Loss Of Lattice Oxygen Research Articles

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.

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.

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.

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.

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.

Assessing the Surface Degradation Process of Manganese-Based Li-Ion Battery Cathodes Using Scanning Electrochemical Microscopy

Li-ion batteries (LIBs) are the favored technology driving the market toward sustainable energy sources and electrified transportation. However, cathode materials in LIBs pose a key challenge, limiting both energy storage capacity and cost-effectiveness. Among the different classes of cathode materials, transition metal oxides are most utilized due to their ability to provide high voltage and the reversible Li-ion intercalation during battery operation. Specifically, manganese (Mn)-based oxide cathodes are quite attractive due to their low toxicity and cost1. However, in promising cathodes such as LiMn2O3, Mn3+ ions are Jahn-Teller (J-T) active, making them prone to leaching out in the electrolyte during LIB operation2. The dissolved Mn not only leads to the loss of cathode active material but also gets subsequently deposited on the anodes, leading to gradual capacity fading of the LIB. Therefore, elucidating and addressing this issue continues to be an ongoing endeavor with practical implications.Inductively coupled plasma (ICP) and electron paramagnetic resonance (EPR) spectroscopy are the two most widely used techniques to study the Mn-dissolution phenomenon from LIB cathodes. However, these techniques are typically ex-situ in nature and have low temporal resolution. Furthermore, they offer no spatial information on the heterogeneity of the Mn dissolution from cathode materials, and their limited sensitivity makes it challenging to quantitatively investigate Mn dissolution within a reasonable time frame.This work introduces scanning electrochemical microscopy (SECM) as an in-situ tool to tackle this challenge and enable real-time quantitative investigation of Mn dissolution from LIB cathodes. We utilize LiMn2O3 as a model system to develop the SECM-based method to study Mn dissolution. Mercury (Hg)-based SECM probes allow selective investigation of the Mn dissolving from the cathode with exceptional sensitivity using anodic stripping voltammetry. The close proximity of the SECM probe to the cathode surface (<15 μm) offers high temporal resolution of ~300 ms. Correlating SECM experimental results with COMSOL Multiphysics simulations helps in the quantification of the Mn lost from the cathodes as a function of different cathode operating conditions. In addition, rastering the SECM tip across the cathodes provides the opportunity to study spatial heterogeneity in the Mn dissolution behavior. Furthermore, this work correlates the lattice oxygen loss from LiMn2O3 with Mn dissolution by detecting both oxygen and Mn within the SECM experimental setup, utilizing our previously developed method to investigate lattice oxygen loss from oxide cathodes in LIB3. In summary, this work provides insight into the degradation process of transition-metal oxide-based LIB cathodes involving both lattice oxygen loss and transition metal dissolution.(1) Liu, S.; Wang, B.; Zhang, X.; Zhao, S.; Zhang, Z.; Yu, H. Reviving the Lithium-Manganese-Based Layered Oxide Cathodes for Lithium-Ion Batteries. Matter 2021, 4 (5), 1511–1527. https://doi.org/10.1016/j.matt.2021.02.023.(2) Asl, H. Y.; Manthiram, A. Reining in Dissolved Transition-Metal Ions. Science 2020, 369 (6500), 140–141. https://doi.org/10.1126/science.abc5454.(3) Mishra, A.; Sarbapalli, D.; Hossain, Md. S.; Gossage, Z. T.; Li, Z.; Urban, A.; Rodríguez-López, J. Highly Sensitive Detection and Mapping of Incipient and Steady-State Oxygen Evolution from Operating Li-Ion Battery Cathodes via Scanning Electrochemical Microscopy. J. Electrochem. Soc. 2022, 169 (8), 086501. https://doi.org/10.1149/1945-7111/ac857e.

Integrated hierarchical lanthanum niobium oxide surface coating to stabilize high-voltage performance and suppress Ni2+/Li+ cationic disorder in nickel-rich layered cathodes

High‑nickel ternary materials are the most promising lithium battery cathodes in terms of application and development potential. These materials face significant problems at elevated voltage, including cation mixing, interfacial reactions, microcracks, and lattice oxygen loss, which undermine their cyclic stability and safety. Metal oxide coating is the most direct and effective solution to alleviate this material degradation. Herein, we present an integrated LaNbO4 (LN) surface coating strategy for improving LiNi0.88Mn0.02Co0.10O2's (NMC-88) electrochemical performance and structural stability. The coating materials penetrate the bulk-layered structure and enhance structural integrity. Additionally, it protects the cathode surface against undesirable parasitic side reactions and achieves excellent electrochemical properties, optimal rate performance, and cyclic stability by improving lithium diffusion. The modified cathode maintains a specific capacity of 42 %, while the pristine NMC-88 cathode holds 25.69 % after 150 cycles at 2.8–4.5 V under 2C. The surface modification method reduces the H2-H3 phase and the overgrowth of the solid electrolyte interface, leading to enhanced cyclic performance. In comparison to NMC-88, the improved electrochemical performance and structural integrity of LN-coated NMC-88 are linked to the decrease in microcrack defects during cycling.

Oxyanion Engineering on RuO2 for Efficient Proton Exchange Membrane Water Electrolysis.

In acidic proton exchange membrane water electrolysis (PEMWE), the anode oxygen evolution reaction (OER) catalysts rely heavily on the expensive and scarce iridium-based materials. Ruthenium dioxide (RuO2) with lower price and higher OER activity, has been explored for the similar task, but has been restricted by the poor stability. Herein, we developed an anion modification strategy to improve the OER performance of RuO2 in acidic media. The designed multicomponent catalyst based on sulfate anchored on RuO2/MoO3 displays a low overpotential of 190 mV at 10 mA cm-2 and stably operates for 500 hours with a very low degradation rate of 20 μV h-1 in acidic electrolyte. When assembled in a PEMWE cell, this catalyst as an anode shows an excellent stability at 500 mA cm-2 for 150 h. Experimental and theoretical results revealed that MoO3 could stabilize sulfate anion on RuO2 surface to suppress its leaching during OER. Such MoO3-anchored sulfate not only reduces the formation energy of *OOH intermediate on RuO2, but also impedes both the surface Ru and lattice oxygen loss, thereby achieving the high OER activity and exceptional durability.

Oxyanion Engineering on RuO2 for Efficient Proton Exchange Membrane Water Electrolysis

AbstractIn acidic proton exchange membrane water electrolysis (PEMWE), the anode oxygen evolution reaction (OER) catalysts rely heavily on the expensive and scarce iridium‐based materials. Ruthenium dioxide (RuO2) with lower price and higher OER activity, has been explored for the similar task, but has been restricted by the poor stability. Herein, we developed an anion modification strategy to improve the OER performance of RuO2 in acidic media. The designed multicomponent catalyst based on sulfate anchored on RuO2/MoO3 displays a low overpotential of 190 mV at 10 mA cm−2 and stably operates for 500 hours with a very low degradation rate of 20 μV h−1 in acidic electrolyte. When assembled in a PEMWE cell, this catalyst as an anode shows an excellent stability at 500 mA cm−2 for 150 h. Experimental and theoretical results revealed that MoO3 could stabilize sulfate anion on RuO2 surface to suppress its leaching during OER. Such MoO3‐anchored sulfate not only reduces the formation energy of *OOH intermediate on RuO2, but also impedes both the surface Ru and lattice oxygen loss, thereby achieving the high OER activity and exceptional durability.

Stabilizing the Layer-Structured Oxide Cathode by Modulating the Oxygen Redox Activity for Sodium Ion Batteries.

The layer-structured oxide cathode for sodium-ion batteries has attracted a widespread attention due to the unique redox properties and the anionic redox activity providing additional capacity. Nevertheless, such excessive oxygen redox reactions will lead to irreversible oxygen release, resulting in a rapid deterioration of the cycling stability. Herein, sulfur ion is successfully introduced to the O3-NaNi0.3Mn0.5Cu0.1Ti0.05W0.05O2 material through high-temperature quenching, thereby developing a novel Na2S-modified O3/P2-NaNi0.3Mn0.5Cu0.1Ti0.05W0.05O2 composite with extended cycling life. The S2- is analyzed for the ability to enhance the reversibility of oxidation-reduction reactions under high voltage and suppress the loss of lattice oxygen during cycling. The stable S─O covalent bonds are found to inhibit the oxygen generation and release within the structure. Benefiting from these improvements, the Na₂S-modified O3/P2-NaNi0.3Mn0.5Cu0.1Ti0.05W0.05O2 exhibited a high reversible capacity of 173.1mA h g-1 over a wide voltage range of 1.5-4.3V under test conditions at 0.1 C and 81.5% capacity retention after 120 cycles at 1 C. The Na₂S-modified O3/P2-NaNi0.3Mn0.5Cu0.1Ti0.05W0.05O2 demonstrates the excellent rate capability with the reversible capacities of 173.1,137.0,114.7,96.7, and 80.1mA h g-1 at 0.1, 0.2, 0.5, 1, and 2 C.

Lithium-rich manganese-based layered oxide cathode materials for lithium-ion batteries modified by MoS2 coatings with two-dimensional graphene-like structures

Lithium-rich manganese-based layered oxide cathode materials (LRMCs) have some unique advantages such as high theoretical capacity (≥ 250 mAh g−1) and high energy density. Therefore, they are deemed as a kind of cathode material for lithium-ion batteries with an excellent prospect of application. However, the redox of oxygen anion is able to generate irreversible lattice oxygen loss, leading to irreversible loss of capacity, bringing about a sharp drop of working voltage, and seriously restricting the commercialization of LRMCs. In this paper, MoS2 coating with two-dimensional graphene-like structure was coated on the surface of LRMCs materials for improving the cycling stability and rate performance. The MoS2 coating can provide a two-dimensional diffusion channel for the migration of lithium-ions, which facilitates the fast release of lithium-ions during cycling process. The results show that the first discharge capacity, initial Coulomb efficiency and rate performance of LRMCs are improved. When the current density is 1 C, the first discharge specific capacity of LRMCs@MoS2 reaches 227.69 mAh g−1, and the capacity retention ratio is 84.98 % after 100 cycles. When the current density is 5 C, it can still provide a discharge specific capacity of 137.87 mAh g−1, demonstrating excellent electrochemical performance. This study comes up a simple and practical idea to realize the modification of cathode materials for high performance lithium-ion batteries.

One-step surface-to-bulk modification of single-crystalline Ni-rich Co-poor cathodes for high-rate and long-life Li-ion batteries at high-voltage operations

Single-crystalline Ni-rich Co-poor cathodes operating at high-voltage are attractive owing to their higher energy density for meeting the requirements of next-generation Li-ion batteries, yet they usually suffer from sluggish Li-ion diffusion kinetics and serious Li/Ni disordering. Herein, an in-situ co-precipitation strategy is implemented to achieve the novel In-doped and Li3InO3 coated single-crystalline LiNi0.90Co0.05Mn0.05O2 cathodes with a highly ordered layered structure. The In-doping facilitates grain growth by decreasing the surface energy of crystal faces, reducing the synthesis temperature by about 20 °C, which thus drastically suppresses Li/Ni disordering and lattice oxygen loss. Furthermore, the pillar effect of In-ion doping and the in-situ formation of the ultrafast Li-ion conductive Li3InO3 coating synergistically enhance the Li-ion diffusion kinetics. These merits enable the as-obtained Ni-rich Co-poor cathodes with a high reversible capacity of 229.4 mAh g−1 at 0.1C and 124.6 mAh g−1 at 7C. In a pouch-type full cell, 93.9 % of the initial capacity is still maintained after 500 cycles at 1C within 2.7–4.5 V. This finding opens up a new path for improving the rate performance and cycle life of single-crystalline Ni-rich cathodes for high-voltage Li-ion batteries.

Retarding the capacity fading and voltage decay of Li-rich Mn-based cathode materials via a compatible layer coating for high-performance lithium-ion batteries.

Li-rich Mn-based layered oxides have been considered as the most promising cathode candidate for high energy density lithium ion batteries. However, the practical application of Li-rich Mn-based layered oxides is hindered due to the capacity fading and voltage decay accompanied with structure transition from the layered structure to spinel phase during cycling. Herein, a facile surface structure repair via Ce modification is reported. The structural analysis of the bulk and coating layer was carried out using XRD, XPS, SEM and TEM, which confirmed the successful doping of Ce and formation of a Li2CeO3 coating on the surface. The modified sample LLO-2 delivers a discharge specific capacity of 263.5 mA h g-1 at 0.1C and capacity retention rate with 88.1% at 0.2C after 100 cycles compared to 250.2 mA h g-1 and 75.6% for the pristine sample. The enhanced performance could be because Ce doping enlarges the lattice parameter, which may contribute to accelerating the Li+ diffusion rate. Moreover, the newly formed Li2CeO3 coating with oxygen vacancies could inhibit the loss of lattice oxygen and protect the electrode surface by suppressing the attack from the electrolyte. This work provides an effective approach to design Li-rich Mn-based layered oxides with improved electrochemical performance.

Unravelling the Effect of Sodium Doping on Li2MnO3 nanostructured Cathode Materials

The quest to develop affordable, high-performance electrode materials for lithium-ion batteries in electric vehicles is driving scientific innovation forward. Li2MnO3, as a prospective high-capacity (459 mAh.g-1) cathode, suffers from capacity degradation and voltage decay during the cycling process. Nanostructuring and incorporating sodium ions into lithium sites can mitigate voltage decay by limiting transition metal migration, impeding oxygen loss, and improving lithium diffusion by lowering the activation energy of Li-rich layered host materials. Herein, sodium-incorporated nonospherical structures of the form Li2-xNaxMnO3 (0 ≤ x ≤ 2), generated through the amorphisation and recrystallisation (A+R) technique show remarkable structural stability and enhanced Li-ion mobility owing to the enlarged lithium lattice upon sodium entrance. Specifically, the Li1.95Na0.05NaO3 nanosphere, displays more stable Li+/Mn4+ layers which will greatly contribute to its capacity. The microstructures associated with this configuration show well-ordered layers with high lithium kinetics and lower activation energy compared to pristine Li2MnO3. Characterisation of the x-ray diffraction (XRD) patterns revealed peak broadening along with the shifting of peaks at 2Θ~38 to the right due to the enlarged lithium layers occupied by sodium ions to facilitate lithium diffusion. Moreover, the undesired phase transformation from layered to spinel was observed at a later stage of charge for the sodium-doped systems, suggesting that the presence of sodium stabilizes the structure and minimizes the migration of manganese into lithium layers. These findings may lead to solutions for problems such as structural instability, lattice oxygen loss, and capacity decay in layered lithium oxide materials.

Study on the interface of high specific energy High stability

High nickel terterial oxide, with high specific capacity and low cost advantages, is the preferred positive electrode for high specific energy lithium-ion power batteries at present. However, the high nickel ternary cathode material is easy to have side reactions with the electrolyte in the high delithium state, which can not only lead to the dissolution of transition metal ions and the formation of the surface salt phase, but also cause the lattice oxygen loss and surface interface side reactions, resulting in rapid attenuation of electrode capacity. In this paper, the development history and structural characteristics of high nickel ternary cathode materials are introduced, and the surface interface problems leading to capacity attenuation and structural degradation are comprehensively analyzed. From this perspective, three effective strategies for improving electrochemical performance of high nickel ternary cathode materials are summarized. Finally, by describing the advantages and disadvantages of these layered cathode materials, the challenges faced by these layered cathode materials are discussed, and it is pointed out that in the future, composite modification strategies should be adopted to optimize their structures and improve their properties.

Improving cycling performance of the NaNiO2 cathode in sodium-ion batteries by titanium substitution

O3-type layered oxide cathodes, such as NaNi0.5Mn0.5O2, have garnered significant attention due to their high theoretical specific capacity while using abundant and low-cost sodium as intercalation species. Unlike the lithium analog (LiNiO2), NaNiO2 (NNO) exhibits poor electrochemical performance resulting from structural instability and inferior Coulomb efficiency. To enhance its cyclability for practical application, NNO was modified by titanium substitution to yield the O3-type NaNi0.9Ti0.1O2 (NNTO), which was successfully synthesized for the first time via a solid-state reaction. The mechanism behind its superior performance in comparison to that of similar materials is examined in detail using a variety of characterization techniques. NNTO delivers a specific discharge capacity of ∼190 mAh g−1 and exhibits good reversibility, even in the presence of multiple phase transitions during cycling in a potential window of 2.0‒4.2 V vs. Na+/Na. This behavior can be attributed to the substituent, which helps maintain a larger interslab distance in the Na-deficient phases and to mitigate Jahn–Teller activity by reducing the average oxidation state of nickel. However, volume collapse at high potentials and irreversible lattice oxygen loss are still detrimental to the NNTO. Nevertheless, the performance can be further enhanced through coating and doping strategies. This not only positions NNTO as a promising next-generation cathode material, but also serves as inspiration for future research directions in the field of high-energy-density Na-ion batteries.