Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Lattice oxygen redox”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Halting Oxygen Evolution to Achieve Long Cycle Life in Sodium Layered Cathodes

Oxygen redox chemistries at high voltage have materialized as a revolutionary paradigm for cathodes with high-energy density; however, they are plagued by the challenges of labile oxygen loss and rapid degradations upon cycling, even after concerted endeavors from the research community. Here we propose a multi-concentration stratagem propelled by entropy reinforcement to enhance the electronic structure disorder (ESD) at high desodiation states for impeding undesired oxygen mobility and ensuring controlled oxygen activity, elucidated by density functional theory calculations. The increased disorder strengthens the reversible electrochemistry of lattice oxygen redox, leading to effectively suppressed P−O structural evolution and highly stable localized TMO 6 octahedral environments, as demonstrated by soft/hard X-ray absorption spectroscopy. Furthermore, through a comparative analysis of sodium-layered cathodes with different configuration entropy, we reveal that a high-entropy state induced by cationic disordering has the capacity to perturb cationic redox boundaries, significantly restraining the formation of detrimental O′3 phases. As a consequence, the high-voltage cycling stability has been greatly upgraded, up to 4.4 V versus Na + /Na, with an impressive 90.1 % capacity retention at 1 C over 100 cycles and 76.1 % capacity retention at 2 C over 300 cycles. In conclusion, the resilient oxygen redox, enabled through the control of ESD, broadens the horizons for entropy engineering and lays the foundation for advancements in high-energy, long-cycling, and safe batteries.

25 ENERGY STORAGE↗
DOE OSTI2026

Complex-Concentrated Anion Doping Enables Ultra-Stable Lattice Oxygen and Structural Integrity in Lithium-Rich Layered Oxide Cathodes

Lithium- and manganese-rich layered oxides (LMR) stand out as next-generation lithium-ion cathode chemistries, which harness both transition-metal and lattice-oxygen redox processes to deliver exceptional capacity and energy density. However, their full potential is hindered by intrinsic oxygen instability and structural degradation, resulting in pronounced voltage fade and capacity decay. Here, we present a complex-concentrated anion-doping paradigm in which multiple anions, F, Br, and S, are incorporated into the oxygen sublattice to enhance oxygen-redox and structural stability. X-ray absorption spectroscopy and aberration-corrected scanning transmission electron microscopy confirm ultra-stable local oxygen coordination environments during long-term cycling, with detrimental phase transformations and oxygen-loss-induced cavitation dramatically inhibited. Notably, we show that the characteristic LiTM6 transition metal (TM) honeycomb ordering is preserved even after electrochemical cycling. Concurrently, this strategy yields an unprecedented volume change of only 0.63% upon charging to 4.8 V vs. Li+/Li, achieving the first zero-strain LMR cathode. The resulting LMR cathode delivers ultralow voltage fade (1 mV per cycle during the first 100 cycles and becomes negligible in subsequent cycles) and outstanding energy retention (93% after 200 cycles) in a pouch cell configuration. Our complex-concentrated anion-doping concept establishes a broadly applicable strategy for resolving chemo-mechanical failure mechanisms in ceramic intercalation electrodes for next-generation energy storage.

Li-ion batteries↗
DOE OSTI2022

Correlation of Oxygen Anion Redox Activity to In‐Plane Honeycomb Cation Ordering in Na x Ni y Mn 1− y O 2 Cathodes

Sodium‐ion batteries (SIBs) are one of the most promising next‐generation energy storage systems because of their abundant and low‐cost component materials. However, the lower energy density of SIBs compared with lithium‐ion batteries diminishes their practical value proposition. Among the many sodium‐based cathodes, layered transition metal oxides with high sodium content have energy densities comparable with the lithium‐ion battery technology. When charged above 4.1 V, the sodium‐based cathodes often undergo transformations because the activation of oxygen anion redox causes irreversible oxygen release, transition metal ion migration, lattice distortion, and rapid capacity decay. Here, in situ gas analysis is performed to evaluate the lattice oxygen anion redox activity in Na x Ni y Mn 1− y O 2 cathodes with P2 and O3 structural orderings. Operando X‐ray diffraction and neutron diffraction are performed to assess the structural changes related to lattice oxygen redox and transition metal ion migration in Na x Ni y Mn 1− y O 2 cathodes. The results unveil that in‐plane honeycomb cationic ordering can help suppress oxygen anion redox activity, which is critical for the future design of layered transition metal oxide cathodes that are prone to achieve high‐energy for durable SIBs.

25 ENERGY STORAGE↗
DOE OSTI2020

Negligible voltage hysteresis with strong anionic redox in conventional battery electrode

Lattice anionic (oxygen) redox reactions (ARR) offers opportunities for developing high-capacity batteries, however, often suffers the notoriously high hysteresis in voltages and low initial coulombic efficiency. Particularly, ARR was widely considered inherent to these kinetic issues. Here, unambiguous evidences of strong and reversible ARR is found in Na 2/3 Ni 1/3 Mn 2/3 O 2 through mapping of resonant inelastic X-ray scattering (mRIXS). Strikingly, the material displays negligible voltage hysteresis (0.1 V) and high initial coulombic efficiency with a highly stable electrochemical profile. Our independent analysis of the Ni, Mn and O states consistently interpret the redox mechanism of Na 2/3 Ni 1/3 Mn 2/3 O 2 , which reveals a strong ARR system with facile kinetics and highly stable electrochemical profile that previously found only in cationic redox systems of conventional non-Alkali-rich materials.

25 ENERGY STORAGE↗
DOE OSTI2023

Realizing High Capacity and Zero Strain in Layered Oxide Cathodes via Lithium Dual-Site Substitution for Sodium-Ion Batteries

Sodium-ion batteries have garnered unprecedented attention as an electrochemical energy storage technology, but it remains challenging to design high-energy-density cathode materials with low structural strain during the dynamic (de)sodiation processes. In this paper, we report a P2-layered lithium dual-site-substituted Na 0.7 Li 0.03 [Mg 0.15 Li 0.07 Mn 0.75 ]O 2 (NMLMO) cathode material, in which Li ions occupy both transition-metal (TM) and alkali-metal (AM) sites. The combination of theoretical calculations and experimental characterizations reveals that Li TM creates Na–O–Li electronic configurations to boost the capacity derived from the oxygen anionic redox, while Li AM serves as LiO 6 prismatic pillars to stabilize the layered structure through suppressing the detrimental phase transitions. As a result, NMLMO delivers a high specific capacity of 266 mAh g –1 and simultaneously exhibits the nearly zero-strain characteristic within a wide voltage range of 1.5–4.6 V. Our findings highlight the effective way of dual-site substitution to break the capacity–stability trade-off in cathode materials for advanced rechargeable batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Correlating the phase evolution and anionic redox in Co-Free Ni-Rich layered oxide cathodes

Current trend of high-capacity Ni-rich layered cathode is to develop high-Ni and low-Co or Co-free oxides. The high Ni content layered oxides provide great advantages in capacity, cost and environmental benignity, similar to LiNiO 2 parent compound. But they also inherit drawbacks in structural and chemical instability at high voltages upon cycling. As such, elemental substitution plays a profound role in addressing these challenges. This work elucidates the roles of Al doping in cationic redox and anionic oxygen activity in LiAl x Ni 1-x O 2 using combined X-ray absorption spectroscopy (XAS), resonant inelastic X-ray scattering (RIXS) as well as operando differential electrochemical mass spectrometry (DEMS). Using synchrotron wide-angle X-ray scattering (WAXS), we extrapolate a general principle of phase transition and its coupling with lattice anionic oxygen redox. These findings shed light on the advancement of high-capacity, stable-cycling and safe-operating Ni-rich cathode materials for next generation Li-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2022

Building interface bonding and shield for stable Li-rich Mn-based oxide cathode

Implementation of Li-rich Mn-based oxide cathode with high-energy-density has been restrained by capacity/voltage degradation that results from irreversible lattice oxygen loss and structure rearrangements. To resolve these challenges, in this work, Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 encapsulated by amorphous Co x B (CB-LRM) is rationally designed via autocatalytic plating for highly reversible cationic/anionic hybrid cathode material. Band coherency is ingeniously evoked by interface-reconstruction between bulk structure and amorphous coating layer, which lower the energy of O $2p$ states. Furthermore, this is associated with strengthened orbital hybridization of O $2p$-Mn $3d$ and increased formation energy of oxygen vacancy, which mitigates the lattice oxygen loss considerably. Additionally, interface shielding effects that protect electrode against electrolyte corrosion and the reduction of surface oxygen are also present with fully coverage of amorphous Co x B coating layer. As a result, the as-designed CBLRM cathode exhibits excellent cycle stability after 100 loops with only 0.154% per cycle capacity fade and improved voltage degradation. Given this, this work provides a potential avenue for rational design of lattice oxygen-based electrode materials with high-energy-density.

25 ENERGY STORAGE↗
DOE OSTI2021

Utilizing Oxygen Redox in Layered Cathode Materials from Multiscale Perspective

We report in high-capacity layered oxide cathode materials, utilization of lattice oxygen as a redox center is considered to be one of the most promising approaches to overcome the capacity limitation set by conventional transition metal redox centers. However, rapid material degradation is often associated with oxygen oxidation, leading to formidable challenges in utilizing oxygen redox. Further mechanistic understanding of the oxygen activities thus becomes critical to better control oxygen redox reactions. This review summarizes recent advances for investigating oxygen redox reactions in cathode materials from a multiscale perspective, i.e., from the atomistic level to the microstructure regime. First the mechanistic aspects of oxygen redox and the consequences of this reaction on various electrode degradation pathways during battery operation (e.g., oxygen loss, transition metal migration, irreversible phase transition), relating structural changes at the crystallographic scale to those at the macro scale, are discussed. Then recent developments based on atomic and microstructure modifications that are promising for improving the reversibility of oxygen redox reaction or mitigating the harmful processes arising from oxidation of the oxygen centers under high operating voltage are recounted. The analysis is concluded with a commentary on further research directions toward optimizing the oxygen activity for high-capacity charge storage.

25 ENERGY STORAGE↗
DOE OSTI2025

A Quasi-Ordered Mn-Rich Cathode with Highly Reversible Oxygen Anion Redox Chemistry

Anionic oxygen redox chemistry in Li-rich Mn-based layer oxide cathodes represents a transformative approach for boosting the energy density of next-generation lithium-ion batteries. However, conventional oxygen redox reactions often induce oxygen dimerization at high voltages, leading to irreversible lattice oxygen loss and a rapid voltage fade. Herein, we achieve highly reversible oxygen redox chemistry through a new quasi-ordered structural design that incorporates both intra- and interlayer cation disorder configurations. This unique structure significantly enhances lattice oxygen stability, effectively stabilizes oxidized oxygen, and inhibits the formation of peroxo- or superoxol-like species, thereby enabling anionic redox reactions to proceed reversibly even at deep delithiation states. The quasi-ordered design mitigates irreversible phase transitions and preserves the structural integrity throughout extended cycling. Consequently, the proposed cathode demonstrates exceptional cyclability with negligible capacity and voltage fade, retaining 99% capacity and 98% average voltage after long-term cycling. Finally this work provides fresh insights into addressing issues related to lattice oxygen instabilities and reforming strategies for developing long-life, high-energy-density anionic redox cathode materials for advanced batteries.

chemical structure↗
DOE OSTI2025

Mesoporous Amorphous High-Entropy Oxide Films: Unlocking Enhanced Redox Activity

High-entropy oxides (HEOs) represent a frontier in catalyst design via entropy-stabilized solid solution formation. However, their catalytic efficiency is limited by their bulk and dense nature. This work presents a strategic approach to tackle this challenge by fabricating mesoporous amorphous HEO films (MA-HEOF) possessing maximized active site utilization efficiency. The success hinges on the as-developed geometric engineering strategy via controlled deposition–precipitation to confine the amorphous HEO thin film on the surface of mesoporous channels. The unique structure of MA-HEOF was elucidated via microscopy-, X-ray-, and neutron-based techniques, which were manifested by enriched surface-activated lattice oxygen and enhanced redox activity, as confirmed by isotope studies. Besides, the MA-HEOF could stabilize and modulate the properties of integrated noble metal sites, enhancing their redox activity in diverse reactions. In conclusion, the approaches and insights presented herein provide guidance on maximizing the utilization efficiency of high-entropy materials in catalysis and beyond.

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

Impacts of Solvent Washing on the Electrochemical Remediation of Commercial End-of-Life Cathodes

Changes to surface structure and chemistry occurring throughout the functional lifetime of lithium-ion batteries (LIBs) may impact the effectiveness of end-of-life rejuvenation methods. Solvent washing prior to electrochemical relithiation is shown to both increase relithiation efficacy and beneficially alter the interfacial chemistry of heavily degraded industrial cathode material. Four common solvents (acetone, diethyl carbonate, isopropyl alcohol, propylene carbonate) are employed to investigate the role of varying physicochemical solvent properties on the mechanism of capacity recovery. Electrochemical (dQ/dV, EIS), structural (XRD), and chemical (SPME-GC-MS) analysis techniques are employed to comprehensively analyze solvent-cathode interactions. Highly nucleophilic solvents (acetone, DEC) are found to reduce cathode charge-transfer impedance and enable stable impedance growth throughout subsequent cycling. The use of nucleophilic solvents under mechanically aggressive washing conditions may also enable the reintroduction of bulk lattice oxygen, thereby restoring anionic redox capacity. Further, the four solvents are found to selectively remove a subset of surface species from the aged cathode material, including residual electrolyte, additives, and electrolyte-additive reaction products, which are qualitatively analyzed. Surface species removal by each solvent is correlated with the electrochemical performance of the correspondingly washed cathode, highlighting the importance of an optimized washing protocol to effective remediation in the context of direct LIB recycling. For the material under study, the use of a simple acetone washing protocol prior to electrochemical relithiation enables up to 174% capacity recovery relative to unwashed/relithiated black mass.

ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2025

Oscillatory redox behavior in oxides: Cyclic surface reconstruction and reactivity modulation via the Mars–van Krevelen mechanism

The breaking of translational symmetry at oxide surfaces gives rise to coordinatively unsaturated cations/anions and surface restructuring—key factors that govern surface reactivity. Using direct in situ environmental transmission electron microscopy (TEM) observations along with atomistic modeling, we report oscillatory redox behavior in CuO under H 2 , where cyclic surface reconstruction and reactivity modulation occur via the Mars–van Krevelen (MvK) mechanism. We observe self-switching between oxygen-rich and oxygen-deficient surface reconstructions, alternately activating and deactivating the surface for H 2 O formation. During periods of chemical inactivity, the oxygen-deficient surface undergoes slow reoxidation via lattice oxygen diffusing from subsurface and bulk reservoirs, restoring the active oxygen-rich surface termination. The inherent disparity in chemical activity among undercoordinated surface ions, along with sluggish subsurface-to-surface oxygen replenishment, drives this oscillatory redox cycle, modulating H2-induced loss of lattice oxygen at the surface and its delayed replenishment from the subsurface. This creates spatiotemporally separated redox steps at the oxide surface. The phenomena and atomistic insights presented here have significant implications for manipulating the surface reactivity of oxides by tuning the separation of these redox steps.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Quantitative Decoupling of Oxygen-Redox and Manganese-Redox Voltage Hysteresis in a Cation-Disordered Rock Salt Cathode

Pronounced voltage hysteresis in Li-excess cathode materials is commonly thought to be associated with oxygen redox. However, these materials often possess overlapping oxygen and transition-metal redox, whose contributions to hysteresis between charge and discharge are challenging to distinguish. In this work, a two-step aqueous redox titration is developed with the aid of mass spectrometry (MS) to quantify oxidized lattice oxygen and Mn 3+/4+ redox in a representative Li-excess cation-disordered rock salt—Li 1.2 Mn 0.4 Ti 0.4 O 2 (LMTO). Two MS-countable gas molecules evolve from two separate titrant-analyte reactions, thereby allowing Mn and O redox capacities to be decoupled. The decoupled O and Mn redox coulombic efficiencies are close to 100% for the LMTO cathode, indicating high charge-compensation reversibility. As incremental Mn and O redox capacities are quantitatively decoupled, each redox voltage hysteresis is further evaluated. Overall, LMTO voltage hysteresis arises not only from an intrinsic charge-discharge voltage mismatch related to O redox, but also from asymmetric Mn-redox overvoltages. The results reveal that O and Mn redox both contribute substantially to voltage hysteresis. In conclusion, this work further shows the potential of designing new analytical workflows to experimentally quantify key properties, even in a disordered material having complex local coordination environments.

25 ENERGY STORAGE↗
DOE OSTI2024

Cationic and Anionic Redox of Battery Cathodes Investigated by Advanced Synchrotron‐Based Mapping of Resonant Inelastic X‐ray Scattering

Abstract Redox reaction builds the foundation stone for the energy density of rechargeable battery cathodes. Probing and understanding the redox reaction behavior is crucial, but also extremely formidable, which requires individual and reliable detection of cationic and anionic redox states. Fortunately, the recently developed ultra‐high‐efficiency mapping of resonant inelastic X‐ray scattering (mRIXS) has emerged as a powerful tool to probe the battery chemistry states. Here, the latest advances of employing advanced mRIXS is summarized to investigate the cationic and anionic redox mechanism of battery cathodes during electrochemical operation. Owing to the new dimension of information along the emission energy and high sensitivity to valence 3d states, 3d transition‐metal L ‐edge (TM‐ L ) mRIXS can eliminate the lineshape distortion in conventional 3d TM‐ L fluorescence X‐ray absorption spectra and investigate the cationic redox quantitatively. Moreover, O‐ K mRIXS could fingerprint the intrinsic oxidized lattice oxygen states and quantify the oxygen redox (OR) reversibility, thus demystifying the controversy in traditional wisdom. In addition, different modification strategies coupled with underlying mechanisms for regulating the activity and reversibility of OR utilizing mRIXS are also summarized. This review provides valuable guidance for further exploration of underlying reaction mechanisms of battery cathodes by mRIXS, along with both technological and scientific improvements.

Cheng, Chen↗
DOE OSTI2022

In Situ Monitoring of H 2 -Induced Nonstoichiometry in Cu 2 O

Nonstoichiometry plays a pivotal role in the functioning of oxide materials, but it is challenging to measure the non-stoichiometric formation and the resulting charge redistribution around the point defects. Using ambient-pressure X-ray photoelectron spectroscopy and Auger electron spectroscopy to monitor the reduction of Cu 2 O in H 2 , we identify the formation of an intermediate, oxygen-deficient Cu 2 O phase and its progressive inward growth into the deeper region of the oxide. Complemented by DFT modeling, we show that the oxygen-deficient Cu 2 O formation occurs via molecular H 2 adsorption at the Cu 2 O surface, which results in the loss of lattice O from the formation of H 2 O molecules that desorb spontaneously from the oxide surface. The resulting oxy-gen-deficient Cu 2 O is a stable intermediate that persists before the Cu 2 O is fully reduced to metallic Cu. The O vacancy induced charge redistribution of the coordinating Cu atoms results in a satellite feature in Cu LMM, which can be used a fingerprint to identify the nonstoichiometry and local charge transfer in non-stoichiometric oxides.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Oxygen redox activities governing high-voltage charging reversibility of Ni-rich layered cathodes

A schematic illustration indicative of the improved structural reversibility through stabilizing oxidized oxygen by Al doping. The chemical reactions and phase transitions at high voltages are generally considered to determine the electrochemical properties of high-voltage layered cathodes such as Ni-rich rhombohedral oxides. Even if significantly higher SOCs (states-of-charge) are utilized above the capability of transition metal redox (primarily Ni and Co), the effect of oxygen redox on Ni-rich rhombohedral oxides still looks mysterious thereby necessitating research that can clarify the relationship between redox reactions and phase transitions. Here, we performed a comprehensive and comparative study of the cationic and anionic redox reactions, as well as the structural evolution of a series of commercial Ni-rich layered oxides with and without Al doping. We combined the results from X-ray spectroscopy, operando electrochemical mass spectrometry, and neutron diffraction with electrochemical properties and thereby revealed the different oxygen redox activities associated with structural and electrochemical degradations. We reveal that Al doping suppresses the irreversible oxygen release but enhances the lattice oxygen oxidization. With this modulated oxygen redox activity, the Ni-rich layered oxides’ notorious H2–H3 structural phase transition becomes highly reversible. Our findings disentangle the different oxygen redox activities during high-voltage cycling and clarify the role of dopants in the Ni-rich layered oxides in terms of structural and electrochemical stability, shedding light on the future direction of optimizing layered cathode materials for safer high energy-density secondary batteries.

Lee, Gi-Hyeok↗