Oxygen Loss Research Articles

Explaining deuterium-depleted water as a cancer therapy: a narrative review

Deuterium is a natural heavy isotope of hydrogen, containing a neutron and a proton. This gives it distinct biophysical and biochemical properties, compared with hydrogen. Deuterium alters enzymatic activity in significant ways. Human metabolic processes minimize the amount of deuterium in mitochondrial water, because it causes a dysfunction in mitochondrial ATPase pumps, leading to excessive reactive oxygen species (ROS) and loss of ATP production. Mitochondrial dysfunction is a characteristic feature of cancer and many other diseases. Lactate plays an important role in cancer progression, and a central role holds also for vacuolar ATPases (V-ATPases). In the presence of excess deuterium, cancer cells show a remarkably altered metabolic policy, enabling invasion and proliferation. Cancer cells protect their mitochondria from excessive ROS by minimizing the use of ATPase to synthesize ATP. Instead, they rely on glycolysis to supply ATP and support the massive synthesis of lactate, which is excreted into the microenvironment. They also use V-ATPases in an unusual way at the plasma membrane to pump deuterium-depleted protons out of the cell, enriching cytoplasmic deuterium. These complex processes suggest that cancer cells are able to sense deuterium levels in the medium and commit apoptosis when deuterium levels are low or proliferate when they are high. Tumorigenesis involves a metabolic switch that supports increased cellular deuterium levels, decreasing the deuterium burden overall in the organism. Strong clinical evidence supports deuterium-depleted water (DDW) as an anticancer treatment. More investigations on cancer autophagic behavior are needed to guide DDW clinical use.

Reduction‐Induced Oxygen Loss: the Hidden Surface Reconstruction Mechanism of Layered Oxide Cathodes in Lithium‐Ion Batteries

AbstractThe surface reconstruction from the layered to rocksalt‐type phase represents a primary deterioration pathway of layered‐oxide cathodes in lithium‐ion batteries, involving irreversible oxygen loss and transition metal migration. This degradation mechanism has primarily been attributed to the oxidative instability of highly delithiated cathodes at high voltages (>4.3 V vs Li/Li+). However, the battery degradation also occurs under seemingly stable voltage ranges, the origin of which remains unclear. Herein, a hidden mechanism to induce surface reconstruction and oxygen loss is proposed, termed the “quasi‐conversion reaction”, which is revealed to occur during electrochemical reduction (discharge) processes just below 3.0 V (vs Li/Li+). Combined experiments and first‐principles calculations unveil that the oxygens at the surface can be extracted from the cathode lattice by forming lithium oxides and oxygen vacancies, at significantly higher potentials than conventional conversion reaction, due to the instability of surface oxygens coordinated with fewer cations than in the bulk. The chemical incompatibility between lithium oxides and commercial carbonate‐based electrolytes results in electrolyte decomposition, forming an organic‐rich blocking layer and gaseous byproducts, which further increases the cell impedance. This study emphasizes the necessity of a thorough understanding of surface instability upon reduction to develop long‐lasting batteries.

Suppressing surface segregation by introducing lanthanides to enhance high-temperature oxygen evolution reaction activity and durability

Abstract Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) is a conventional anode material for solid oxide electrolysis cells (SOECs) to catalyze oxygen evolution reactions (OERs). However, the inferior chemical stability of BSCF results in severe surface segregation and performance degradation under high temperatures. A critical challenge lies in alleviating surface segregation and preserving the high OER performance of BSCF anodes. Herein, lanthanides are introduced to substitute the Ba in BSCF, labeled as Ln0.5Sr0.5Co0.8Fe0.2O3−δ (LnSCF, Ln = La, Pr, Nd, Sm), to regulate its stability and performance. The introduction of La and Pr effectively enhances stability, suppresses surface segregation and maintains high OER activity. Continuous lattice oxygen loss and Co ion oxidation of LnSCF are demonstrated upon annealing in oxidizing atmosphere; thus, we propose that surface segregation is a self-regulation mechanism of perovskite lattice to tolerant oxidizing atmosphere. Perovskite oxides maintain structurally stable via decreasing A-site valence state and forming surface segregation. SOECs with La0.5Sr0.5Co0.8Fe0.2O3−δ anodes deliver an optimal current density of 1.69 A cm−2 at 1.6 V and stability for CO2 electrolysis at 800 °C, shedding light on designing advanced catalysts for high-temperature OER.

Stabilizing Lattice Oxygen of Bi2O3 by Interstitial Insertion of Indium for Efficient Formic Acid Electrosynthesis

Bismuth oxide (Bi2O3) emerges as a potent catalyst for converting CO2 to formic acid (HCOOH), leveraging its abundant lattice oxygen and the high activity of its Bi‐O bonds. Yet, its durability is usually impeded by the loss of lattice oxygen causing structure alteration and destabilized active bonds. Herein, we report an innovative approach via the interstitial incorporation of indium (In) into the Bi2O3, significantly enhancing bond stability and preserving lattice oxygen. The optimized In‐Bi2O3‐100 catalyst achieves over 90% Faradaic efficiency for HCOOH production across a wide potential range, in both H‐cells and flow cells, maintaining robust stability after 100 hours of continuous operation. In‐situ surface‐enhanced infrared absorption spectroscopy and theoretical calculations reveal that the interstitial In doping precisely tunes the adsorption of CO2* and OCHO* intermediate, facilitating rapid conversion. Further in‐situ Raman spectroscopy confirms the role of In bolstering the oxidized structure's stability within Bi2O3, critical for sustaining lattice oxygen during electrochemical CO2 reduction.

Stabilizing Lattice Oxygen of Bi2O3 by Interstitial Insertion of Indium for Efficient Formic Acid Electrosynthesis.

Bismuth oxide (Bi2O3) emerges as a potent catalyst for converting CO2 to formic acid (HCOOH), leveraging its abundant lattice oxygen and the high activity of its Bi-O bonds. Yet, its durability is usually impeded by the loss of lattice oxygen causing structure alteration and destabilized active bonds. Herein, we report an innovative approach via the interstitial incorporation of indium (In) into the Bi2O3, significantly enhancing bond stability and preserving lattice oxygen. The optimized In-Bi2O3-100 catalyst achieves over 90% Faradaic efficiency for HCOOH production across a wide potential range, in both H-cells and flow cells, maintaining robust stability after 100 hours of continuous operation. In-situ surface-enhanced infrared absorption spectroscopy and theoretical calculations reveal that the interstitial In doping precisely tunes the adsorption of CO2* and OCHO* intermediate, facilitating rapid conversion. Further in-situ Raman spectroscopy confirms the role of In bolstering the oxidized structure's stability within Bi2O3, critical for sustaining lattice oxygen during electrochemical CO2 reduction.

Bisphenol S induced endothelial dysfunction via mitochondrial pathway in the vascular endothelial cells, and detoxification effect of albumin binding.

As a replacement of bisphenol A, bisphenol S (BPS) is commonly used in the wrappers and food containers of daily life. Epidemiological studies demonstrate a close link between BPS exposure and vascular diseases, where the biological activities of BPS remain scarcely known. Herein, the effects of BPS on endothelial function as well as the underlying mechanism were investigated in human umbilical vein endothelial cells (HUVECs) and mouse arteries. It was found that exposure of BPS dose-dependently induced endothelial dysfunction (i.e., decline of nitric oxide (NO) formation) in HUVECs, accompanied by the increase of reactive oxygen species (ROS) production and loss of mitochondria membrane potential. Mitochondria-specific antioxidant (Mito-Tempol) or superoxide scavenger (tiron) abolished the harmful effects of BPS, while superoxide dismutase (SOD)-specific siRNA exhibited negative influence, suggesting that mitochondrial ROS was responsible for BPS-induced endothelial dysfunction and SOD was a sensitive target of BPS. Consistently, plasma NO formation and endothelium-dependent vasodilation was significantly impaired in mice exposed to dietary BPS. In addition, the binding of bovine serum albumin (BSA, the most abundant protein in blood) to BPS considerably alleviated ROS formation and endothelial dysfunction in HUVECs. BPS primarily interacted with Sudlow site I of albumin to generate BSA-BPS complex through static mechanism, in which the hydrogen bonds and electrostatic forces played important roles. Altogether, dietary exposure to emerging BPS would disrupt vascular homeostasis via the induction of mitochondrial ROS formation and consequent endothelial dysfunction, highlighting the detoxification impact of albumin protein on the hazardous effects of environmental pollutants.

Mechanisms activating trace heavy metals in the rhizosphere microenvironment of Amaranthus hypochondriacus L.

Soil heavy metal activation is closely related to rhizosphere soil pH, O2 and enzyme activity levels. In this study, we used laser ablation inductively coupled plasmamass spectrometry (ICPMS), planar optode (PO), soil in situ enzyme spectrum analysis, and the diffusive gradients in thin films (DGT) method to investigate heavy metal accumulation in Amaranthus hypochondriacus L. growing in polluted soil (Cd, Pb and Zn) and unpolluted soil, as well as dissolved oxygen (DO), pH, soil enzyme activity, and trace heavy metal dynamics in rhizosphere and nonrhizosphere soils. The results revealed that the growth of A. hypochondriacus was significantly inhibited under combined Cd, Pb, and Zn stress, with the most pronounced effects on root and branch biomass. Radial oxygen loss (ROL) and alkalization occurred in the roots of A. hypochondriacus, which were influenced primarily by root growth and environmental conditions. The enzyme activity patterns indicated that acid phosphatase (ACP), alkaline phosphatase (ALP), and β-glucosidase (BG) activities were primarily associated with the root system and that the activities of these enzymes were relatively low in nonrooted soil. Under heavy metal stress, the ACP, ALP and BG activities in the hotspots of soil increased. DO, pH, and soil enzyme activity were significantly correlated with the presence of heavy metals Cd, Pb, and Zn, influencing the mobilization mechanisms of trace metals in the rhizosphere. These findings lay the groundwork for understanding the impact of root-induced alterations in O2, pH, and soil enzyme activity on the mobility of trace heavy metals in soil.

Variation in bioelectricity production in integrated CW-MFC: An insight into coliform inactivation affected by HRT and power density

In the current study, domestic wastewater was treated in three identical vertical up-flow reactors; R1 (constructed wetland), R2 (CW-MFC), and R3 (unplanted CW-MFC) under different HRTs of 36 h (Phase 1), 24 h (Phase 2), and 18h (Phase 3). Periodic reduction of HRT from Phase 1 to Phase 3 resulted in deteriorated organics and fecal coliform removal by the reactors. R2 showed higher pollutant removal and voltage generation in every phase of the study compared to R1 and R3. R2 exerted 93%, 87%, and 57% mean COD removal during Phase 1, Phase 2, and Phase 3; with maximum open circuit voltage generated as 925 mV, 695 mV, and 429 mV respectively. Linear regression analysis showed that operating voltage and power density had significant effects on the variance of effluent fecal coliform concentration. The regression analysis also revealed that 36 h – 24 h HRT was critical where power density influenced the pathogen inactivation considerably. Multiple batch studies revealed the main role of reactor media and plant roots was to support the attached microbial growth for biodegradation of the organics Radial oxygen loss did not affect the anaerobic environment at the anode after 800 days of reactor operation.

Integrated Oxygen-Constraining Strategy for Ni-Rich Layered Oxide Cathodes.

Surface engineering is sought to stabilize nickel-rich layered oxide cathodes in high-energy-density lithium-ion batteries, which suffer from severe surface oxygen loss and rapid structure degradation, especially during deep delithiation at high voltages or high temperatures. Here, we propose a well-designed oxygen-constraining strategy to address the crisis of oxygen evolution. By integrating a La, Fe gradient diffusion layer and a LaFeO3 coating into the Ni-rich layered particles, along with incorporating an antioxidant binder into the electrodes, three progressive lines of defense are constructed: immobilizing the lattice oxygen at the subsurface, blocking the released oxygen at the interface, and capturing the residual singlet oxygen on the external surface. As a result, effective surface passivation, mitigated bulk and surface degradation, suppressed side reactions, and enhanced electrochemical performance are achieved, far beyond conventional single surface modification. The Ni-rich layered oxide cathodes with integrated oxygen-constraining modifications demonstrate impressive cycling stability in both half-cells and full cells, achieving stable long-term cycling even at a high cutoff voltage of 4.7 V and a high temperature of 45 °C. This work provides a multilevel oxygen-constraining strategy, which can be extended to various layered oxide cathodes involving oxygen release challenges, providing an effective path for the development of high-energy-density lithium-ion batteries.

Interface Issues of Layered Transition Metal Oxide Cathodes for Sodium-Ion Batteries: Current Status, Recent Advances, Strategies, and Prospects.

Sodium-ion batteries (SIBs) hold significant promise in energy storage devices due to their low cost and abundant resources. Layered transition metal oxide cathodes (NaxTMO2, TM = Ni, Mn, Fe, etc.), owing to their high theoretical capacities and straightforward synthesis procedures, are emerging as the most promising cathode materials for SIBs. However, the practical application of the NaxTMO2 cathode is hindered by an unstable interface, causing rapid capacity decay. This work reviewed the critical factors affecting the interfacial stability and degradation mechanisms of NaxTMO2, including air sensitivity and the migration and dissolution of TM ions, which are compounded by the loss of lattice oxygen. Furthermore, the mainstream interface modification approaches for improving electrochemical performance are summarized, including element doping, surface engineering, electrolyte optimization, and so on. Finally, the future developmental directions of these layered NaxTMO2 cathodes are concluded. This review is meant to shed light on the design of superior cathodes for high-performance SIBs.

Dual-Doping Strategy for Lowering the Thermal Expansion Coefficient and Promoting the Catalytic Activity in Perovskite Cobaltate Air Electrodes for Solid Oxide Cells.

Lowering the thermal expansion coefficient (TEC) and promoting the catalytic activity of cobalt-based perovskite air electrodes is crucial for efficient solid oxide cells (SOCs) devices. However, the co-achievement of both merits has usually been largely compromised in most scenarios. Herein, a dual-doping strategy to manipulate the properties of perovskite cobaltate electrocatalyst is reported in which a high valence element of Ta5+ is incorporated into B-site to significantly suppress the dynamic reduction of Co4+ species and reduces the TEC value from PrBaCo2O5+δ (PBC, 17.8 × 10⁻6 K-1) to PrBaCo1.96Ta0.04O5+δ (PBCT, 12.5 × 10⁻6 K-1) and suppresses the oxygen loss in SOCs operation condition, revealing the improved structural stability. Meanwhile, the Ca2+ is doped into A-site of Ta-incorporated candidate, further decreasing the covalency of Co─O bonds and facilitating the formation of oxygen vacancies, benefiting the oxygen exchange kinetics and leading to a low polarization resistance of 0.026 Ω cm2 (800 °C) in as-prepared PrBa0.8Ca0.2Co1.96Ta0.04O5+δ (PBCCT) electrode. The cell with PBCTT demonstrates remarkable robustness during a 50 h thermal cycling test (25 cycles). Moreover, it delivers a high current density of 1.44 A cm⁻2 (1.6V, 800 °C), as well as attractive durability over 100 h for pure CO2 electrolysis.

Anisotropic Strain Evolution of Layered LiNi0.5Co0.2Mn0.3O2 Cathode in Formation Cycle.

The formation process plays a key role in developing long life and high energy density materials, during which the phase transition, strain evolution, and structural self-adaption interact rationally with each other to produce a qualified electrode for Li-ion batteries (LIBs). Taking the layered LiNi0.5Co0.2Mn0.3O2 cathode as an example, the substantial structural changes, both in the bulk and at the surface are thoroughly documented during the formation cycle. Upon initial charging, different phases emerge continuously, resulting in lattice mismatches, inhomogeneous strain, and microstructural distortions. The irreversible loss of lattice oxygen, combined with the spontaneous cation mixing and the formation of rock-salt phase at the surface, contributes to the initial capacity loss. As a self-adjustment process, this initial capacity loss facilitates the development of a robust LixNi0.5Co0.2Mn0.3O2 electrode by relieving internal strain and stabilizing the rippled layered structure, thereby ensuring highly reversible electrochemical behavior in subsequent cycles. These findings lay a solid foundation for the design and optimization of layered cathodes for rechargeable batteries.

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 TMO6 octahedral environments, as demonstrated by soft/hard X‐ray absorption spectroscopy. Furthermore, we reveal that a high‐entropy state induced by cationic disordering has capacity to perturb cationic redox boundaries, significantly restraining the formation of detrimental P3' phases. As a consequence, the high‐voltage cycling stability has been greatly enhanced, up to 4.4 V versus Na+/Na, with an impressive 90.1% capacity retention at 1C over 100 cycles and 76.1% capacity retention at 2C over 300 cycles. 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, safe batteries.

Tackling activity-stability paradox of reconstructed NiIrOx electrocatalysts by bridged W-O moiety

One challenge remaining in the development of Ir-based electrocatalyst is the activity-stability paradox during acidic oxygen evolution reaction (OER), especially for the surface reconstructed IrOx catalyst with high efficiency. To address this, a phase selective Ir-based electrocatalyst is constructed by forming bridged W-O moiety in NiIrOx electrocatalyst. Through an electrochemical dealloying process, an nano-porous structure with surface-hydroxylated rutile NiWIrOx electrocatalyst is engineered via Ni as a sacrificial element. Despite low Ir content, NiWIrOx demonstrates a minimal overpotential of 180 mV for the OER at 10 mA·cm−2. It maintains a stable 300 mA·cm−2 current density during an approximately 300 h OER at 1.8 VRHE and shows a stability number of 3.9 × 105 noxygen · nIr−1. The resulting W – O–Ir bridging motif proves pivotal for enhancing the efficacy of OER catalysis by facilitating deprotonation of OER intermediates and promoting a thermodynamically favorable dual-site adsorbent evolution mechanism. Besides, the phase selective insertion of W-O in NiIrOx enabling charge balance through the W-O-Ir bridging motif, effectively counteracting lattice oxygen loss by regulating Ir-O co-valency.

Disulfiram-Loaded Nanoparticles Inhibit Long-Term Proliferation on Preadipocytes.

Disulfiram (DSF) reduces insulin resistance and weight gain in obese mice. However, the effect on adipose tissue is unexplored due to their high instability under physiological conditions, limiting clinical applications. Thus, it is meaningful to develop a DSF carrier for sustained release to adipose tissue. We optimized the synthesis of poly-ε-caprolactone (PCL) nanoparticles (NPs) loaded with DSF and analyzed their effect on adipose tissue cells in vitro. The NPs were synthesized by nanoprecipitation method, varying its solvent, either acetone or acetone/dichloromethane (60:40) (v/v), and ratio PCL:DSF (w/w) 1:2, 1:1, 2:1 and, 1:0; finding the best condition was obtained with acetone/dichloromethane solvent mixture and 2:1 PCL:DSF. Then, NPs toxicity was analyzed on adipose cells (preadipocytes, white-like adipocytes, and macrophages) assessing association and internalization, cell viability, and cell death mechanism. NPs were spherical with a particle size distribution of 203.2 ± 29.33 nm, a ζ-potential of -20.7 ± 4.58 mV, a PDI of 0.296 ± 0.084, and a physical drug loading of 18.6 ± 5.80%. Sustained release was observed from 0.5 h (10.94 ± 2.38%) up to 96h (91.20 ± 6.03%) under physiological conditions. NPs internalize into macrophages, white-like adipocytes and preadipocytes without modifying cell viability on white-like adipocytes and macrophages. Preadipocytes reduce cell viability, inducing mitochondrial damage, increased mitochondrial reactive oxygen species production and loss of mitochondrial membrane potential, leading to effector caspases 3/7 cleaved, resulting in apoptosis. Finally, long-term proliferation inhibition was observed, highlighting the bioequivalent effect of PCL-DSF NPs compared to free DSF. Our data demonstrated the biological interaction of PCL NPs with adipose cells in vitro. The selective cytotoxicity of DSF towards preadipocytes resulted in milder effects when it was delivered nanoencapsulated compared to the free drug. These results suggest promising pharmacological alternatives for DSF long-term delivery on adipose tissue.

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 TMO6 octahedral environments, as demonstrated by soft/hard X-ray absorption spectroscopy. Furthermore, we reveal that a high-entropy state induced by cationic disordering has capacity to perturb cationic redox boundaries, significantly restraining the formation of detrimental P3' phases. As a consequence, the high-voltage cycling stability has been greatly enhanced, up to 4.4 V versus Na+/Na, with an impressive 90.1% capacity retention at 1C over 100 cycles and 76.1% capacity retention at 2C over 300 cycles. 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, safe batteries.

Lattice-Engineering modulated band structure facilitates enhanced stability of high-voltage LiCoO2 at 4.6 V

Lithium cobalt oxide (LCO) cathode materials could exceed 210 mAh g−1 with excellent volumetric energy density, when operated at voltages above 4.5 V. However, the progress in the advancement of high-voltage LCO cathodes is impeded by unstable lattice oxygen loss and rapid structural degradation. Herein, we propose a modification strategy to modulate the band structure and stabilize the crystal structure of LCO through Zr/Ti dual-doping. The modified Zr/Ti-LCO demonstrates stable cycling performance at elevated cut-off voltage of 4.6 V. Uniform co-doping with zirconium and titanium suppresses the severe H1-3/O1 deleterious phase transition of LCO. By fine-tuning TM-O interactions and modulated band structure mitigate oxygen release reactivity at high voltage, achieving a delicate balance between structural integrity and electrochemical stability. Consequently, the modified Zr/Ti-LCO half-cell achieves superb capacity retention of 87.7 % after 300 cycles at 3.0–4.6 V, while the Zr/Ti-LCO||graphite pouch full-cell retains up to 85.8 % capacity after 500 cycles at 3.0–4.5 V. This study offers critical perspectives for advancing the design of high-voltage LCO cathodes.

Lattice strengthening enables reversible anionic redox chemistry in sodium-ion batteries

Triggering anionic redox reaction (ARR) in layered oxide cathodes has emerged as an effective approach to overcoming the energy density limitations of conventional sodium-ion batteries (SIBs) solely based on cationic redox. However, the local structural deterioration and lattice oxygen loss associated with ARR remain challenging and unsolved, resulting in severe capacity and voltage decay. To address these issues, we herein present a lattice-strengthened P2-Na0.66Ca0.03[Li0.24Mn0.76]O2 (NCLMO) cathode. The introduction of Ca into the Na layers enables the compressed TMO2 slabs and reinforced TM–O bonds (TM = Li/Mn). Moreover, the incorporation of Ca into the Na layers effectively mitigates the out-of-plane migration of Li and impedes the in-plane migration of Mn during the anionic redox. The reduction of ion migration reduces the variation of the local environment surrounding O and hinders the formation of TM vacancy clusters, significantly mitigating the loss of lattice oxygen. Consequently, NCLMO delivers an impressive capacity retention of 76.04% at 1 C after 200 cycles. Our findings highlight the significance of maintaining local structural stability and offer novel insights towards achieving highly reversible ARR in layered oxide cathodes for high-energy SIBs.

In–situ construction of LixFeyOz coatings on cobalt–free lithium–rich cathode materials for enhanced structural stability and electrochemical performance

Environmentally benign and cost–effective cobalt–free lithium–rich cathode materials have garnered significant interest. Nevertheless, the irreversible loss of lattice oxygen compromises their structural integrity, leading to capacity fade, voltage decay, and sluggish kinetics, which collectively impede their commercial viability. To address these challenges, this study introduces an in–situ formation of LixFeyOz coatings on the surface of cobalt–free lithium–rich materials by utilizing residual lithium compounds. At elevated temperatures, the residual lithium compounds on the surface of Li1.2Mn0.6Ni0.2O2 (LMNO) react with FeO to generate a LixFeyOz protective layer. This coating not only shields the bulk material from direct exposure to the electrolyte but also effectively consumes residual lithium compounds to suppress interfacial side reactions, thereby enhancing structural stability. The LixFeyOz layer acts as a lithium–ion conductor, facilitating the migration of lithium ions and markedly boosting the material's electrochemical performance. Experimental results indicate that at a current density of 1C, the initial discharge specific capacity of LMNO@Fe is 235.24 mAh g−1 with a capacity retention of 91.33 % after 100 cycles, compared to 211.62 mAh g−1and 77.95 % for LMNO, respectively. Even at a higher current density of 5C, the LMNO@Fe maintains a discharge specific capacity of 148.30 mAh g−1. This research demonstrates that the LixFeyOz coating on cobalt–free lithium–rich cathode materials offers a promising strategy for achieving high–performance lithium–ion batteries.

Experimental & Computational Evidence for Reduced Surface Layer Trapping Li-ions in Ni-rich Li-ion Battery Cathodes

Lithium-ion batteries have proved their dominance in the mobile vehicle market; however, their energy densities need to be increased to facilitate a swifter transition to a greener future.[1] Of the promising materials, nickel-rich layered oxide cathodes emerge as a key contender, where their operation at high voltages allows access to higher capacities, providing an overall increase to the W⋅h/kg.[2] However, at high voltages, degradation in the form of oxygen-loss from the cathode arises for layered oxides.[3] For NMC811, an emerging cathode material, this effect is especially prominent as a mode of suspected degradation when operated under wider voltage windows (2.5–4.4 V). The nature of these species evolved at the surface and their contribution to electrode degradation, are not yet fully understood, and more details need to be uncovered to reliably access higher energy densities in current and next generation cathode materials.Here, we report the use of O K-edge soft X-ray absorption (sXAS) measurements to probe into species variation at the cathode’s surface for single crystal NMC811 full cells cycled at voltages below and above their oxygen loss threshold. The results confirm that operation at high voltage (above oxygen loss) results in the evolution of a layer forming at the surface. Our calculations using Density Functional Theory (DFT) and Ab Initio Molecular Dynamics (AIMD) have allowed us to confirm the nature of this surface being comprised of a reduced nickel oxygen species as an Ni-O ‘rock-salt’ type layer (RSL). We coupled these results with surface measurements using hard X-ray photoelectron spectroscopy (HAXPES) and observed trapped lithium for cells in their charged state, suggesting there is a kinetic barrier hindering their mobility.We then proceeded to understand the relationship of this trapped lithium to the bulk structure using operando XRD measurements. Here, we show that structural fatigue is generated in NMC811 as a consequence of high voltage cycling. This feature of fatigue was evident from the evolution of the 003 reflection from the NMC phase and was seen to develop with prolonged cycling (Fig. 1b & c). This ‘fatigue’ feature in literature has been attributed to trapped lithium in the bulk and has only been observed after long-term cycling.[4] This feature is known to be associated to a reconstructed part of the bulk structure with poor lithium kinetics[4] and here, we observe this feature as early as the first cycle which we attribute to the formation of the RSL. Mitigating the formation of this RSL layer will therefore reduce the kinetic capacity loss, thus this discovery proves promising towards engineering future cathodes with higher utilisable capacities.[1] Drive to electrify. Nature Climate Change, 14, (2024), 299.[2] W. Li, E. M. Erickson, A. Manthiram, High-nickel layered oxide cathodes for lithium-based automotive batteries, Nature Energy, 5, (2020), 26–34.[3] H. Zhang, H. Liu, L. F. J. Piper. M. S. Whittingham, G. Zhou, Oxygen Loss in Layered Oxide Cathodes for Li-Ion Batteries: Mechanisms, Effects, and Mitigation, Chemical Review, 122, (2022), 5641–5681.[4] C. Xu, K. Märker, J. Lee, A. Mahadevegowda, P. J. Reeves, S. J. Day, M. F. Groh, S. P. Emge,C. Ducati, B. L. Mehdi, C. C. Tang, C. P. Grey, Bulk fatigue induced by surface reconstruction in layered Ni-rich cathodes for Li-ion batteries, Nature Materials, 1, (2021), 84–92.[5] A. S. Menon, N. Shah, J.A. Gott, E. Fiamegkou, M. J. W. Ogley, G. J. P. Fajardo, N. Vaenas, I. Ellis, N. Ravichandran, P. Cloetens, D. Karpov, J.M. Warnett, P. Malliband, D. Walker, G. West, M. Loveridge, L. F. J. Piper, Quantifying Electrochemical Degradation in Single-Crystalline LiNi0.8Mn0.1Co0.1O2–Graphite Pouch Cells through Operando X-Ray and Postmortem Investigations, PRX Energy 3, (2024) 013004. Figure 1