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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 OSTI2023

Comprehensively Strengthened Metal‐Oxygen Bonds for Reversible Anionic Redox Reaction

Introducing anionic redox in layered oxides is an effective approach to breaking the capacity limit of conventional cationic redox. However, the anionic redox reaction generally suffers from excessive oxidation of lattice oxygen to O 2 and O 2 release, resulting in local structural deterioration and rapid capacity/voltage decay. Here, a Na 0.71 Li 0.22 Al 0.05 Mn 0.73 O 2 (NLAM) cathode material is developed by introducing Al 3+ into the transition metal (TM) sites. Thanks to the strong Al–O bonding strength and small Al 3+ radius, the TMO 2 skeleton and the holistic TM–O bonds in NLAM are comprehensively strengthened, which inhibits the excessive lattice oxygen oxidation. The obtained NLAM exhibits a high reversible capacity of 194.4 mAh g —1 at 20 mA g —1 and decent cyclability with 98.6% capacity retention over 200 cycles at 200 mA g —1 . In situ characterizations reveal that the NLAM experiences phase transitions with an intermediate OP4 phase during the charge–discharge. Theoretical calculations further confirm that the Al substitution strategy is beneficial for improving the overlap between Mn 3d and O 2p orbitals. Importantly, this finding sheds light on the design of layered oxide cathodes with highly reversible anionic redox for sodium storage.

25 ENERGY STORAGE↗
DOE OSTI2025

Transition metal vacancy and position engineering enables reversible anionic redox reaction for sodium storage

Triggering the anionic redox reaction is an effective approach to boost the capacity of layered transition metal (TM) oxides. However, the irreversible oxygen release and structural deterioration at high voltage remain conundrums. Herein, a strategy for Mg ion and vacancy dual doping with partial TM ions pinned in the Na layers is developed to improve both the reversibility of anionic redox reaction and structural stability of layered oxides. Both the Mg ions and vacancies (□) are contained in the TM layers, while partial Mn ions (~1.1%) occupy the Na-sites. The introduced Mg ions combined with vacancies not only create abundant nonbonding O 2p orbitals in favor of high oxygen redox capacity, but also suppress the voltage decay originated from Na–O–□ configuration. The Mn ions pinned in the Na layers act as “rivets” to restrain the slab gliding at extreme de-sodiated state and thereby inhibit the generation of cracks. The positive electrode, Na 0.67 Mn 0.011 [Mg 0.1 □ 0.07 Mn 0.83 ]O 2 , delivers an enhanced discharge capacity and decent cyclability. This study provides insights into the construction of stable layered oxide positive electrode with highly reversible anionic redox reaction for sodium storage.

Cai, Congcong [Wuhan Univ. of Technology (China)]↗
DOE OSTI2021

Anionic redox reaction triggered by trivalent Al 3+ in P3-Na 0.65 Mn 0.5 Al 0.5 O 2

P3-Na 0.65 Mn 0.5 Al 0.5 O 2 (NMAO) has been synthesized and studied as a cathode for sodium batteries, and shows anionic redox reaction (ARR) and exhibits a first charging capacity of ~110 mA h g -1 . The electrochemical mechanism of NMAO was comprehensively investigated by X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and density functional theory (DFT) calculations. The reversible oxygen redox behaviour is triggered by Al 3+ through oxygen quasi non-bonding states generated by the relatively ionic interaction of Al and O. Furthermore, the presence of Al 3+ can suppress oxygen loss in ARR. Overall, this work provides new insights into the design and mechanism of anionic redox active cathode materials.

25 ENERGY STORAGE↗
DOE OSTI2024

Moderate active Fe 3+ doping enables improved cationic and anionic redox reactions for wide-voltage-range sodium storage

Layered metal oxides are promising cathode materials for sodium-ion batteries (SIBs) due to their high theoretical specific capacity and wide Na + diffusion channels. However, the irreversible phase transitions and cationic/anionic redoxes cause fast capacity decay. Herein, P2-type Na 0.67 Mg 0.1 Mn 0.8 Fe 0.1 O 2 (NMMF-1) cathode material with moderate active Fe 3+ doping has been designed for sodium storage. Uneven Mn 3+ /Mn 4+ distribution is observed in NMMF-1 and the introduction of Fe 3+ is beneficial for reducing the Mn 3+ contents both at the surface and in the bulk to alleviate the Jahn–Teller effect. The moderate Fe 3+ /Fe 4+ redox can realize the best tradeoff between capacity and cyclability. Therefore, the NMMF-1 demonstrates a high capacity (174.7 mAh g -1 at 20 mA g -1 ) and improved cyclability (78.5% over 100 cycles) in a wide-voltage range of 1.5–4.5 V (vs. Na + /Na). In-situ X-ray diffraction reveals a complete solid-solution reaction with a small volume change of 1.7% during charge/discharge processes and the charge compensation is disclosed in detail. This study will provide new insights into designing high-capacity and stable layered oxide cathode materials for SIBs.

25 ENERGY STORAGE↗
DOE OSTI2024

An Na/TM-site Mg substituted P2-Na 2/3 [Fe 1/3 Mg 1/12 Mn 7/12 ]O 2 cathode with extremely high capacity for sodium-ion batteries

The anionic redox reaction (ARR) has become a hot topic in battery research due to its ability to provide high energy density. Nevertheless, there are still many issues in Na-based layered oxides with the ARR, such as large voltage hysteresis, lattice oxygen loss, irreversible structural changes, and cation migration in the TM layer, resulting in structural collapse and poor electrochemical performance. Herein, a series of Na 2/3 [Fe 1/3 Mg x Mn 2/3–x ]O 2 cathodes are synthesized using a traditional solid-state reaction method. The effectiveness of Mg substitution amounts and site occupancy in regulating the reversibility of the ARR has been explored using various experimental techniques. Surprisingly, the well-designed Na/TM-site Mg substituted P2-Na 2/3 [Fe 1/3 Mg 1/12 Mn 7/12 ]O 2 exhibits an extremely high initial reversible capacity of ~253.21 mA h g –1 , equivalent to ~0.94 e – transfer, which is contributed by both cationic and anionic redox reactions as confirmed by hard X-ray absorption spectroscopy (hXAS) and soft X-ray absorption spectroscopy (sXAS) analyses. In addition, the improved cycling and high-rate performance of the P2-Na 2/3 [Fe 1/3 Mg 1/12 Mn 7/12 ]O 2 are achieved by a well-maintained crystal structure and the highly reversible anionic redox reaction of O 2– /O n– . Finally, these in-depth studies provide crucial knowledge for the development and understanding of cathode materials with a highly reversible ARR for low-cost and high-energy sodium-ion batteries.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Reversible Anionic Redox Activities in Conventional LiNi 1/3 Co 1/3 Mn 1/3 O 2 Cathodes

Redox reactions of oxygen have been considered critical in controlling the electrochemical properties of lithium-excessive layered-oxide electrodes. However, conventional electrode materials without overlithiation remain the most practical. Typically, cationic redox reactions are believed to dominate the electrochemical processes in conventional electrodes. Herein, we show unambiguous evidence of reversible anionic redox reactions in LiNi 1/3 Co 1/3 Mn 1/3 O 2 . The typical involvement of oxygen through hybridization with transition metals is discussed, as well as the intrinsic oxygen redox process at high potentials, which is 75 % reversible during initial cycling and 63% retained after 10 cycles. Our results clarify the reaction mechanism at high potentials in conventional layered electrodes involving both cationic and anionic reactions and indicate the potential of utilizing reversible oxygen redox reactions in conventional layered oxides for high-capacity lithium-ion batteries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Reversible Anionic Redox Activities in Conventional LiNi 1/3 Co 1/3 Mn 1/3 O 2 Cathodes

Abstract Redox reactions of oxygen have been considered critical in controlling the electrochemical properties of lithium‐excessive layered‐oxide electrodes. However, conventional electrode materials without overlithiation remain the most practical. Typically, cationic redox reactions are believed to dominate the electrochemical processes in conventional electrodes. Herein, we show unambiguous evidence of reversible anionic redox reactions in LiNi 1/3 Co 1/3 Mn 1/3 O 2 . The typical involvement of oxygen through hybridization with transition metals is discussed, as well as the intrinsic oxygen redox process at high potentials, which is 75 % reversible during initial cycling and 63 % retained after 10 cycles. Our results clarify the reaction mechanism at high potentials in conventional layered electrodes involving both cationic and anionic reactions and indicate the potential of utilizing reversible oxygen redox reactions in conventional layered oxides for high‐capacity lithium‐ion batteries.

Lee, Gi‐Hyeok↗
DOE OSTI2021

Reversible dual anionic-redox chemistry in NaCrSSe with fast charging capability

Utilizing the anionic redox reaction opens new approaches for the development of new cathode materials with extra capacities. Although, it suffers from several obstacles such as voltage hysteresis and sluggish kinetics. In this paper, a new layered chalcogenide-based on dual anionic-redox reaction is reported. The newly designed layered NaCrSSe exhibits the capacity of almost all Na + intercalation/deintercalation (137 mAh/g -1 at 50 mA/g), and a unique charge/discharge feature with a small polarization of 0.15 V and high energy efficiency of ~92% in initial cycles. Furthermore, a superior high-rate charge capacity of 115.5mAh/g -1 (83.7% retention) was achieved at 27.8 C (4000 mA/g -1 ). Systematic characterization studies on structure evolution and DFT calculation show the charge compensation of S and Se anions during cycling. Overall, these results will enrich the anion redox chemistry and provide valuable information for developing new anion-redox based cathode materials with high capacity and fast kinetics.

25 ENERGY STORAGE↗
DOE OSTI2022

A Nearly Zero-Strain Li-Rich Rock-Salt Oxide with Multielectron Redox Reactions as a Cathode for Li-Ion Batteries

Li-rich oxide cathodes are drawing increasing attention as next-generation cathode materials for the development of high-energy-density Li-ion batteries due to their strikingly high capacities. However, transition-metal migration, irreversible structural phase transformations, and the irreversible release of oxygen are responsible for rapid capacity and voltage decay. This study reports a Li-rich cation-ordered rock-salt oxide Li x V 0.4 Ti 0.4 O 2 (LVTO, x = 0.97/1.2) with space group Fd$\bar{3}$m that delivers a high capacity of over 250 mAh g -1 and capacity retention up to 89% after 50 cycles. A comprehensive experimental analysis confirms that the capacity can be attributed to the reversible V 3+ /V 5+ multielectron cationic redox reactions and a minor contribution from reversible anionic redox reactions. Importantly, LVTO exhibits nearly zero-strain behavior upon (dis)charge cycling cycles, which is associated with reversible V migration from octahedral to tetrahedral sites. Here our results demonstrate that Li-rich rock-salt oxide LVTO could be a promising cobalt-free cathode material for Li-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2025

Spatial Heterogenous Redox Couples Degradation in Sodium-Ion Battery Cathode Materials and the Mitigation of Voltage Fade by Blocking Oxygen Release

The use of anionic redox has become a new paradigm for improving the energy density of rechargeable batteries, which is essential for improving the market competitiveness of sodium-ion batteries. However, issues such as voltage attenuation and cycling stability degradation persist in layered oxide anion redox cathode materials. Here, in this study, we systematically investigate the classic Na-ion cathode material Na 0.6 Li 0.2 Mn 0.8 O 2 , and the primary causes of voltage decay are identified as the activation of cations and the reduction in anion redox activity. In addition, the activation of cations is closely associated with anion reactions. Through the application of sophisticated multiscale synchrotron absorption spectroscopy and imaging techniques, we have identified a pronounced pattern of spatially dependent degradation in the evolution of redox couples, which is more evident from the material’s surface to its core. With this understanding, we introduced a surface fluorination approach that modulates the local chemical coordination environment. This strategy increases the formation energy of surface oxygen vacancies and locks transition metals oxide state. Consequently, it enables more reversible anionic redox reactions, which block the spatial progression of degradation and mitigates voltage decay.

25 ENERGY STORAGE↗
DOE OSTI2022

Unveiling the High-valence Oxygen Degradation Across the Delithiated Cathode Surface

Charge compensation on anionic redox reaction (ARR) has been promising to realize extra capacity beyond transition metal redox in battery cathodes. The practical development of ARR capacity has been hindered by high-valence oxygen instability, particularly at cathode surfaces. However, the direct probe of surface oxygen behavior has been challenging. Here, the electronic states of surface oxygen are investigated by combining mapping of resonant Auger electronic spectroscopy (mRAS) and ambient pressure X-ray photoelectron spectroscopy (APXPS) on a model LiCoO 2 cathode. The mRAS verified that no high-valence oxygen can sustain at cathode surfaces, while APXPS proves that cathode electrolyte interphase (CEI) layer evolves and oxidizes upon oxygen gas contact. In conclusion, this work provides valuable insights into the high-valence oxygen degradation mode across the interface. Oxygen stabilization from surface architecture is proven a prerequisite to the practical development of ARR active cathodes.

25 ENERGY STORAGE↗
DOE OSTI2025

Uncovering the Critical Role of Ni on Surface Lattice Stability in Anionic Redox Active Li 1.2 Ni 0.2 Mn 0.6 O 2

Anionic redox reaction (ARR) can provide extra capacity beyond transition metal (TM) redox in lithium-rich TM oxide cathodes. Practical ARR application is much hindered by the structure instability, particularly at the surface. Oxygen release has been widely accepted as the ringleader of surficial structure instability. However, the role of TM in surface stability has been much overlooked, not to mention its interplay with oxygen release. Herein, TM dissolution and oxygen release are comparatively investigated in Li 1.2 Ni 0.2 Mn 0.6 O 2 . Ni is verified to detach from the lattice counter-intuitively despite the overwhelming stoichiometry of Mn, facilitating subsequent oxygen release of the ARR process. Intriguingly, surface reorganization occurs following regulated Ni dissolution, enabling the stabilization of the surface and elimination of oxygen release in turn. Accordingly, a novel optimization strategy is proposed by adding a relaxation step at 4.50 V within the first cycle procedure. Battery performance can be effectively improved, with voltage decay suppressed from 3.44 mV/cycle to 1.60 mV/cycle, and cycle stability improved from 66.77% to 90.01% after 100 cycles. This work provides new perspectives for clarifying ARR surface instability and guidance for optimizing ARR performance.

25 ENERGY STORAGE↗
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↗
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 OSTI2024

Correlating concerted cations with oxygen redox in rechargeable batteries

Rechargeable batteries currently power much of our world, but with the increased demand for electric vehicles (EVs) capable of traveling hundreds of miles on a single charge, new paradigms are necessary for overcoming the limits of energy density, particularly in rechargeable batteries. The emergence of reversible anionic redox reactions presents a promising direction toward achieving this goal; however this process has both positive and negative effects on battery performance. While it often leads to higher capacity, anionic redox also causes several unfavorable effects such as voltage fade, voltage hysteresis, sluggish kinetics, and oxygen loss. However, the introduction of cations with topological chemistry tendencies has created an efficient pathway for achieving long-term oxygen redox with improved kinetics. The cations serve as pillars in the crystal structure and meanwhile can interact with oxygen in ways that affect the oxygen redox process through their impact on the electronic structure. This review delves into a detailed examination of the fundamental physical and chemical characteristics of oxygen redox and elucidates the crucial role that cations play in this process at the atomic and electronic scales. Furthermore, here we present a systematic summary of polycationic systems, with an emphasis on their electrochemical performance, in order to provide perspectives on the development of next-generation cathode materials.

25 ENERGY STORAGE↗
DOE OSTI2021

Modulating the Surface Ligand Orientation for Stabilized Anionic Redox in Li‐Rich Oxide Cathodes

Abstract Anionic redox chemistry is emerging as a key concept in the development of high‐energy lithium‐ion batteries, as it enables a nearly doubled charge storage capacity, aiding the development of high‐capacity batteries. However, the anionic reactivity is frequently irreversible from charge to discharge, leading to rapid decay of the capacity and voltage of batteries over long‐term cycling. Although the possibility of controlling the anionic redox reactions by tuning the geometric and electronic structures has recently been proposed, the implementation of this strategy is still a critical challenge. Herein, a strategy is proposed to improve the anionic redox reversibility of a model anionic redox active cathode material, Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 , by tuning the surface ligand geometry via the growth of a lattice‐compatible spinel LiCoO 2 coating layer on the particle surface. Detailed local structure and first principles investigations reveal that the shape and orientation of the octahedral layer in the host lattice are modified. Accordingly, a two‐band oxygen redox behavior is triggered in the ligand‐orientation‐regulated Li‐rich cathode, leading to enhanced reversibility, and thus, remarkably improved capacity and voltage retention over cycling. This study highlights the importance of controllable ligand orientation, carving a new path for the development and design of Li‐rich cathodes in the future.

Liu, Yanchen↗