor circuit, providing access to nonvolatile memory. We also cycled power to drive the reversible bending of microscale bimorph actuators at 0.05 hertz for mechanical functions of colloidal robots. Additional capabilities, such as powering two distinct nanosensor types and a clock circuit, were also demonstrated. The high energy density, low volume, and simple configuration promise the mass fabrication and adoption of such picoliter zinc-air batteries for micrometer-scale, colloidal robotics with autonomous functions.

Robotics↗
DOE OSTI2023

Exploring Proton Activity at the Membrane/Electrode Interface with Microelectrodes

Microelectrode measurements using a polycrystalline platinum microelectrode were used to simulate the membrane/electrode interface of a membrane-electrode-assembly (MEA) architecture. The proton activity for the hydrogen-evolution reaction (HER) was evaluated for 40, 60, and 80% relative humidity. Proton activity was calculated to be 0.5, 1.0 and 2.0 for 40, 60, and 80% relative humidity, respectively, using open circuit potential measurements between Nafion 211 and 1 molal HClO 4 . The fraction of protons which dissociate at a given relative humidity condition appears to be a distinctive factor in proton activity for Nafion 211 compared to an aqueous electrolyte. In conclusion, the microelectrode measurements exhibited a Tafel slope of ~120 mV/dec, similar to that observed for platinum in MEA systems, demonstrating that kinetic measurements made with microelectrodes can be representative of MEA kinetics.

Anderson, Grace C.↗
DOE OSTI2020

Communication—Dissolution and Passivation of a Ni-Cr-Fe-Ru-Mo-W High Entropy Alloy by Elementally Resolved Electrochemistry

The formation and dissolution of the passive film on a novel NiCrFeRuMoW high entropy alloy in H 2 SO 4 was measured with atomic emission spectroelectrochemistry. Passivation involved Cr and Ru enrichment, whether passivation was achieved spontaneously at open circuit or by potentiostatic step into the passive domain. The other elements, Ni, Fe, Mo, and W, dissolved at rates approximately proportional to their bulk concentrations. The air formed film showed only a Cr enrichment. Excellent corrosion resistance properties were indicated by spontaneous passivation, the low passive current in the polarization curve, and the absence of detectable elemental dissolution during the active peak.

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

A Nitroxide Containing Organic Molecule in a Deep Eutectic Solvent for Flow Battery Applications

The nitroxide radical redox organic molecule, 2-phenyl-4,4,5,5-tetrame- thylimidazoline-1-oxyl-3-oxide (PTIO), was investigated for the first time in a deep eutectic solvent (DES)-like system consisting of a 1:4 molar ratio of choline chloride and ethylene glycol(Ch1EG4) as a redox flow battery electrolyte. PTIO is a single molecule with three oxidation states, and can provide both positive and negative redox couples for a flow battery. A flow battery using the PTIO/Ch1EG4 electrolyte demonstrated nearly 50% roundtrip efficiency with an approximately 1 V open circuit potential. Inefficiencies were primarily due to membrane resistance which can be significantly lowered with increased temperature. While PTIO appears stable over short periods (hours), the oxidized form is not stable in the DES-like electrolyte over longer times. Molecular modeling was performed to investigate the relative stability of PTIO in DES as compared to the previously studied 4-hydroxy-TEMPO (4HT). It was found that the oxoammonium cation 4HT + exhibits a noticeably larger nucleophilic reactive cloud as compared to PTIO + , indicating a higher reactivity. This method to predict stability of the oxoammonium cation shows promise to inform the design and synthesis of promising redox systems based on nitroxide radicals in DES electrolytes to identify new chemistries for large scale energy storage.

25 ENERGY STORAGE↗
DOE OSTI2021

Flow Injection Electrochemical Quartz Crystal Microbalance with ICP-OES Detection: Recovery of Silver by Electrodeposition with Redox Replacement in a Flow Cell

We developed a new on-line hyphenated flow injection analysis technique (FI-EQCM-ICP-OES) that allows electrochemical deposition and stripping with mass detection and elemental analysis. This technique was used to study a new system for electrochemical recovery of silver from a 0.5 mM Ag + /5 mM Cu 2+ /0.5 M H 2 SO 4 solution by pulsed electrodeposition with redox replacement (EDRR) in a small flow cell. The metal ions in a 500 μ l sample are injected into the sulfuric acid carrier stream and deposited onto an electrochemical quartz crystal microbalance (EQCM) electrode housed in a 50 μ l flow cell. The deposits are subsequently stripped off electrochemically in the same cell and analyzed downstream in an ICP-OES. The stripped metal layer was found to be composed of Ag with no detectable Cu for a redox replacement time of 10 s, and 91 wt.% Ag–9 wt.% Cu for a redox replacement time of 5 s. Microscopy measurements demonstrated that the electrode was covered with silver particles, some of which contain Cu in the case of the 5 s replacement time. This technique allowed the study of mass changes on the electrode during electrodeposition and open circuit times in each EDRR cycle in flowing solutions.

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

Electrochemical and In Situ Spectroscopic Study of the Effect of Prussian Blue as a Mediator in a Solid-State Supercapacitor

In situ X-ray absorption spectroscopy (XAS) along with electrochemical measurements were used to explore the redox activity of Prussian blue (PB) and its contribution to pseudocapacitance in an asymmetrical solid-state supercapacitor (SC). The SC, with a configuration of (activated carbon)/polymer electrolyte membrane/(activated carbon + PB), was fabricated with an embedded KCl saturated Ag/AgCl reference electrode. The potentials of the two electrodes were generally displaced proportionally with increase in the cell voltage. Upon negative polarization from the open circuit voltage (OCV) condition to -3 V, the charge capacity was greater than that upon positive polarization from the OCV condition to +3 V, in agreement with the higher fraction of Fe(III) than that of Fe(II) and the low concentration of K ions in PB. Detailed analysis of cyclic voltammetry data in the range between 0 and -3 V indicates that the battery-like contribution to the charge current was 96% that of the capacitor-like contribution at a scanning rate of 2.5 mV s -1 but only 15% at 100 mV s -1 . The in situ XAS characterization results indicate that the majority of Fe was reversibly charged and discharged between Fe(III) and Fe(II) during positive and negative polarizations with minimal changes in local atomic structure.

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

Adsorption Processes during Electrochemical Atomic Layer Deposition of Gold

Electrochemical atomic layer deposition (e-ALD) technique offers a simple and effective "wet chemistry" approach enabling high-precision monolayer-by-monolayer deposition of metal films. The process of e-ALD of Au involves lead underpotential deposition (PbUPD) followed by its redox replacement by a Au monolayer. The time evolution of the deposit mass during "one-pot" Au e-ALD is known to exhibit a unique three-stage response that is presently not well understood. In this work, we probe this response using voltammetry, electrochemical quartz crystal microgravimetry (e-QCM), and chronoamperometry to unravel the underlying mechanistic events during Au e-ALD. Furthermore, the presence of adsorbed Au +3 -ligand complex(es) (Au-L) on the Au surface is established. In stage I of e-ALD, this Au-L adsorbed layer is reduced to Au while a Pb UPD adlayer is formed. In stage II, the Pb UPD adlayer undergoes spontaneous surface-limited redox replacement by nobler Au under open-circuit conditions. Finally, in stage III, re-adsorption of the Au-L occurs on the newly deposited Au. Quantitative analysis of the deposit mass transients obtained under a variety of conditions provides an estimate of the Au-L mass and its molecular weight.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Time-Resolved X-ray Operando Observations of Lithiation Gradients across the Cathode Matrix and Individual Oxide Particles during Fast Cycling of a Li-Ion Cell

Lithiated transition metal oxides serve as active materials in the positive electrode (cathode) of lithium-ion cells. During electrochemical cycling, lithium ions intercalate and deintercalate into these oxide particles. This behavior causes two types of lithiation gradients to emerge: (i) a bulk gradient across the depth of the cathode matrix (averaged over individual oxide particles) and (ii) a microscopic gradient across the particles themselves, which also depends on their location in the electrode. Here we show how both gradients can be studied using operando X-ray diffraction during 4C charge and 4C discharge. The oxide (de)lithiation is estimated from the unit cell parameters by indexing the X-ray diffraction spectra. By fitting the lithiation profiles with orthogonal polynomials, the bulk gradients across the electrode thickness are quantified. These gradients develop as the current flows through the cell and dissipate during open-circuit and potentiostatic-hold periods. Further details of lithiation dynamics can be obtained through shape analysis of the Bragg peaks. In particular, from electrochemical model simulations, we show that the width and skewness of the (003) peak track (de)lithiation fronts moving across the individual oxide particles.

(003) peak↗
DOE OSTI2022

Electrochemical Modeling and Experimental Verification of Lithiation Gradients in Oxide Cathodes of Lithium-Ion Cells

Lithiated nickel-cobalt-manganese oxides, such as NCM523, are used in the positive electrode (cathode) of Li-ion cells. Using operando X-ray diffraction profilometry, lithiation gradients in the cathode matrix can be observed and quantified by expansion into Legendre polynomials with time-dependent weights. These weights (referred to as gradients) increase in magnitude when electric current flows through the cell, decrease during potentiostatic hold and finally relax to zero when the current is interrupted during open circuit rest. Both physics-based electrochemical models and operando X-ray experiments suggest that the time constants for gradient growth and abatement are primarily determined by ionic diffusion in the oxide particles, which in turn depends on their lithium content. In contrast, the magnitude of gradients depends mainly on the applied current. The X-ray profilometry provides a way of directly probing the formation and disappearance of Li gradients across the cathode during fast cycling, which can help to diagnose the effects of material degradation in the cells.

25 ENERGY STORAGE↗
DOE OSTI2022

Analytical and Numerical Analysis of Lithium Plating Onset in Single and Bilayer Graphite Electrodes during Fast Charging

Lithium plating is commonly observed in anodes charged at fast rates, and can lead to capacity loss and battery safety issues. The increased risk of plating has been attributed to transport limitations, and architectured electrodes may reduce plating risk. However, while theoretical studies have shown that reaction non-uniformity arises due to interplay of transport limitations, anode open circuit voltage behavior and reaction kinetics, its effect on lithium plating has not been studied. We use analytic and numerical simulations to predict onset of plating in graphite anode half-cells at high C-rates and demonstrate how anodes with layered porosities can delay plating. Simplified analytical models identify trends for plating onset and predictions are calibrated against numerical models. A calibrated numerical model of graphite demonstrates qualitative agreement with analytical model predictions. This reaction inhomogeneity mechanism occurs in the absence of lithium ion depletion, indicating that these mechanisms may contribute to capacity loss independently or simultaneously. A bilayer model of graphite exhibits delayed plating onset, and an optimization procedure is presented. This theoretical work presents quantitative and mechanistic insight on how reaction inhomogenity affects lithium metal plating onset and can be used as a guide to engineer anodes resistant to lithium plating.

Mijailovic, Aleksandar S.↗
DOE OSTI2022

The Poor Academic’s DC-Offset for Reversing Polarity in Electrochemical Cells: Application to Redox Flow Cells

We provide a simple and inexpensive manual DC-offset method for extending the accepted voltage range of a battery cycler to negative voltages, without interfering with the actual operation of the electrochemical cell under the test or exceeding the voltage specs of the battery cycler instrument. We describe the working principles of the method and validate the proposed setup by operating short-term and long-term redox flow battery cycling using compositionally symmetric cell, with open-circuit voltage of zero, and full cell configurations. The method can be used to extend the capability of battery cycler instrumentation to operate any electrochemical cell that requires the polarity to be reversed during operation. Applications include cycling of other symmetric cells (e.g., Li-ion cells), implementation of polarity reversal steps for rejuvenation of electroactive species or rebalancing electrochemical cells, and alternating polarity for electrochemical synthesis.

25 ENERGY STORAGE↗
DOE OSTI2023

Improved Fuel Cell Chemical Durability of an Heteropoly Acid Functionalized Perfluorinated Terpolymer-Perfluorosulfonic Acid Composite Membrane

Commercial proton exchange membrane heavy-duty fuel cell vehicles will require a five-fold increase in durability compared to current state-of-the art light-duty fuel cell vehicles. We describe a new composite membrane that incorporates silicotungstic heteroply acid (HPA), α -K 8 SiW 11 O 40 ▪13H 2 O, a radical decomposition catalyst and when acid-exchanged can potentially conduct protons. The HPA was covalently bound to a terpolymer of tetrafluoroethylene, vinylidene fluoride, and sulfonyl fluoride containing monomer (1,1,2,2,3,3,4,4-octafluoro-4-((1,2,2-trifluorovinyl)oxy)butane-1-sulfonyl fluoride) by dehydrofluorination followed by addition of diethyl (4-hydroxyphenyl) phosphonate, giving a perfluorosulfonic acid-vinylidene fluoride-heteropoly acid (PFSA-VDF-HPA). A composite membrane was fabricated using a blend of the PFSA-VDF-HPA and the 800EW 3M perfluoro sulfonic acid polymer. The bottom liner-side of the membrane tended to have a higher proportion of HPA moieties compared to the air-side as gravity caused the higher mass density PFSA-VDF-HPA to settle. The composite membrane was shown to have less swelling, more hydrophobic properties, and higher crystallinity than the pure PFSA membrane. The proton conductivity of the membrane was 0.130 ± 0.03 S cm −1 at 80 °C and 95% RH. Impressively, when the membrane with HPA-rich side was facing the anode, the membrane survived more than 800 h under accelerated stress test conditions of open-circuit voltage, 90 °C and 30% RH.

08 HYDROGEN↗
DOE OSTI2023

Electrochemical Deposition with Redox Replacement of Lanthanum with Uranium in Molten LiCl-KCl

Electrochemical recovery of dilute concentrations of actinides from spent nuclear fuel would reduce the longevity of storing high-level nuclear waste. Electrochemical deposition with redox replacement (EDRR) is used in a molten salt medium for the selective electrochemical recovery of uranium in the presence of excess concentrations of lanthanum. In each EDRR cycle, after a short electrodeposition pulse, the deposited lanthanum is spontaneously replaced by uranium at open circuit. After repeated cycles, uranium metal was obtained on a tungsten electrode immersed in LiCl-KCl melt that contained 1 wt.% lanthanum chloride – 0.15 wt.% uranium 4+ chloride. Here, scanning electron microscopy and energy dispersive X-ray spectroscopy analysis revealed uranium particles approximately 0.5 - 1 μm with well-defined rectangular shapes; and with 20 – 60 times more uranium recovered on the surface of the electrode than lanthanum.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2023

Long-Term Stability of Mullite and Magnesia-encased Ag|Ag + Reference Electrodes in Molten MgCl 2 -KCl-NaCl

In this study, the stability of Ag|Ag + molten chloride reference electrodes was studied using mullite and magnesia tubes as reference electrode membrane materials in molten MgCl 2 -KCl-NaCl for continuous immersion up to 31 d. Two electrochemical methods were used to characterize the long-term performance of the reference electrodes at 500 °C in an inert atmosphere using a Mg rod as the working electrode: open circuit potential (OCP) and onset of Mg(II) reduction as measured by cyclic voltammetry (CV). There was only a 3% difference between the average OCP measured versus the mullite and MgO reference electrodes. Potential drift was higher for mullite (−1.34 mV d −1 ) than MgO (0.22 mV d −1 ). But both drift rates were very low compared to the OCP data standard deviation, indicating that no significant drift was measured for us to 31 d.

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

Isothermal Microcalorimetric Analysis of Li/CF x Battery Discharge

Lithium/carbon monofluoride (Li/CF x ) batteries generate substantial amounts of heat during discharge in part due to the large deviation of the loaded voltage from the measured and thermodynamically predicted open circuit voltage. Here, in this study, we further analyze this system by estimating the equilibrium voltage (V eq ) and its temperature dependence (dV eq /dT) over the entire discharge range. Based on these results, the ohmic and entropic heat contributions to the overall heat flow are calculated from experimental data. The ohmic heat flow is consistent with an electrochemical impedance spectroscopy model and electrode density measurements, indicating decreasing porosity of the electrode during discharge. Entropic heating increases during discharge as the cell reaction becomes increasingly entropically unfavorable. The total energy dissipated by the cell (electrical and thermal) remains similar over the entire discharge, evidence for a two-phase reaction with a constant, and rate-independent, ΔG rxn of about -465 kJ mol -1 . However, near the end of discharge (>90% DOD), ΔG rxn changes significantly indicating possible secondary reactions.

25 ENERGY STORAGE↗
DOE OSTI2023

Ni/NiO Reference Electrode Potential Measurements in Molten CaCl 2 –CaO

A direct oxide reduction (DOR) process is used to reduce PuO 2 to Pu metal via Ca metal. Molten CaCl 2 is commonly used as the electrolyte for this reaction. As the DOR reaction proceeds, CaO accumulates in the salt and must be measured in real-time to know when the reaction has gone to completion. Open circuit potential (OCP) was measured in this report between a reference electrode consisting of Ni/NiO contained in a MgO tube and a tungsten working electrode. Two methods of CaO additions were performed over several experiments, and both methods correlated to a 0.11 to 0.23 V decrease in OCP up to 14.4 wt% CaO. CaO concentrations were separately measured via sampling and acid-base titration. A plot of OCP versus concentration of CaO fits the Nernst equation with the CaO powder additions up to 5.2 wt% and also at the higher end of the CaO pellet concentration range. While the MgO tubes were observed to be structurally stable in the molten salt, scanning electron microscopy and energy dispersive X-ray spectroscopy showed that Mg in the tubes had been partially replaced with Ca.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Effect of Metal Chloride Impurities on Equilibrium Potential of Fe/FeCl 2 in Eutectic LiCl-KCl

In this study, interaction of dilute metal chloride solutes in molten eutectic LiCl-KCl was studied via equilibrium potential measurements. Open circuit potential (OCP) was measured between a pure iron rod and a Ag/AgCl reference electrode with concentration of FeCl 2 varying from 0.2–1 mol% at 530 °C. The Nernst equation was used to calculate activity coefficient of FeCl 2 based on OCP. Measurements were made in LiCl-KCl-FeCl 2 with and without additions of 0.5 mol% CsCl, NaCl, and LaCl 3 . The activity coefficient of FeCl 2 was found to be unaffected by these small concentrations of CsCl, LaCl 3 , and NaCl. However, there was observed evidence that the activity coefficient of FeCl 2 , above 0.8 mol% Fe, may be affected by the presence of LaCl 3 at higher concentrations beginning around 0.5 mol% La. Over the full range of conditions tested, the activity coefficient of FeCl 2 in molten LiCl-KCl ranged from 2.95 × 10 −5 to 1.01 × 10 −4 .

Electrochemistry↗
DOE OSTI2023

Simulation of Impedance Changes with Aging in Lithium Titanate-based Cells Using Physics-Based Dimensionless Modeling

Quantifying aging effects in lithium-ion cells with chemistries that have a flat open circuit potential is challenging. We implement a physics-based electrochemical model to track changes in the electrochemical impedance response of lithium titanate-based cells. Frequency domain equations of a pseudo two-dimensional model are made dimensionless, and the corresponding non-dimensional parameters are estimated using a Levenberg-Marquardt routine. The model weighs the relative contributions of changes in diffusion, ionic conduction within the electrolyte phase against solid phase electronic conduction towards cell aging. Solid-phase diffusion, charge transfer resistance and double layer capacitance at the solid-liquid interface are accounted for in the particle impedance. The estimation routine tracks dimensionless parameters using accelerated cycling data from full cells over 1000 cycles. The model can be deployed within a short time for state estimation using physics-based models without requiring prior knowledge of the battery chemistry, format, or capacity.

25 ENERGY STORAGE↗