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Iron/manganese‐based layered transition metal oxides have risen to prominence as prospective cathodes for sodium‐ion batteries (SIBs) owing to their abundant resources and high theoretical specific capacities, yet they still suffer from rapid capacity fading. Herein, a dual‐strategy is developed to boost the Na‐storage performance of the Fe/Mn‐based layered oxide cathode by copper (Cu) doping and nanoengineering. The P2‐Na0.76Cu0.22Fe0.30Mn0.48O2 cathode material synthesized by electrospinning exhibits the pearl necklace‐like hierarchical nanostructures assembled by nanograins with sizes of 50–150 nm. The synergistic effects of Cu doping and nanotechnology enable high Na+ coefficients and low ionic migration energy barrier, as well as highly reversible structure evolution and Cu/Fe/Mn valence variation upon repeated sodium insertion/extraction; thus, the P2‐Na0.76Cu0.22Fe0.30Mn0.48O2 nano‐necklaces yield fabulous rate capability (125.4 mA h g−1 at 0.1 C with 56.5 mA h g−1 at 20 C) and excellent cyclic stability (≈79% capacity retention after 300 cycles). Additionally, a promising energy density of 177.4 Wh kg−1 is demonstrated in a prototype soft‐package Na‐ion full battery constructed by the tailored nano‐necklaces cathode and hard carbon anode. This work symbolizes a step forward in the development of Fe/Mn‐based layered oxides as high‐performance cathodes for SIBs. Pearl necklace‐like hierarchical nanostructures of a P2‐Na0.76Cu0.22Fe0.30Mn0.48O2 cathode are synthesized by electrospinning and evaluated in sodium‐ion batteries. The synergistic effects of Cu doping and nanoengineering enable high Na+ coefficients and low ionic migration energy barrier, as well as highly reversible structure evolution and Cu/Fe/Mn valence variation upon repeated sodium insertion/extraction, rendering fabulous rate capability and excellent cyclic stability.

The pursuit of high energy density while achieving long cycle life remains a challenge in developing transition metal (TM) oxide cathode materials for sodium‐ion batteries (SIBs). Here, we present a concept of precisely manipulating structural evolution via local coordination chemistry regulation to design high‐performance composite cathode materials. The controllable structural evolution process is realized by tuning magnesium content in Na 0.6 Mn 1− x Mg x O 2 , which is elucidated by a combination of experimental analysis and theoretical calculations. The substitution of Mg into Mn sites not only induces a unique structural evolution from layered–tunnel structure to layered structure but also mitigates the Jahn–Teller distortion of Mn 3+ . Meanwhile, benefiting from the strong ionic interaction between Mg 2+ and O 2− , local environments around O 2− coordinated with electrochemically inactive Mg 2+ are anchored in the TM layer, providing a pinning effect to stabilize crystal structure and smooth electrochemical profile. The layered–tunnel Na 0.6 Mn 0.95 Mg 0.05 O 2 cathode material delivers 188.9 mAh g −1 of specific capacity, equivalent to 508.0 Wh kg −1 of energy density at 0.5C, and exhibits 71.3% of capacity retention after 1000 cycles at 5C as well as excellent compatibility with hard carbon anode. This work may provide new insights of manipulating structural evolution in composite cathode materials via local coordination chemistry regulation and inspire more novel design of high‐performance SIB cathode materials. image

Layered transition‐metal (TM) oxides are ideal hosts for Li+ charge carriers largely due to the occurrence of oxygen charge compensation that stabilizes the layered structure at high voltage. Hence, enabling charge compensation in sodium layered oxides is a fascinating task for extending the cycle life of sodium‐ion batteries. Herein a Ti/Mg co‐doping strategy for a model P2‐Na2/3Ni1/3Mn2/3O2 cathode material is put forward to activate charge compensation through highly hybridized O2pTM3d covalent bonds. In this way, the interlayer OO electrostatic repulsion is weakened upon deeply charging, which strongly affects the systematic total energy that transforms the striking P2–O2 interlayer contraction into a moderate solid‐solution‐type evolution. Accordingly, the cycling stability of the codoped cathode material is improved superiorly over the pristine sample. This study starts a perspective way of optimizing the sodium layered cathodes by rational structural design coupling electrochemical reactions, which can be extended to widespread battery researches. Here a Ti/Mg codoping strategy for a model P2‐Na2/3Ni1/3Mn2/3O2 (NNM) cathode material is proposed to activate oxygen charge compensation at high voltage. In this way, the interlayer OO electrostatic repulsion is released, which modifies the P2–O2 transition into a moderate solid‐solution type evolution, and therefore remarkably enhances the cycling performance of the P2‐type NNM layered cathode.

Li‐rich Mn‐based layered oxides (LLO) hold great promise as cathode materials for lithium‐ion batteries (LIBs) due to their unique oxygen redox (OR) chemistry, which enables additional capacity. However, the LLOs face challenges related to the instability of their OR process due to the weak transition metal (TM)‐oxygen bond, leading to oxygen loss and irreversible phase transition that results in severe capacity and voltage decay. Herein, a synergistic electronic regulation strategy of surface and interior structures to enhance oxygen stability is proposed. In the interior of the materials, the local electrons around TM and O atoms may be delocalized by surrounding Mo atoms, facilitating the formation of stronger TM─O bonds at high voltages. Besides, on the surface, the highly reactive O atoms with lone pairs of electrons are passivated by additional TM atoms, which provides a more stable TM─O framework. Hence, this strategy stabilizes the oxygen and hinders TM migration, which enhances the reversibility in structural evolution, leading to increased capacity and voltage retention. This work presents an efficient approach to enhance the performance of LLOs through surface‐to‐interior electronic structure modulation, while also contributing to a deeper understanding of their redox reaction. Here a synergistic strategy in Li‐richMn‐based cathodes is proposed to enhance oxygen stability. In this way, lonepair electrons of surface oxygen are passivated, while the local electronsaround transition metal (TM) and O atoms in the bulk are delocalized by Moatoms, forming stronger TM‐O bonds under high voltages. Thus, the reversibilityof the structure is significantly improved.

Layered lithium‐rich manganese‐based oxide (LRMO) has the limitation of inevitable evolution of lattice oxygen release and layered structure transformation. Herein, a multilayer reconstruction strategy is applied to LRMO via facile pyrolysis of potassium Prussian blue. The multilayer interface is visually observed using an atomic‐resolution scanning transmission electron microscope and a high‐resolution transmission electron microscope. Combined with the electrochemical characterization, the redox of lattice oxygen is suppressed during the initial charging. In situ X‐ray diffraction and the high‐resolution transmission electron microscope demonstrate that the suppressed evolution of lattice oxygen eliminates the variation in the unit cell parameters during initial (de)lithiation, which further prevents lattice distortion during long cycling. As a result, the initial Coulombic efficiency of the modified LRMO is up to 87.31%, and the rate capacity and long‐term cycle stability also improved considerably. In this work, a facile surface reconstruction strategy is used to suppress vigorous anionic redox, which is expected to stimulate material design in high‐performance lithium ion batteries.

High‐voltage nickel (Ni)‐rich layered oxide‐based lithium metal batteries (LMBs) exhibit a great potential in advanced batteries due to the ultra‐high energy density. However, it is still necessary to deal with the challenges in poor cyclic and thermal stability before realizing practical application where cycling life is considered. Among many improved strategies, mechanical and chemical stability for the electrode electrolyte interface plays a key role in addressing these challenges. Therefore, extensive effort has been made to address the challenges of electrode‐electrolyte interface. In this progress, the failure mechanism of Ni‐rich cathode, lithium metal anode and electrolytes are reviewed, and the latest breakthrough in stabilizing electrode‐electrolyte interface is also summarized. Finally, the challenges and future research directions of Ni‐rich LMBs are put forward. Lithium metal batteries show the great potential in advanced batteries due to their ultra‐high energy density. This article discusses the failure mechanisms of Ni‐rich cathodes, lithium metal anodes, and electrolytes, and overviews the latest breakthroughs in stabilizing the electrode electrolyte interface from the aspect of electrolytes.

Nickel‐rich layered oxides (LiNixCoyMnzO2, NCM) are among the most promising cathode materials for high‐energy lithium‐ion batteries, offering high specific capacity and output voltage at a relatively low cost. However, industrial‐scale co‐precipitation presents significant challenges, particularly in maintaining particle sphericity, ensuring a stable concentration gradient, and preserving production yield when transitioning from lab‐scale compositions. This study addresses a critical issue in the large‐scale synthesis of nickel‐rich NCM (x = 0.8381): nickel leaching, which compromises particle uniformity and battery performance. To mitigate this, we optimize the reaction process and develop an artificial intelligence‐driven defect prediction system that enhances precursor stability. Our domain adaptation based machine learning model, which accounts for equipment wear and environmental variations, achieves a defect detection accuracy of 97.8% based on machine data and process conditions. By implementing this approach, we successfully scale up NCM precursor production to over 2 tons, achieving 83% capacity retention after 500 cycles at a 1C rate. In addition, the proposed approach demonstrates the formation of a concentration gradient in the composition and a high sphericity of 0.951 (±0.0796). This work provides new insights into the stable mass production of NCM precursors, ensuring both high yield and performance reliability. This work pioneers an AI‐driven defect prediction system and optimized scheduling to enhance the stability of nickel‐rich layered oxide precursors, enabling large‐scale production. With an 83% capacity retention after 500 cycles and exceptional sphericity, it sets a new benchmark for the stable, high‐yield synthesis of advanced lithium‐ion battery cathodes.

Sodium‐ion batteries (SIBs) are considered as a low‐cost complementary or alternative system to prestigious lithium‐ion batteries (LIBs) because of their similar working principle to LIBs, cost‐effectiveness, and sustainable availability of sodium resources, especially in large‐scale energy storage systems (EESs). Among various cathode candidates for SIBs, Na‐based layered transition metal oxides have received extensive attention for their relatively large specific capacity, high operating potential, facile synthesis, and environmental benignity. However, there are a series of fatal issues in terms of poor air stability, unstable cathode/electrolyte interphase, and irreversible phase transition that lead to unsatisfactory battery performance from the perspective of preparation to application, outside to inside of layered oxide cathodes, which severely limit their practical application. This work is meant to review these critical problems associated with layered oxide cathodes to understand their fundamental roots and degradation mechanisms, and to provide a comprehensive summary of mainstream modification strategies including chemical substitution, surface modification, structure modulation, and so forth, concentrating on how to improve air stability, reduce interfacial side reaction, and suppress phase transition for realizing high structural reversibility, fast Na+ kinetics, and superior comprehensive electrochemical performance. The advantages and disadvantages of different strategies are discussed, and insights into future challenges and opportunities for layered oxide cathodes are also presented. Recent progress in layered oxide cathodes for sodium‐ion batteries (SIBs) from air stability, interface chemistry, and phase transition are comprehensively summarized. The intrinsic degradation mechanisms behind electrochemical performance and mainstream modification strategies are systematically sorted out and analyzed. The remaining challenges, promising optimization strategies as well as endeavor directions to break current limitations are also presented for the future design of high‐performance layered oxide cathodes for SIBs.

Because of the low price and abundant reserves of sodium compared with lithium, the research of sodium-ion batteries (SIBs) in the field of large-scale energy storage has returned to the research spotlight. Layered oxides distinguish themselves from the mains cathode materials of SIBs owing to their advantages such as high specific capacity, simple synthesis route, and environmental benignity. However, the commercial development of the layered oxides is limited by sluggish kinetics, complex phase transition and poor air stability. Based on the research ideas from macro- to micro-scale, this review systematically summarizes the current optimization strategies of sodium-ion layered oxide cathodes (SLOC) from different dimensions: microstructure design, local chemistry regulation and structural unit construction. In the dimension of microstructure design, the various structures such as the microspheres, nanoplates, nanowires and exposed active facets are prepared to improve the slow kinetics and electrochemical performance. Besides, from the view of local chemistry regulation by chemical element substitution, the intrinsic electron/ion properties of SLOC have been enhanced to strengthen the structural stability. Furthermore, the optimization idea of endeavors to regulate the physical and chemical properties of cathode materials essentially is put forward from the dimension of structural unit construction. The opinions and strategies proposed in this review will provide some inspirations for the design of new SLOC in the future.

P2-type layered oxide, Na 2/3 Ni 1/3 Mn 2/3 O 2 , has drawn particular interest as a promising cathode material for sodium-ion batteries (SIBs) due to its fast sodium-ion transport channels with low migration potential. However, some catastrophic flaws, such as air instability, complicated multiphase evolution, and irreversible anionic redox, limit its electrochemical performance and hinder its application. Here, an air-stable single-crystal P2-type Na 2/3 Ni 1/3 Mn 1/3 Ti 1/3 O 2 is proposed based on the multifunctional structural modulation of Ti substitution that could alleviate the issues for practical SIBs. As a result, the cathode with high energy density shows excellent air stability and highly reversible phase transitions (P2-OP4), and delivers faster kinetics and stable anion redox chemistry. Meanwhile, a thorough investigation of the relationship between structure, function, and properties is demonstrated, emphasizing formation processes, electrochemical behavior, structural evolution, and air stability. Overall, this study provides the direction of multifunctional structural modulation for the development of high-performance sodium-based layered cathode materials for practical applications.