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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 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Microstructure and Mechanical Properties of Intercritically Treated Grade 91 Steel

Premature creep failures at the intercritical heat affected zone (ICHAZ) of creep-resistant steel weldments have been frequently reported. However, the creep degradation mechanism of different microstructure constituents in ICHAZ is complicated and needs further clarification. In this work, Grade 91 steel was intercritically heat-treated at a temperature (860 °C) between the critical temperatures AC1 and AC3, and a correlation between microstructure and mechanical properties of the heat-treated specimen was built. The effects of austenitization and tempering resulting from the intercritical treatment (IT) differentiated the local strain energies between the two microstructure constituents: newly transformed martensite (NTM) and over-tempered martensite (OTM). The formation of NTM grains led to a hardness increase from 247 HV0.5 in the base metal to 332 HV0.5 in the IT specimen. The ultimate tensile strength (UTS) increased from 739 MPa in the base metal to 1054 MPa in the IT specimen. Extensive growth of the OTM grains and rapid recovery of NTM grains took place simultaneously in the IT specimen during a typical tempering at 760 °C. These microstructure degradations led to a lowered hardness of 178 HV0.5, a reduced UTS of 596 MPa, and a poor creep resistance with a minimum creep strain rate of 0.49 %/h at 650 °C in an IT + tempering (ITT) specimen.

36 MATERIALS SCIENCE↗
NASA NTRS1983

A simulation investigation of the effects of engine-and thrust-response characteristics on helicopter handling qualities

A multi-phase program is being conducted to study, in a generic sense and through ground simulation, the effects of engine response, rotor inertia, rpm control, excess power, and vertical damping on specific maneuvers included in nap-of-the-Earth (NOE) operations. The helicopter configuration with an rpm-governed gas-turbine engine are considered. Handling-qualities-criteria data are considered in light of aspects peculiar to rotary-wing and NOE operations. The results of three moving-based piloted simulation studies are summarized and the frequency, characteristics of the helicopter thrust response which set it apart from other VTOL types are explained. Power-system response is affected by both the engine-governor response and the level of rotor inertia. However, results indicate that with unlimited power, variations in engine response can have a significant effect on pilot rating, whereas changes in rotor inertia, in general, do not. The results also show that any pilot interaction required to maintain proper control can significantly degrade handling qualities. Data for variations in vertical damping and collective sensitivity are compared with existing handling-qualities specifications, MIL-F-83300 and AGARD 577, and show a need for higher minimums for both damping and sensitivity for the bob-up task. Results for cases of limited power are also shown.

Corless, L. D.↗
NASA NTRS1982

Digital TV tri-state delta modulation system for Space Shuttle ku-band downlink

A tri-state delta modulation/demodulation (TSDM) technique which provides for efficient run-length coding of constant-intensity segments of a TV picture is described. Aspects of the hardware implementation of a high-speed TSDM transmitter and receiver for black-and-white TV or field-sequential color or NTSC format color are reviewed. Run-length encoding of the TSDM output can consistently reduce the required channel data rate well below one bit per sample. As compared with a bistate delta modulation system, the present technique eliminates granularity in the reconstructed video without degrading rise or fall times. About 40 chips are used by TSDM when used to handle the luminance information in a color link. A possible overall space and ground functional configuration to accommodate Shuttle digital TV with scrambling for privacy is presented.

Udalov, S.↗
NASA NTRS1991

A hybrid LBG/lattice vector quantizer for high quality image coding

It is well known that a vector quantizer is an efficient coder offering a good trade-off between quantization distortion and bit rate. The performance of a vector quantizer asymptotically approaches the optimum bound with increasing dimensionality. A vector quantized image suffers from the following types of degradations: (1) edge regions in the coded image contain staircase effects, (2) quasi-constant or slowly varying regions suffer from contouring effects, and (3) textured regions lose details and suffer from granular noise. All three of these degradations are due to the finite size of the code book, the distortion measures used in the design, and due to the finite training procedure involved in the construction of the code book. In this paper, we present an adaptive technique which attempts to ameliorate the edge distortion and contouring effects.

Ramamoorthy, V.↗
NASA NTRS2008

The impact of hydrogen contamination on the Total Dose Response of Linear Bipolar Microcircuits

Recent enhanced low dose rate sensitivity (ELDRS) investigations carried out by RLP Research, Crane, Arizona State University (ASU), and Jet Propulsion Laboratory (JPL) have shown significant differences in the degradation of bipolar microcircuits with total dose in the presence of molecular hydrogen (H2) in packages. This has a significant impact on radiation hardness assurance and opens up opportunity to improve device performance. The objectives of this program are 1) to investigate and confirm the causal relationship between packaging recipes, hydrogen contamination, and total dose response of linear bipolar microcircuits; and 2) to develop a guideline that will take into account these effects at the radiation level for future NASA space missions. This program is geared to benefit all future NASA space missions using bipolar or BiCMOS linear devices.

McClure, Steve S.↗
NASA NTRS2023

Survival of Juvenile Florida Scrub-Jays is Habitat Specific, Positively Correlated With Month and Negatively Correlated With Male Breeder Death

Juvenile survival in birds is difficult to estimate but this vital rate can be an important consideration for management decisions. We estimated juvenile survival of cooperatively breeding Florida Scrub-Jays (Aphelocoma coerulescens) in a landscape degraded by fire suppression and fragmentation using data from marked (n = 325) and unmarked juveniles (n = 1,306) with an integrated hierarchical Bayesian model. To assess the combined analyses, we also analyzed these datasets separately, with a Cormack-Jolly-Seber (CJS) model (marked) and young model (unmarked). Our data consisted of monthly censuses of territorial family groups from Florida Scrub-Jay populations in East Central Florida collected over a 22-yr period. Juvenile survival was estimated from July when young Florida Scrub-Jays begin developing independence to March when they become first year individuals and grouped according to the habitat quality class of their natal territory that were based on shrub height (with intermediate shrub heights being optimal and short and tall shrub heights being suboptimal) and the presence of sandy openings (the preferred open having many sandy openings; closed not having enough). Parameter estimates in the combined analysis were intermediate to the separate analyses. Notable differences among the separate analyses were that suboptimal habitat survival was lower in the unmarked analysis, the unmarked analysis showed a linear effect of time not seen in the marked analysis, and there was an effect of male breeder death in the marked but not unmarked analysis. The combined data analysis provided more inference than did either data set analyzed separately including juveniles in optimal-closed territories unexpectedly had higher survival than those in optimal-open, survival increased through time, and male breeder death had a negative effect on survival. This study suggests that optimal-closed habitat may play an important role in juvenile Florida Scrub-Jay survival perhaps by providing better cover from predators and warrants further investigation for management implications.

Florida Scrub-Jay↗
DOE OSTI2021

Optimal Sizing of an Electric Vehicle Charging Station with Integration of PV and Energy Storage

This paper proposes an optimization model for the optimal configuration of an grid-connected electric vehicle (EV) extreme fast charging station considering integration of photovoltaic (PV) and energy storage. The proposed model minimizes the annualized net cost (i.e., maximizes the annualized net profit) of the extreme fast charging station, including investment and maintenance cost of charging ports, PV and energy storage, net cost of purchasing energy from utility and selling energy to EV customers, degradation cost of energy storage and demand charge. The decision variables are number of charging ports, capacity of invested PV and the power and energy ratings of invested energy storage. The Erlang-loss system is adopted to model the EV mobility. Results of numerical simulations indicate that investment of PV and energy storage could increase the annualized profit of the extreme fast charging station. In addition, the impacts of various parameters on the optimal solution are investigated by sensitivity analysis.

Liu, Guodong↗
NASA NTRSDate not supplied

Thermo-Poro-Mechanical Modeling of RTV Intumescence

Room temperature vulcanizing (RTV) silicone is a high-temperature adhesive used as a gap-filler between heatshield tiles in numerous entry missions. Its propensity to intumesce, or swell upon exposure to heat, is a well-known effect that needs to be carefully quantified during design. At tile interfaces of charring ablators, intumescence, combined with differential recession, could cause the gap filler to protrude past the ablator outer mold line, forming a “fence”. Fencing can in turn cause transition to turbulence of the flow wetting the heat shield, leading to augmented surface heating. Recent experiments conducted at the Plasmatron X facility, the high enthalpy wind tunnel of the Center for Hypersonics and Entry Systems Studies, have shown prominent fencing of RTV gap fillers in PICA, under both nitrogen and air plasmas. Similar observations are well known in the arcjet literature. Further experiments under controlled environment, performed using in situ X-ray micro-computed tomography (micro-CT) at the Advanced Light Source (ALS), have shown heating rate-dependent swelling and shrinkage of RTV during pyrolysis. To simulate RTV intumescence, a novel model was introduced in the Porous Materials Analysis Toolbox based on OpenFOAM, PATO, to account for pore-pressure buildup within both closed- and open-pores. The governing equation for the thermo-poro-mechanical response were developed, assuming linear elasticity for the charring silicone. A new multi-pyrolysis model that tracks non-monotonic advancement of material properties with pyrolysis was proposed. This model addresses the limitations of state-of-the-art ablator models to capture the different stages of thermal degradation and coupled thermomechanics. Swelling of RTV was simulated using the new thermo-poro-mechanical model and compared against in situ micro-CT data. Results showed good agreement in intumescence height and temperature profiles at all heating rates, indicating that the key factor contributing to RTV swelling is the internal pressure build-up within closed- and open-pores. As RTV is cured into a soft (rubbery) compound with low-porosity and permeability, initial temperature increase and pyrolysis gas production cause a significant increase of internal pressure, causing a pronounced volume growth. As thermal degradation progresses, rigidization of the silicone occurs due to char hardening which counteract volume shrinkage after gas pressure relief. Overall, our model shows that accounting for changes in properties such porosity, permeability and key thermomechanical coefficients is crucial for capturing the RTV volume change during ablation and enable a predictive capability for heatshield tile interface response. A plan for future calibration of thermomechanical properties evolution during degradation is discussed, as a key next step to close the new model.

RTV↗
NASA NTRSDate not supplied

Thermo-Poro-Mechanical Modeling of RTV Intumescence

Room temperature vulcanizing (RTV) silicone is a high-temperature adhesive used as a gap-filler between heatshield tiles in numerous entry missions. Its propensity to intumesce, or swell upon exposure to heat, is a well-known effect that needs to be carefully quantified during design. At tile interfaces of charring ablators, intumescence, combined with differential recession, could cause the gap filler to protrude past the ablator outer mold line, forming a “fence”. Fencing can in turn cause transition to turbulence of the flow wetting the heat shield, leading to augmented surface heating. Recent experiments conducted at the Plasmatron X facility, the high enthalpy wind tunnel of the Center for Hypersonics and Entry Systems Studies, have shown prominent fencing of RTV gap fillers in PICA, under both nitrogen and air plasmas. Similar observations are well known in the arcjet literature. Further experiments under controlled environment, performed using in situ X-ray micro-computed tomography (micro-CT) at the Advanced Light Source (ALS), have shown heating rate-dependent swelling and shrinkage of RTV during pyrolysis. To simulate RTV intumescence, a novel model was introduced in the Porous Materials Analysis Toolbox based on OpenFOAM, PATO, to account for pore-pressure buildup within both closed- and open-pores. The governing equation for the thermo-poro-mechanical response were developed, assuming linear elasticity for the charring silicone. A new multi-pyrolysis model that tracks non-monotonic advancement of material properties with pyrolysis was proposed. This model addresses the limitations of state-of-the-art ablator models to capture the different stages of thermal degradation and coupled thermomechanics. Swelling of RTV was simulated using the new thermo-poro-mechanical model and compared against in situ micro-CT data. Results showed good agreement in intumescence height and temperature profiles at all heating rates, indicating that the key factor contributing to RTV swelling is the internal pressure build-up within closed- and open-pores. As RTV is cured into a soft (rubbery) compound with low-porosity and permeability, initial temperature increase and pyrolysis gas production cause a significant increase of internal pressure, causing a pronounced volume growth. As thermal degradation progresses, rigidization of the silicone occurs due to char hardening which counteract volume shrinkage after gas pressure relief. Overall, our model shows that accounting for changes in properties such porosity, permeability and key thermomechanical coefficients is crucial for capturing the RTV volume change during ablation and enable a predictive capability for heatshield tile interface response. A plan for future calibration of thermomechanical properties evolution during degradation is discussed, as a key next step to close the new model.

silicone intumescence↗
DOE OSTI2026

Confinement Reconstruction Unlocks Stable Ru Single Atom-Doped IrO x Anodes for Long-Term High-Rate CO 2 Electrolysis

IrO 2 is a commonly employed anode catalyst for CO 2 electrolysis in membrane electrode assembly (MEA) systems. However, under high current densities, its structural reconstruction leads to activity loss and stability degradation, limiting the industrial viability of CO 2 electrolysis. In this work, we demonstrated a confinement reconstruction strategy to precisely regulate the structural evolution during electrolysis. Ethylene glycol serves as a structural modulator, protecting the catalyst surface, suppressing soluble species formation, and promoting ordered structural evolution. Single-atom Ru acts as a stability enhancer, forming robust Ir–O–Ru bridging structures that facilitate an ordered transformation from a 4-fold [RuO 4 ]/[IrO 4 ] to a 6-fold symmetry [RuO 6 ]/[IrO 6 ] octahedral framework, thereby enhancing structural rigidity and long-term stability. As a result, in MEA-based CO 2 electrolysis, the catalyst achieves a stable operation at 200 mA cm –2 for 480 h, maintaining a CO selectivity above 80%. Theoretical calculations further elucidate that the enhanced stability originates from the suppression of oxygen vacancy formation, making the lattice-oxygen-mediated mechanism (LOM) potentially less favorable. This work provides insights into the structural evolution of the OER catalysts under high-current-density conditions, paving the way for large-scale CO 2 electrolysis commercialization.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1984

A performability solution method for degradable nonrepairable systems

The present performability model-solving algorithm identifies performance with 'reward', representing the state behavior of a system S by a finite-state stochastic process and determining reward by means of reward rates that are associated with the states of the base model. A general method is obtained for determining the probability distribution function of the performance (reward) variable, and therefore the performability, of the corresponding system. This is done for bounded utilization periods, and the result is an integral expression which is either analytically or numerically solvable.

Furchtgott, D. G.↗
DOE OSTI2020

Beneficial Effect of Li 5 FeO 4 Lithium Source for Li-Ion Batteries with a Layered NMC Cathode and Si Anode

The energy density of lithium-ion batteries can be increased by replacing the traditional graphite anode with a high capacity silicon anode. However, volume changes and interfacial instabilities cause a large irreversible capacity and a continual loss of lithium during cycling, which lead to rapid capacity loss. In this work, we add Li 5 FeO 4 (LFO) to a LiNi 0.5 Mn 0.3 Co 0.2 O 2 (NMC) cathode as a pre-lithiation additive, which increases the lithium inventory and extends the cycle life of Si-graphite/NMC full cells, and decreases the NMC particle degradation. LFO delivers a large 764 mAh g –1 LFO capacity below 4.7 V vs Li/Li + . By tuning the LFO content in Si-graphite/LFO-NMC full cells, we show higher capacity, improved retention, lower impedance, and superior rate performance compared to full cells without LFO. Post-test characterizations demonstrate that LFO inclusion in the cathode matrix leads to less NMC secondary particle segregation/cracking and a thinner surface reduced layer on the NMC particles. The beneficial effects of LFO endure after the lithium reserve has been exhausted, highlighting a lasting synergy between the lithium source and electrode active materials. This study introduces a new approach to simultaneously increase lithium inventory and reduce cathode degradation, and makes critical advances toward enabling Si anodes for lithium-ion batteries.

25 ENERGY STORAGE↗
NASA NTRS2003

Investigation of Dynamic Oxygen Adsorption in Molten Solder Jetting Technology

Surface tension forces play a critical role in fluid dynamic phenomena that are important in materials processing. The surface tension of liquid metals has been shown to be very susceptible to small amounts of adsorbed oxygen. Consequently, the kinetics of oxygen adsorption can influence the capillary breakup of liquid-metal jets targeted for use in electronics assembly applications, where low-melting-point metals (such as tin-containing solders) are utilized as an attachment material for mounting of electronic components to substrates. By interpreting values of surface tension measured at various surface ages, adsorption and diffusion rates of oxygen on the surface of the melt can be estimated. This research program investigates the adsorption kinetics of oxygen on the surface of an atomizing molten-metal jet. A novel oscillating capillary jet method has been developed for the measurement of dynamic surface tension of liquids, and in particular, metal melts which are susceptible to rapid surface degradation caused by oxygen adsorption. The experimental technique captures the evolution of jet swells and necks continuously along the jet propagation axis and is used in conjunction with an existing linear, axisymmetric, constant-property model to determine the variation of the instability growth rate, and, in turn, surface tension of the liquid as a function of surface age measured from the exit orifice. The conditions investigated so far focus on a time window of 2-4ms from the jet orifice. The surface properties of the eutectic 63%Sn-37%Pb solder alloy have been investigated in terms of their variation due to O2 adsorption from a N2 atmosphere containing controlled amounts of oxygen (from 8 ppm to 1000 ppm). The method performed well for situations where the oxygen adsorption was low in that time window. The value of surface tension for the 63Sn-37Pb solder in pure nitrogen was found to be 0.49 N/m, in good agreement with previously published work. A characteristic time of O(1ms) or less was determined for the molten-metal surface to be saturated by oxygen at 1000 ppm concentration in N2.

Megaridis, Constantine M.↗
NASA NTRS1996

Use of CCSDS and OSI Protocols on the Advanced Communications Technology Satellite

Although ACTS (Advanced Communications Technology Satellite) provides an almost error-free channel during much of the day and under most conditions, there are times when it is not suitable for reliably error-free data communications when operating in the uncoded mode. Because coded operation is not always available to every earth station, measures must be taken in the end system to maintain adequate throughput when transferring data under adverse conditions. The most effective approach that we tested to improve performance was the addition of an 'outer' Reed-Solomon code through use of CCSDS (Consultative Committee for Space Data Systems) GOS 2 (a forward error correcting code). This addition can benefit all users of an ACTS channel including those applications that do not require totally reliable transport, but it is somewhat expensive because additional hardware is needed. Although we could not characterize the link noise statistically (it appeared to resemble uncorrelated white noise, the type that block codes are least effective in correcting), we did find that CCSDS GOS 2 gave an essentially error-free link at BER's (bit error rate) as high as 6x10(exp -4). For users that demand reliable transport, an ARQ (Automatic Repeat Queuing) protocol such as TCP (Transmission Control Protocol) or TP4 (Transport Protocol, Class 4) will probably be used. In this category, it comes as no surprise that the best choice of the protocol suites tested over ACTS was TP4 using CCSDS GOS 2. TP4 behaves very well over an error-free link which GOS 2 provides up to a point. Without forward error correction, however, TP4 service begins to degrade in the 10(exp -7)-10(exp -6) range and by 4x10(exp -6), it barely gives any throughput at all. If Congestion Avoidance is used in TP4, the degradation is even more pronounced. Fortunately, as demonstrated here, this effect can be more than compensated for by choosing the Selective Acknowledgment option. In fact, this option can enable TP4 to deliver some throughput at error rates as high as 10(exp -5).

Chirieleison, Don↗
DOE OSTI2020

Investigating the Chemical Reactivity of Lithium Silicate Model SEI Layers

Silicon anodes suffer from an unstable solid electrolyte interphase (SEI) layer that contributes to undesirable capacity fade with cycling. A key part to addressing this unstable SEI formation is to examine how certain components of the SEI react with the electrolyte over time. One SEI component that has not been thoroughly studied in the context of the chemical reactivity against the electrolyte is lithiated silicate. Four model silicate thin films with increasing lithium content were deposited by radio frequency (RF) magnetron sputtering to study how the lithiation of the native oxide on a silicon anode affects the chemical stability of the anode surface. SiO2, Li2Si2O5, Li2SiO3, and Li3SiOx films were exposed to 1.2 M LiPF6 in the 3:7 wt% ethylene carbonate/ethyl methyl carbonate (EC/EMC) electrolyte for periods of time that are representative of the amount of time it takes to undergo cell formations. Soaked samples were rinsed, dried, and characterized by a combination of attenuated total reflectance-infrared spectroscopy (ATR-IR), focused ion beam-secondary electron microscopy (FIB-SEM), and X-ray photoelectron spectroscopy (XPS) depth profiling. It was found that the rate of the decrease in film thickness of the silicates exposed to the electrolyte over time increases as a function of the lithium content in the thin film. This reaction involves HF etching and LiPF6 salt degradation leading to silicate loss and fluorination throughout the bulk. Understanding this chemical instability is critical to determining the overall mechanism of SEI degradation over time.

ADVANCED PROPULSION SYSTEMS,ENERGY STORAGE↗
DOE OSTI2021

Evolutionary innovations through gain and loss of genes in the ectomycorrhizal Boletales

Summary We aimed to identify genomic traits of transitions to ectomycorrhizal ecology within the Boletales by comparing the genomes of 21 symbiotrophic species with their saprotrophic brown‐rot relatives. Gene duplication rate is constant along the backbone of Boletales phylogeny with large loss events in several lineages, while gene family expansion sharply increased in the late Miocene, mostly in the Boletaceae. Ectomycorrhizal Boletales have a reduced set of plant cell‐wall‐degrading enzymes (PCWDEs) compared with their brown‐rot relatives. However, the various lineages retain distinct sets of PCWDEs, suggesting that, over their evolutionary history, symbiotic Boletales have become functionally diverse. A smaller PCWDE repertoire was found in Sclerodermatineae. The gene repertoire of several lignocellulose oxidoreductases (e.g. laccases) is similar in brown‐rot and ectomycorrhizal species, suggesting that symbiotic Boletales are capable of mild lignocellulose decomposition. Transposable element (TE) proliferation contributed to the higher evolutionary rate of genes encoding effector‐like small secreted proteins, proteases, and lipases. On the other hand, we showed that the loss of secreted CAZymes was not related to TE activity but to DNA decay. This study provides novel insights on our understanding of the mechanisms influencing the evolutionary diversification of symbiotic boletes.

Wu, Gang↗
DOE OSTI2020

Concurrently Approaching Volumetric and Specific Capacity Limits of Lithium Battery Cathodes via Conformal Pickering Emulsion Graphene Coatings

Abstract To achieve the high energy densities demanded by emerging technologies, lithium battery electrodes need to approach the volumetric and specific capacity limits of their electrochemically active constituents, which requires minimization of the inactive components of the electrode. However, a reduction in the percentage of inactive conductive additives limits charge transport within the battery electrode, which results in compromised electrochemical performance. Here, an electrode design that achieves efficient electron and lithium‐ion transport kinetics at exceptionally low conductive additive levels and industrially relevant active material areal loadings is introduced. Using a scalable Pickering emulsion approach, Ni‐rich LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) cathode powders are conformally coated using only 0.5 wt% of solution‐processed graphene, resulting in an electrical conductivity that is comparable to 5 wt% carbon black. Moreover, the conformal graphene coating mitigates degradation at the cathode surface, thus providing improved electrochemical cycle life. The morphology of the electrodes also facilitates rapid lithium‐ion transport kinetics, which provides superlative rate capability. Overall, this electrode design concurrently approaches theoretical volumetric and specific capacity limits without tradeoffs in cycle life, rate capability, or active material areal loading.

Park, Kyu‐Young↗
DOE OSTI2023

Mastering the synergy between Na 3 V 2 (PO 4 ) 2 F 3 electrode and electrolyte: A must for Na-ion cells

Sodium-ion batteries are emerging as suitable energy storage devices for special applications such as high-power devices with the advantages of being cheaper and more sustainable than the Li-ion equivalents. The sodium ion cells consisting of polyanionic Na 3 V 2 (PO 4 ) 2 F 3 - hard carbon electrodes exhibit high power rate capabilities but limited cycle life, especially at high temperatures. To circumvent this drawback we herein conducted in-depth analyses of the origins of structural degradations occurring in Na 3 V 2 (PO 4 ) 2 F 3 electrodes upon long cycling. Vanadium dissolution with associated parasitic reactions is identified as one of the major reasons for cell failure. Its amount varies depending on the electrolyte, with NaTFSI-based electrolyte showing the least vanadium dissolution as the TFSI - anion decomposes without producing acidic impurities, in contrast to the NaPF 6 -based electrolyte. The dissolved vanadium species undergoes oxidation and reduction processes at the Na 3 V 2 (PO 4 ) 2 F 3 and HC electrodes, respectively, with the electrochemical signature of these processes being used as a fingerprint to identify state of health of the 18650 cells. Here, having found that surface reactivity is the primary cause of vanadium dissolution we provide methods to mitigate it by combining surface coating and optimized electrolyte formulation.

25 ENERGY STORAGE↗