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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

A Study of Model-Based Protective Fast-Charging and Associated Degradation in Commercial Smartphone Cells: Insights on Cathode Degradation as a Result of Lithium Depositions on the Anode

The ever expanding mobile consumer electronic market has accelerated the need for safe and efficient fast-charging approaches that improve the overall speed of battery charging without hastened deterioration of the battery performance. Herein, the impact of a resource inexpensive, physics-based, electrochemically optimized fast-charging algorithm (charging time < 2 h) for mobile devices is investigated. A critical difference in the amount and morphology of lithium deposits on the anode for cells fast-charged without an optimized algorithm is observed and found to be the main cause of capacity decay. Furthermore, an in-depth study of the LiCoO 2 cathode regions opposite to pronounced lithium deposits on the anode reveals a “mirroring” phenomenon, i.e., a frozen monoclinic phase, and inactivity to relithiation. In operando hard X-ray absorption spectroscopy reveals that degraded spots on harvested cathodes seem to be activated again and participate in the intercalation process when lithiated at low rates from lithium foil counter electrodes. On the other hand, tests at higher C-rates, closer to the actual fast-charging rate, reveal only negligible oxidation state changes and therefore poor performance.

25 ENERGY STORAGE↗
DOE OSTI2022

Elucidating Cathode Degradation Mechanisms in LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811)/Graphite Cells Under Fast Charge Rates Using Operando Synchrotron Characterization

Li-ion batteries capable of extreme fast charging (XFC) are in demand to facilitate widespread electric vehicle (EV) adoption. While the impact of fast charge on the negative electrode has been studied, degradation of state-of-the-art NMC811 under XFC conditions has not been studied in detail. Herein, cathode degradation is probed in NMC811/graphite batteries by analysis of structural and chemical changes for recovered samples previously cycled under XFC conditions and during typical cycling. NMC surface reconstruction, as determined by soft X-ray absorption, was not detected for recovered electrodes. Furthermore, bulk redox activity from X-ray absorption near edge structure measurements showed more change in the oxidation state of Ni and Co under the 1C charge rate compared to the 4C rate consistent with the electrochemistry. Increased unit cell volume contraction under the 1C rate as determined by operando X-ray diffraction suggests that higher charge rates may provide a protective effect on the cathode by reducing structural distortion due to less delithiation.

25 ENERGY STORAGE↗
NASA NTRS1983

Cathode degradation and erosion in high pressure arc discharges

The various processes which control cathode erosion and degradation were identified and evaluated. A direct current arc discharge was established between electrodes in a pressure-controlled gas flow environment. The cathode holder was designed for easy testing of various cathode materials. The anode was a water cooled copper collector electrode. The arc was powered by a dc power supply with current and voltage regulated cross-over control. Nitrogen and argon were used as propellants and the materials used were two percent thoriated tungsten, barium oxide impregnated porous tungsten, pure tungsten and lanthanum hexaboride. The configurations used were cylindrical solid rods, wire bundles supported by hollow molybdenum tubes, cylindrical hollow tubes, and hollow cathodes of the type used in ion thrusters. The results of the mass loss tests in nitrogen indicated that pure tungsten eroded at a rate more than 10 times faster than the rates of the impregnated tungsten materials. It was found that oxygen impurities of less than 0.5 percent in the nitrogen increased the mass loss rate by a factor of 4 over high purity nitrogen. At power levels less than 1 kW, cathode size and current level did not significantly affect the mass loss rate. The hollow cathode was found to be operable in argon and in nitrogen only at pressures below 400 and 200 torr, respectively.

Hardy, T. L.↗
NASA NTRS1984

Cathode degradation and erosion in high pressure arc discharges

The various processes which control cathode erosion and degradation were identified and evaluated. A direct current arc discharge was established between electrodes in a pressure-controlled gas flow environment. The cathode holder was designed for easy testing of various cathode materials. The anode was a water cooled copper collector electrode. The arc was powered by a dc power supply with current and voltage regulated cross-over control. Nitrogen and argon were used as propellants and the materials used were two percent thoriated tungsten, barium oxide impregnated porous tungsten, pure tungsten and lanthanum hexaboride. The configurations used were cylindrical solid rods, wire bundles supported by hollow molybdenum tubes, cylindrical hollow tubes, and hollow cathodes of the type used in ion thrusters. The results of the mass loss tests in nitrogen indicated that pure tungsten eroded at a rate more than 10 times faster than the rates of the impregnated tungsten materials. It was found that oxygen impurities of less than 0.5 percent in the nitrogen increased the mass loss rate by a factor of 4 over high purity nitrogen. At power levels less than 1 kW, cathode size and current level did not significantly affect the mass loss rate. The hollow cathode was found to be operable in argon and in nitrogen only at pressures below 400 and 200 torr, respectively.

Hardy, T. L.↗
DOE OSTI2019

High-Voltage Performance of Ni-Rich NCA Cathodes: Linking Operating Voltage with Cathode Degradation

High-voltage Ni-rich cathodes have been studied as a possible way to achieve high energy density in Li-ion batteries. However, capacity fade due to structural changes at high voltages has limited their applications. In this study, we identify 4.5 V (vs. graphite) as the optimum upper cutoff voltage (UCV) for a Ni-rich NCA cathode [LiNi 0.8 Co 0.15 Al 0.05 O 2 ]. At this UCV, NCA delivers a 12 % increase in reversible capacity (when discharged to 2.5 V) and retains 92 % of its initial capacity after 100 cycles at 1C/-1C cycling when compared to 4.2 V as UCV. By increasing UCV to 4.7 V, the discharge capacity can be raised to >200 mAh/g. However, the rate of capacity fade is greater when compared to 4.5 V as UCV. This increased rate of capacity fade, at higher UCV, is related to irreversible lattice contractions that leads to structural rearrangement at charged states during high-voltage cycling. Lastly, our results show a change in transition metal oxidation states and an onset of structural ordering occurs when the UCV is 4.7 V.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Voltage and temperature effects on low cobalt lithium-ion battery cathode degradation

Degradation of low cobalt lithium-ion cathodes was tested using a full factorial combination of upper cut-off voltage (4.0 V and 4.3 V vs. Li/Li + ) and operating temperature (25 °C and 60 °C). Half-cell batteries were analyzed with electrochemical and microstructural characterization methods. Electrochemical performance was assessed with galvanostatic cycling, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) supported by distribution of relaxation times (DRT) analysis. Electrode microstructure was characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray absorption near edge structure (XANES) imaging. Higher cut-off voltage cycling shows presence of NiO x formation, a low diffusivity rock-salt phase, in both CV and XRD data. XRD patterns confirmed that the rock-salt phase was beginning to form at the low cut-off voltage at high temperature, but in much lower intensity than at the high cut-off voltage. Higher temperature accelerates degradation processes at both voltages. Degradation factors at high temperature include NiO x formation, cathode material dissolution, and electrolyte decomposition. SEM analysis suggests that supporting phases may isolate and disconnect active material particles reducing capacity retention and battery life cycle. DRT analysis and XANES imaging show that both high temperature samples revealed a NiO x phase based on an increased diffusive impedance and a visible shift in the XANES spectra. The low cut-off voltage, high temperature sample showed a split peak and shift to lower energies indicating early formation of the NiO x phase. The diffusive impedance, which hinders intercalation and deintercalation, is driven by the formation of the NiO x phase. While primarily driven by cut-off voltage, elevated temperature also contributes to this degradation mechanism.

electrochemical impedance spectroscopy↗
DOE OSTI2025

Unravelling electro-chemo-mechanical interplay in layered oxide cathode degradation in solid-state batteries

Solid-state batteries (SSBs) hold notable promise for advancing energy storage technologies. However, their commercial viability is limited by the poor cycle stability and complex degradation mechanism. This study underscores the pivotal role of electro-chemo-mechanical interactions in driving the failure of SSBs. Leveraging advanced x-ray imaging and spectroscopy techniques, we analyzed LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) cathodes from cycled Li x In||Li 6 PS 5 Cl (LPSC)||NMC811 SSBs, uncovering the interplay between microstructure, chemical heterogeneity, mechanical characteristics, and electrochemical performance. Our results show that revealing electro-chemo-mechanical interactions is essential to develop strategies to suppress the degradation of SSBs. Particularly, we revisit a LiNbO 3 (LNO) coating layer to mitigate electrochemical degradation. The LNO@NMC811 cathode retains 116 milliampere-hours per gram after 200 cycles, showing excellent stability, while the uncoated NMC811 cathode keeps degrading over time, with suppressed chemical heterogeneity and mechanical failure. This work highlights the importance of synergizing advanced material design with coating techniques, ensuring uniform lithium flux and improving mechanical properties to achieve stable, high-performance SSBs.

Zheng, Xueli [SLAC National Accelerator Laboratory↗
DOE OSTI2022

Coupling of multiscale imaging analysis and computational modeling for understanding thick cathode degradation mechanisms

Here, using a thick NMC811 (LiNi 0.8 Mn 0.1 Co 0.1 O 2 ) electrode as an example, we present a macro- to nanoscale 2D and 3D imaging analysis approach coupled with 4D (space + time) computational modeling to probe its degradation mechanism in a lithium-ion battery cell. Particle cracking increases and contact loss between particles and carbon-binder domain are observed to correlate with the cell degradation. This study unravels that the reaction heterogeneity within the thick cathode caused by the unbalanced electron conduction is the main cause of the battery degradation over cycling. The increased heterogeneity in the system will entail more cathode regions where the degree of active material utilization is uneven, leading to higher probabilities of particle cracking. These findings shed light on the crucial role of the electronic and ionic transportation networks in the performance deterioration of the thick cathode. They also provide guidance for cathode architecture optimization and performance improvement.

25 ENERGY STORAGE↗
DOE OSTI2020

Materials and Approaches for Mitigation of SOFC Cathode Degradation in SOFC Power Systems

Perovskites such as doped lanthanum manganite and cobaltite have been used successfully as a cathode material in SOFC power systems operating between 700-1000°C. The electrodes, however, remain prone to degradation in presence of Cr containing gas atmosphere under systems operating conditions. Cathode in SOFCs is considered as one of the largest contributors of electrochemical performance degradations, leading to significant increase in ohmic and non-ohmic losses as well as interfacial compound formation. These degradations are mostly irreversible due to permanent changes to chemical and morphological alterations in the electrodes, resulting in the blockage of triple phase boundary (TPB) sites and decrease in oxygen reduction reactions (ORR). Fundamental mechanistic understanding has been developed to elucidate the reaction pathways of electrode poisoning in electronically conducting electrodes (LSM) as well as mixed ionic and electronically conducting electrodes (LSCF). The overall goal of this program has been identification and development of cost effective solutions to mitigate electrode degradations under “real world” systems operating conditions. The overall technological innovations and impact from this work are: The research provides an understanding of the degradation mechanism and cost-effective approaches for implementation in SOFC systems; Develop mitigation processes utilizing low cost getters using conventional synthesis and fabrication route; Develop tailored high surface area powders and coatings for high Cr capture capacity under systems operating conditions; >Developed computational models to understand mechanistic behavior; Experimentally measure rate of Cr evaporation from chromia and alumina forming alloys under SOFC operating conditions; Developed conditions to minimize Cr evaporation from balance-of-plant alloys; This innovation will support the development of getter platform to capture both intrinsic and extrinsic impurities present in air; and, Applications under wide operating temperature range (500-900°C) as well for wide high-temperature electrochemical systems (SOFC, SOEC, and OTM). The work has been successfully developed, validated experimentally and implemented. Successful technology transfer of this knowledge with industrial partners has been accomplished and the getters have been independently tested and validated under their systems operating conditions. The innovation will also find application in related high temperature electrochemical systems such as OTM and SOEC for the prevention of Cr assisted performance degradation. The proposed approach for Cr capture can also be applied to oxy-combustion and other advanced combustion techniques for the reduction of Cr vapor in the exhaust gas stream. This fundamental knowledge gained also has led to the path forward for developing advanced getters for capturing more than one contaminant in air.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2022

Concealed Cathode Degradation in Lithium-Ion Cells with a Ni-Rich Oxide

Difficulties with sourcing cobalt and the interest in increasing cell energy have motivated the development of Ni-rich oxide materials for lithium-ion battery cathodes. Despite the intense research on the topic, there is limited information available on the long-term performance of novel cathode formulations. Here, we evaluate the stability of LiNi 0.9 Mn 0.05 Co 0.05 O 2 in full-cells tested for over five months, assessing how cycling, voltage and electrolyte additives impact cathode aging. We use differential voltage analysis to extract insights about the cathode from the full-cell data and identify the isolation of cathode particles in the delithiated (charged) state as a relevant mode of aging. Importantly, this particular mechanism of cathode aging does not cause immediate cell capacity fade, causing the simple analysis of cell capacity retention to overestimate the cathode stability under the investigated conditions. So, our observations serve as cautionary tale indicating that careful analysis of data from extended testing may be required for assessing the performance of Ni-rich cathodes and for evaluating how these materials are affected by electrolyte additives.

25 ENERGY STORAGE↗
DOE OSTI2022

Modeling Chemo-Mechanics with Electrolyte Infiltration to Quantify Degradation of Cathode Particles

One of the main goals in modeling lithium-ion batteries is to improve/predict longevity and resilience of new chemistries. To that end, this talk investigates the formation of stress-induced fracture within polycrystalline cathode particles and the impact on capacity loss. Physically based cathode aging dynamics is simulated in a 3D, continuum-level chemo-mechanical model. The model captures anisotropic Li diffusion within a single polycrystalline particle comprised of hundreds to thousands of randomly oriented grains. A recent addition to this model includes electrolyte infiltration, which occurs when the electrolyte seeps into surface cracks within the particle. The model predicts that particle fracture is primarily due to non-ideal grain interactions with slight dependence on high-rate charge demands. Essentially, when neighboring grains are misaligned, they expand a different rates relative to one another leading to high stresses and ultimately the formation of intraparticle cracks. The model predicts that small particles with large grains develop significantly less damage than larger particles with small grains. Finally, the model predicts most of the chemo-mechanical damage accumulates in the first charge after formation. This chemo-mechanical "damage saturation" effect indicates that initial particle fracture occurs within the first few cycles, while long-term cathode degradation is not solely chemo-mechanically induced. The principle contribution of this research is the use of an anisotropic chemo-mechanical model to test how particle geometry affect capacity fade, which predicts that particle size has a stronger effect on capacity fade than grain size and ultimately that small particles with large grains have the least capacity fade.

cathode↗
DOE OSTI2019

Investigation of LSM-YSZ Composite Cathode Performance Degradation with a Multistep Charge Transfer Model

The long-term performance degradation of LSM/YSZ composite cathodes is investigated via calibrated multiphysics simulation with a multistep oxygen reduction reaction (ORR) model and structural coarsening data from a phase field study. Multiphysics simulations, including a multistep ORR mechanism, are first developed for better understanding of the limiting processes in solid oxide fuel cells. The multistep ORR mechanism includes two parallel pathways, surface pathway and bulk pathway, which consist of elementary reaction steps. The multiphysics model is simultaneously calibrated with experimental polarization curves and impedance behavior for various air/fuel supply conditions. To our knowledge, this is the first time that a multistep ORR model is calibrated with such datasets. Next, the calibrated simulations are utilized to simulate a 2D half-cell constructed with measured microstructural data and random heterogeneity. Finally, the long-term performance degradation of the half-cell is predicted by the calibrated multiphysics model coupled with structural coarsening trends simulated using a phase field-based coarsening model. Degradation of both polarization curves and impedance behavior is investigated. Thorough analyses, including changes of contributions from different pathways, the resistance components, and overall reaction order, are performed to provide more insights into cathode performance degradation due to grain coarsening phenomena.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Understanding Discharge‐Driven Growth of Cathode Impedance in Ni‐Rich NMC Cathodes

Degradation of LiNi x Mn y Co 1-x-y O 2 (NMC)-based lithium-ion batteries depends strongly on cut-off voltage ranges. In addition to the high upper cut-off voltage, a high depth of discharge (i.e., lower cut-off voltage) significantly worsens cathode impedance growth and capacity fade during long-term cycling. However, there is currently no consensus on the mechanism behind the negative role of a deep discharge. Here, this phenomenon was investigated in graphite||NMC cells with single-crystal cathodes (LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NMC622) or LiNi 0.76 Co 0.14 Mn 0.10 O 2 (NMC76)) using targeted aging protocols (constant high-voltage holds vs. charge–discharge cycling), while monitoring transition-metal (TM) dissolution, cathode-electrolyte interface (CEI) impedance, and NMC surface composition. We demonstrate a correlation between discharge-driven CEI impedance growth and increased TM dissolution. Furthermore, this degradation pathway is more pronounced in lower-Ni NMC622 than in higher-Ni (NMC76) under comparable delithiation states at charge, with both compositions undergoing the H2→H3 phase transition. X-ray photoelectron spectroscopy (XPS) reveals NMC composition-dependent evolution of surface lattice oxygen and restructured surface layer composition between charged and discharged states. These findings add mechanistic depth to the role of discharge as an active driver of interfacial degradation and provide new insights into its composition dependence.

25 ENERGY STORAGE↗
DOE OSTI2021

Mitigation of PtCo/C Cathode Catalyst Degradation via Control of Relative Humidity

Maintaining the high performance of proton-exchange membrane fuel cells (PEMFC) over the course of its lifetime is a key enabling factor for its successful commercialization as a primary power source in zero-emission transportation applications. In this context, it is important to mitigate the degradation of PtCo-alloy based cathode catalysts used for oxygen reduction reaction (ORR). PtCo-alloy catalysts exhibit high activity at beginning-of-life (BOL) which tends to decrease during operation due to loss of electrochemical surface area (ECSA) and dissolution-contamination related effects of the Co-alloying component. Here, we demonstrate the use of relative humidity (RH) of the inlet gases as a controllable parameter to mitigate the degradation of PtCo-alloy catalyst degradation. We employ a catalyst-specific voltage cycling accelerated stress test (AST) durability protocol as a function of inlet RH to degrade PtCo catalysts. A series of in situ electrochemical diagnostics and ex situ characterizations have been carried out to investigate the catalyst layer characteristics at end-of-test (EOT). Our results show that at sub-saturated conditions of durability protocol operation, PtCo catalyst sustains higher EOT H 2 /air performance due to better retention of ECSA and smaller impact of Co 2+ dissolution/contamination.

25 ENERGY STORAGE↗