Lattice Oxygen Redox Research Articles

Stabilizing lattice oxygen redox in layered sodium transition metal oxide through spin singlet state

Reversible lattice oxygen redox reactions offer the potential to enhance energy density and lower battery cathode costs. However, their widespread adoption faces obstacles like substantial voltage hysteresis and poor stability. The current research addresses these challenges by achieving a non-hysteresis, long-term stable oxygen redox reaction in the P3-type Na2/3Cu1/3Mn2/3O2. Here we show this is accomplished by forming spin singlet states during charge and discharge. Detailed analysis, including in-situ X-ray diffraction, shows highly reversible structural changes during cycling. In addition, local CuO6 Jahn-Teller distortions persist throughout, with dynamic Cu-O bond length variations. In-situ hard X-ray absorption and ex-situ soft X-ray absorption study, along with density function theory calculations, reveal two distinct charge compensation mechanisms at approximately 3.66 V and 3.99 V plateaus. Notably, we observe a Zhang-Rice-like singlet state during 3.99 V charging, offering an alternative charge compensation mechanism to stabilize the active oxygen redox reaction.

Understanding Lattice Oxygen Redox Behavior in Lithium‐Rich Manganese‐Based Layered Oxides for Lithium‐Ion and Lithium‐Metal Batteries from Reaction Mechanisms to Regulation Strategies

AbstractLithium‐rich manganese‐based layered oxides (LMLOs) are considered to be one type of the most promising materials for next‐generation cathodes of lithium batteries due to their distinctive anionic redox processes contributing ultrahigh capacity and energy density. Unfortunately, their practical applications are still plagued by several challenges such as undesirable interfacial reactions and structural evolution, as well as voltage hysteresis/recession, in which irreversible anionic redox behavior bears the brunt as the primacy factor. Undoubtedly, a deep understanding of anionic redox reaction mechanisms and irreversible behavior of oxygen species is crucial in order to provide essential guidance for modification strategies for LMLOs. In this paper, the fundamental understanding of intricate anionic redox reaction mechanisms from thermodynamics models to kinetic anionic redox reaction pathways is comprehensively reviewed, and the existing challenges of LMLOs related with irreversible oxygen reaction behavior are analyzed. Furthermore, numerous representative modification strategies for overcoming these challenges, coupled with their underlying mechanisms for regulating anionic redox reversibility are summarized. In addition, the aspects of multi‐scale structural modifications, integration of interdisciplinary technologies, and application in quasi‐/all‐solid‐state battery systems are given some emphasis in terms of further improvement of LMLOs‐based cathode materials for advanced lithium batteries‐based energy storage systems.

Enhancing Oxygen Evolution Reaction by Simultaneously Triggering Metal and Lattice Oxygen Redox Pair in Iridium Loading on Ni‐Doped Co3O4

AbstractSince the active sites in catalytic systems are either metal sites or lattice oxygen, simultaneously triggering metal and lattice oxygen redox pair with low energy barriers is expected to provide diversified and efficient sites to accelerate oxygen evolution reaction (OER) kinetics, but this is a great challenge. Herein, Ir species (Ir clusters and Ir single atoms) loaded on Ni‐doped Co3O4 is designed (Ir/Ni‐Co3O4), where metallic Ir clusters downsize to spread into high‐density Ir single atoms to load on reconstruction‐derived Ni‐doped CoOOH. In situ spectroscopy, isotope‐labeled, and chemical probe experiments demonstrate that metal site and lattice oxygen are simultaneously activated to participate in the OER. Further theoretical studies demonstrate that the Co site is the most favorable site to promote the OER through an adsorbate evolution mechanism with a low energy barrier of 1.69 eV. The Ni cooperating with Ir atoms synergistically upshifts energy positions of the O p band centers. Thus, the lattice O that bridges Ni and Ir atoms is activated to participate in the OER via coupling with adsorbed O on the Ir site to fulfill O─O bond formation. Benefiting from the conjoint participation of the metal and lattice oxygen redox pair, Ir/Ni‐Co3O4 affords extremely low OER overpotentials of 177 and 263 mV at corresponding 10 and 500 mA cm−2.

Recent Advances in the Comprehension and Regulation of Lattice Oxygen Oxidation Mechanism in Oxygen Evolution Reaction

Water electrolysis, a process for producing green hydrogen from renewable energy, plays a crucial role in the transition toward a sustainable energy landscape and the realization of the hydrogen economy. Oxygen evolution reaction (OER) is a critical step in water electrolysis and is often limited by its slow kinetics. Two main mechanisms, namely the adsorbate evolution mechanism (AEM) and lattice oxygen oxidation mechanism (LOM), are commonly considered in the context of OER. However, designing efficient catalysts based on either the AEM or the LOM remains a topic of debate, and there is no consensus on whether activity and stability are directly related to a certain mechanism. Considering the above, we discuss the characteristics, advantages, and disadvantages of AEM and LOM. Additionally, we provide insights on leveraging the LOM to develop highly active and stable OER catalysts in future. For instance, it is essential to accurately differentiate between reversible and irreversible lattice oxygen redox reactions to elucidate the LOM. Furthermore, we discuss strategies for effectively activating lattice oxygen to achieve controllable steady-state exchange between lattice oxygen and an electrolyte (OH− or H2O). Additionally, we discuss the use of in situ characterization techniques and theoretical calculations as promising avenues for further elucidating the LOM.

Mitigating the Formation of Tetrahedral Zn in Layered Oxides Enables Reversible Lattice Oxygen Redox Triggering by the Na-O-Zn Configuration.

Na-ion layered oxides with Na-O-A' local configurations (A' represents nonredox active cations such as Li+, Na+, Mg2+, Zn2+) are attractive cathode choices for energy-dense Na-ion batteries owing to the accumulation of cationic and anionic redox activities. However, the migration of A' would degrade the stability of the Na-O-A' configuration, bringing about drastic capacity decay and local structural distortions upon cycling. Herein, we uncover the close interplay between irreversible Zn migration and the inactivation of lattice oxygen redox (LOR) for layered oxides based on Na-O-Zn configuration by 23Na solid-state NMR and Zn K-edge EXAFS techniques. We further design a Na2/3Zn0.18Ti0.10Mn0.72O2 cathode in which irreversible Zn migration is effectively prevented, and the LOR reversibility is significantly enhanced. Theoretical insights demonstrate that the migrated Zn2+ is more inclined to occupy the tetrahedral site rather than the prismatic site and can be effectively minimized by incorporation of Ti4+ into the transition-metal layer. Our findings substantiate that the Na-O-Zn configuration can be utilized as an appropriate structure to achieve stable LOR by the cautious manipulating of intralayer cation arrangements.

Lattice Oxygen Redox Reversibility Modulation in Enhancing the Cycling Stability of Li‐Rich Cathode Materials

AbstractThe practical application of lithium‐rich layered oxides is prohibited by the drawbacks such as severe capacity and voltage degradation resulting from unstable oxygen redox environment and the accompanied irreversible oxygen release. Herein, a facile and effective strategy is proposed to regulate the oxygen redox chemistry via foreign Fe doping and its induced intrinsic transition metal (TM) doping as well as the in situ constructed spinel surface layer. The Fe doping, together with the induced intrinsic TM dual doping, can stabilize the lattice oxygen in the bulk due to the formed stronger FeO bond, and restrain the irreversible TM migration and then the undesirable phase transformation. More importantly, thermodynamical energy barrier of oxygen activation is dramatically decreased by the O 2p–Fe 3d charge‐transfer, allowing stable oxygen redox activity. And the pre‐constructed spinel layer can effectively stabilize the surface lattice oxygen and suppress harmful interfacial side‐reactions. Such a simple optimizing method make the modified cathode exhibit a high specific capacity of 298 mAh g−1 at 0.2 C, outstanding cycling stability with a superior capacity and voltage retentions of 92.5% and 90.8%, respectively, after 400 cycles at 1 C. This study provides a new direction for developing advanced Li‐ion batteries.

Computational Understandings of Cation Configuration-Dependent Redox Activity and Oxygen Dimerization in Lithium-Rich Manganese-Based Layered Cathodes

Lithium-rich manganese-based layered oxides have emerged as a fresh paradigm for developing advanced cathode materials with high energy density for next-generation lithium-ion batteries. Understanding lattice oxygen dimerization is quite essential for the optimal design of lithium-rich manganese-based cathode materials. Herein, based on density functional theory (DFT) calculations, a local Ni-honeycomb Li–Ni–Mn cation configuration for the Li1.22Ni0.22Mn0.56O2 cathode was carefully examined, which may coexist with the well-known local Li-honeycomb structure in experimentally synthesized Li1.2Ni0.2Mn0.6O2 samples. The local Li–Ni–Mn cation configurations have significant impacts on oxygen redox activity, transition metal atom migration, and oxygen dimerization in the charging process of LixNi0.22Mn0.56O2. It is found that there is no correlation between high lattice oxygen redox activity and easy oxygen dimerization, such as Li-honeycomb structures simultaneously exhibiting higher oxygen redox activities and higher activation energy barriers for prohibiting oxygen dimerization than Ni-honeycomb structures. The structural regulations of the local Li–Ni–Mn cation configuration by avoiding the local Ni-honeycomb structures to inhibit Mn migration and ease lattice oxygen dimerization and by making full use of the local Li-honeycomb structures would maximize performance of Li-rich Mn-based layered oxides. Such fresh insights provide us a fresh strategy to optimally design the local honeycomb structure for high-performance Li-rich Mn-based cathode materials.

Achieving Long-Enduring High-Voltage Oxygen Redox in P2-Structured Layered Oxide Cathodes by Eliminating Nonlattice Oxygen Redox.

Triggering reversible lattice oxygen redox (LOR) in oxide cathodes is a paradigmatic approach to overcome the capacity ceiling determined by orthodox transition-metal (TM) redox. However, the LOR reactions in P2-structured Na-layered oxides are commonly accompanied by irreversible nonlattice oxygen redox (non-LOR) and large local structural rearrangements, bringing about capacity/voltage fading and constantly evolving charge/discharge voltage curves. Herein, a novel Na0.615 Mg0.154 Ti0.154 Mn0.615 ◻0.077 O2 (◻=TM vacancies) cathode with both NaOMg and NaO◻ local configurations is deliberately designed. Intriguingly, the activating of oxygen redox at middle-voltage region (2.5-4.1V) via NaO◻ configuration helps in maintaining the high-voltage plateau from LOR (≈4.38V) and stable charge/discharge voltage curves even after 100 cycles. Hard X-ray absorption spectroscopy (hXAS), solid-state NMR, and electron paramagnetic resonance studies demonstrate that both the involvement of non-LOR at high-voltage and the structural distortions originating from Jahn-Teller distorted Mn3+ O6 at low-voltage are effectively restrained in Na0.615 Mg0.154 Ti0.154 Mn0.615 ◻0.077 O2 . Resultantly, the P2 phase is well retained in a wide electrochemical window of 1.5-4.5V (vs Na+ /Na), resulting in an extraordinary capacity retention of 95.2% after 100 cycles. This work defines an effective approach to upgrade the lifespan of Na-ion battery with reversible high-voltage capacity provided by LOR.

X-ray Absorption Spectroscopy Illustrates the Participation of Oxygen in the Electrochemical Cycling of Li4Mn2O5

A combination of oxygen redox and Mn-based oxides would be the best option for high-energy-density Li-ion batteries crucial for a sustainable society. The disordered rock-salt Li4Mn2O5 was recently reported to display a very large capacity of 460 mAh/g with moderate reversibility. Previous studies proposed the involvement of lattice oxygen redox in such intriguing electrochemical performance, whereas no direct evidence was presented. To clarify the charge compensation mechanism, we systematically investigated the evolution of the electronic structure of both Mn and O upon cycling via Mn/O K-edge X-ray absorption spectroscopy (XAS). Mn K-edge XAS unequivocally demonstrates the participation of Mn redox upon the initial stages of charging, yet changes are arrested at the high potentials, while O continues to evolve according to O K-edge XAS. Upon discharging, both Mn and O are simultaneously reduced, but to states different from pristine. The results highlight the significance of a disordered structure in maintaining the reversible redox chemistry of both transition metals and oxygen to design cathode materials with high energy density.

Unusual double ligand holes as catalytic active sites in LiNiO2

Designing efficient catalyst for the oxygen evolution reaction (OER) is of importance for energy conversion devices. The anionic redox allows formation of O-O bonds and offers higher OER activity than the conventional metal sites. Here, we successfully prepare LiNiO2 with a dominant 3d8L configuration (L is a hole at O 2p) under high oxygen pressure, and achieve a double ligand holes 3d8L2 under OER since one electron removal occurs at O 2p orbitals for NiIII oxides. LiNiO2 exhibits super-efficient OER activity among LiMO2, RMO3 (M = transition metal, R = rare earth) and other unary 3d catalysts. Multiple in situ/operando spectroscopies reveal NiIII→NiIV transition together with Li-removal during OER. Our theory indicates that NiIV (3d8L2) leads to direct O-O coupling between lattice oxygen and *O intermediates accelerating the OER activity. These findings highlight a new way to design the lattice oxygen redox with enough ligand holes created in OER process.

Lattice Oxygen Activation for Enhanced Electrochemical Oxygen Evolution

Lattice oxygen redox of solid-state material hosts is an emerging observation in electrochemistry. Toward the anodic oxygen evolution reaction (OER) in water electrolysis with sluggish kinetics, the activation of lattice oxygen alters the reaction mechanism profoundly, either facilitating the nucleophilic attack of O–O coupling in the conventional adsorbate evolution mechanism (AEM) or directly triggering the participation of lattice oxygen into gaseous O2 generation via the lattice oxygen-mediated mechanism (LOM). In-depth understanding at the molecular level further provides the research community with fundamental guidelines for advanced OER catalyst design. Herein, we present the physicochemical principles of correlation between the band alignment and the preferential OER mechanism. The recent progress about the key roles of lattice oxygen activation in OER activity improvement is then comprehensively discussed. Finally, we propose the remaining challenges and future perspectives of lattice oxygen activation for the potential advancements in electrocatalysis.

Boosting oxygen evolution reaction performance via metal defect-induced lattice oxygen redox reactions on spinel oxides

LOM catalysts were created by controlling the production of metal defects, resulting in highly efficient OER. The induction of metal defects caused electron delocalization and redistributed electron density between the metal and ligand.

Ozone catalytic oxidation of low-concentration formaldehyde over ternary Mn-Ce-Ni oxide catalysts modified with FeOx.

Manganese oxide-based catalysts have attracted extensive attention due to their relatively low cost and remarkable performance for removing VOCs. In this research, we used the Pechini method to synthesize manganese-cerium-nickel ternary oxide catalysts (MCN) and evaluated the effectiveness of catalytic destruction of formaldehyde (HCHO) and ozone at room temperature. FeOx prepared by the impregnation method was applied to modify the catalyst. After FeOx treatment, the catalyst represented the best performance on both HCHO destruction and ozone decomposition under dry conditions and exhibited excellent water vapor resistance.The as-prepared catalystswere next characterized via H2-temperature programmed reduction (H2-TPR), temperature programmed desorption of O2 (O2-TPD), and X-ray photoelectron spectroscopy (XPS), and the results demonstrated that addition of FeOx increased Mn3+ and Ce3+ concentrations, oxygen vacancies and surface lattice oxygen species, facilitated adsorption, and redox properties. Based on the results of in situ diffuse reflectance infrared Fourier transform spectrometry (DRIFTS), possible mechanisms of ozone catalytic oxidation of HCHO were proposed. Overall, the ternary mixed-oxide catalyst developed in this study holds great promise for HCHO and ozone decomposition in the indoor environment.

Synergistic effect of multiple vacancies to induce lattice oxygen redox in NiFe-layered double hydroxide OER catalysts

The role of multiple vacancies containing cation and anion defects in NiFe layered double hydroxide (LDH) is still worth pursuing in electrocatalytic oxygen evolution reaction (OER). Herein, a strategy integrating the oxygen and iron vacancies is proposed to fabricate NiFe LDH with highly efficient OER performance. More Fe vacancies have been introduced with increasing Fe content in NiFe-LDH structure; operando electrochemical characterizations and density functional theory (DFT) calculations reveal that the synergic effect between the iron and the oxygen vacancies promotes the generation of reconstructed active layers, optimizing the adsorption free energy of oxygen-containing intermediates. More importantly, active NiOOH intermediate species induced by oxygen vacancies are associated with OH- intercalation pseudocapacitance, activating lattice oxygen during water oxidation. The as-prepared Ni0.3Fe0.7-LDH@NF showed ultralow overpotentials of 184 and 287 mV to achieve 10 and 400 mA·cm-2, respectively. Our work provides a new paradigm for designing high-efficiency OER electrocatalysts.

(Digital Presentation) Elucidation of Active Oxygen Sites upon Delithiation of Li3IrO4

Transformational increases in the storage capacity of battery cathodes could be achieved by tapping into the redox activity at oxide ligands in addition to conventional transition metal couples. Yet the key signatures that govern such lattice oxygen redox (LOR) have not been ascertained. Li3IrO4 has the largest reversible LOR, rendering it a unique model system. Here, X-ray spectroscopy and computational simulations reveal that LOR in Li3IrO4 is selectively compensated via O sites with 3 lone pairs, which are activated by Li/Ir disorder. The 2-electron LOR can be reversed to regenerate the initial state without unlocking competing bulk reactions observed in many other compounds. We uncover an intricate interplay between stoichiometry, O coordination and non-bonding states in LOR and pinpoint spectroscopic signatures. This interplay is indispensable to design materials with 3d metals that fulfill the promise of LOR to overcome the bottlenecks of current cathodes for future implementation in practical batteries.

Correlating Mg Displacement with Topologically Regulated Lattice Oxygen Redox in Na-Ion Layered Oxide Cathodes

Correlating Mg Displacement with Topologically Regulated Lattice Oxygen Redox in Na-Ion Layered Oxide Cathodes

π-type orbital hybridization and reactive oxygen quenching induced by Se-doping for Li-rich Mn-based oxide cathode

Li-rich Mn-based oxide cathodes for next generation high-energy-density batteries are unprecedentedly enticing; however, its implementation has been largely plagued by capacity fading and potential decline, mainly associated with the irreversible lattice oxygen redox and structure rearrangements. Hereby, electrochemically stable Li-rich Mn-based oxide cathode is successfully designed by manipulating molecular polarity within host structure through the introduction of Se. Notably, the restructured electronic distribution around lattice oxygen is aroused from weak electronegativity of Se in the bulk. It is beneficial for enhancing the π -type orbital hybridization between O 2p and Mn 3d(t 2g ) due to the lowered energy level of O 2p states, resulting in the mitigation of lattice oxygen loss, which is strongly validated by ex-situ soft/hard X-ray absorption spectroscopy coupled with density functional theory calculations. Concomitantly, reactive oxygen species is deactivated with anti-aging effects in the primary/second particle sub-surface, considerably suppressing the S N 2 attack related to electrolyte decomposition and subsequent transition metals dissolution to render a well-knit cathode electrolyte interface, intensively verified by time-off light secondary-ion mass spectrometry. Greatly, the as-designed Se-LRM delivers excellent long cycling stability after 400 loops with only a 0.029% capacity fading and 1.37 mV potential decline per cycle. Given this, this elaborate work might inaugurate a potential avenue for rationally tuning the structure/interface evolution towards advanced electrodes in lithium-ion batteries.

Quantifying the Anomalous Local and Nanostructure Evolutions Induced by Lattice Oxygen Redox in Lithium-Rich Cathodes.

Due to their accessible lattice oxygen redox (l-OR) at high voltages, Li-rich layered transition metal (TM) oxides have shown promising potential as candidate cathodes for high-energy-density Li-ion batteries. However, this l-OR process is also associated with unusual electrochemical issues such as voltage hysteresis and long-term voltage decay. The structure response mechanism to the l-OR behavior also remains unclear, hindering rational structure optimizations that would enable practical Li-rich cathodes. Here, this study reveals a strong coupling between l-OR and structure dynamic evolutions, as well as their effects on the electrochemical properties. Using the technique of neutron total scattering with pair distribution function analysis and small-angle neutron scattering, this study quantifies the local TM migration and formation of nanopores that accompany the l-OR. These experiments demonstrate the causal relationships among l-OR, the local/nanostructure evolutions, and the unusual electrochemistry. The TM migration triggered by the l-OR can change local oxygen coordination environments, which results in voltage hysteresis. Coupled with formed oxygen vacancies, it will accelerate the formation of nanopores, inducing a phase transition, and leading to irreversible capacity and long-cycling voltage fade.

Research progress of key materials and engineering exploration for Na-ion batteries

<p indent="0mm">Under the background of “Carbon Peaking and Carbon Neutrality”, Na-ion batteries (NIBs) have attracted much attention due to their advantages such as low cost, high safety, and excellent performance. Low-cost NIBs are beneficial supplements to Li-ion batteries and will show their special advantages in the field of energy storage. Nowadays, NIBs are at a critical point from laboratory exploration to industrialization promotion. Since 2011, the NIBs research group of the Institute of Physics, Chinese Academy of Sciences has been committed to the research and development of low-cost, high-safety and high-performance NIBs technologies. It has obtained more than 40 patents of core materials, and some patents have been authorized from the United States, Japan and the European Union. It is the first time in the world to propose Cu-based oxide cathode materials and low-cost anthracite-based anode materials with independent intellectual properties. In 2017, relying on the core patented technology, the first high-tech enterprise focusing on the development and manufacture of NIBs—HaiNa Battery Technology Co. Ltd. was established. Then, the world’s first example application of <sc>100 kW h</sc> and <sc>1 MW h</sc> NIBs energy storage systems was put forward. This paper firstly focuses on the series of progress in the layered oxide cathode materials made by the research group for NIBs, mainly including: (1) Cost-effective Cu-Fe-Mn layered cathode materials, (2) high-capacity lattice oxygen redox layered oxide cathodes, and (3) stable phase transition layered cathode materials (high entropy and high sodium content P2-type cathodes), and poly-anion compound phosphate cathode materials. In terms of anodes, a series of hard carbon anodes using different biomass materials with excellent sodium storage performance were synthesized, as well as the high-performance soft carbon anode materials based on anthracite and pitch. A long-cycle stable titanium-based oxide anode material was designed. In terms of electrolytes, high-salt-concentration aqueous electrolytes and low-salt-concentration inaqueous electrolytes were designed. In addition, NASICON (Na super ionic conductor) type solid electrolytes and polymer solid electrolytes were modified on purpose. For the mechanism investigation of electrode materials, this paper explores in detail the phase formation mechanism of layered cathode materials, the ordered/disordered arrangement of layered oxides, the sodium storage mechanism of titanium-based oxides, the design methods of new tunnel-type materials, the sodium storage mechanism of amorphous carbon materials, and the sodium storage mechanism of organic anode materials. Finally, in terms of the industrialization exploration of NIBs, the process in the industrialization exploration and example application of NIBs for our group was introduced. The future development directions of NIBs were put forward in order to promote the sustainable development and accelerate the commercial application of NIBs.

Correlation of Oxygen Anion Redox Activity to In‐Plane Honeycomb Cation Ordering in NaxNiyMn1−yO2 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 NaxNiyMn1−yO2 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 NaxNiyMn1−yO2 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.