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Solid‐state lithium–air batteries (SSLABs) have become the focus of next‐generation advanced batteries due to their safety and high energy densities. Current research on SSLABs is mainly centered on solid‐state electrolytes (SSEs). Although SSEs exhibit excellent properties, such as good stability, high safety, and great mechanical strength, they also display several distinct weaknesses of low ionic conductivities, poor stabilities in air, and high interfacial impedances, which will require sustained attentions for further investigations. This review first overviews the development history of SSEs achieved in terms of Li–air batteries. Subsequently, the fundamental properties, preparation methods, merits and drawbacks of different SSEs, along with their use in SSLABs, and the optimization strategy, especially for the inorganic solid electrolytes, polymer electrolytes, and hybrid electrolytes are comprehensively summarized. Finally, the research progresses made with SSEs are outlined, and critical insights and approaches for the remaining challenges of electrolytes and commercial application of SSLABs are proposed, which include advanced characterization, combining experiments and artificial intelligence such as theoretical calculations, and constructing selective permeability membranes. It is expected that this timely review will provide researchers with an integrated, systematic, and in‐depth understanding of SSEs and guidelines for future research, thus further promoting the commercial application of SSLABs. [ABSTRACT FROM AUTHOR]

Cobalt substitution for manganese sites in Na0.44MnO2 initiates a dynamic structural evolution process, yielding a composite cathode material comprising intergrown P2 and P3 phases. The novel P2/P3 composite cathode exhibits a reversible phase transition process during Na+ extraction/insertion, showcasing its attractive battery performance in sodium-ion batteries. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (NIBs) have emerged as a promising alternative to commercial lithium‐ion batteries (LIBs) due to the similar properties of the Li and Na elements as well as the abundance and accessibility of Na resources. Most of the current research has been focused on the half‐cell system (using Na metal as the counter electrode) to evaluate the performance of the cathode/anode/electrolyte. The relationship between the performance achieved in half cells and that obtained in full cells, however, has been neglected in much of this research. Additionally, the trade‐off in the relationship between electrochemical performance and cost needs to be given more consideration. Therefore, systematic and comprehensive insights into the research status and key issues for the full‐cell system need to be gained to advance its commercialization. Consequently, this review evaluates the recent progress based on various cathodes and highlights the most significant challenges for full cells. Several strategies have also been proposed to enhance the electrochemical performance of NIBs, including designing electrode materials, optimizing electrolytes, sodium compensation, and so forth. Finally, perspectives and outlooks are provided to guide future research on sodium‐ion full cells. [ABSTRACT FROM AUTHOR]

Hydrogen‐bonded organic frameworks (HOFs) are considered as potential choice for future energy storage systems due to their adjustable chemistry, environment friendliness, and cost‐effectiveness. In this study, structurally stabilized and aldehyde‐tuned hydrogen‐bonded organic frameworks (HOFs‐8) are designed and prepared to contain arrayed electronegative sites for sodium‐ion storage. Benefitting from the flexible hydrogen bond and unique structural symmetry, HOFs‐8 can achieve efficient utilization of the active sites and fast transport of sodium ions and electrons. The HOFs‐8 electrode exhibits an impressive lifespan of 5000 cycles at 3.66 A g−1 (20 C). In situ Fourier Transform infrared spectroscopy (in situ FT‐IR) and ex situ X‐ray Photoelectron Spectroscopy (ex situ XPS) analyses are performed to illustrate the mechanism of sodium‐ion storage involving aldehyde‐tuned C═O. Additionally, flexible hydrogen bonds in HOFs materials with unique structural symmetries are investigated to elucidate the mechanism of hydrogen bonding for improving their electrochemical properties. Density functional theory (DFT) simulations verified that HOFs‐8 has excellent Na+ diffusion kinetics, enabling it to demonstrate outstanding rate capability. This work offers insight into the design of new electrodes and improved HOFs, which are expected to have tremendous potential in energy storage systems. [ABSTRACT FROM AUTHOR]

Zn deposition with a surface‐preferred (002) crystal plane has attracted extensive attention due to its inhibited dendrite growth and side reactions. However, the nucleation and growth of the Zn(002) crystal plane are closely related to the interfacial properties. Herein, oriented growth of Zn(002) crystal plane is realized on Ag‐modified surface that is directly visualized by in situ atomic force microscopy. A solid solution HCP‐Zn (~1.10 at. % solubility of Ag, 30 °C) is formed on the Ag coated Zn foil (Zn@Ag) and possesses the same crystal structure as Zn to reduce its nucleation barrier caused by their lattice mismatch. It merits oriented Zn deposition and corrosion‐resistant surface, and presents long cycling stability in symmetric cells and full cells coupled with V2O5 cathode. This work provides insights into interfacial regulation of Zn anodes for high‐performance aqueous zinc metal batteries. [ABSTRACT FROM AUTHOR]

Zn deposition with a surface‐preferred (002) crystal plane has attracted extensive attention due to its inhibited dendrite growth and side reactions. However, the nucleation and growth of the Zn(002) crystal plane are closely related to the interfacial properties. Herein, oriented growth of Zn(002) crystal plane is realized on Ag‐modified surface that is directly visualized by in situ atomic force microscopy. A solid solution HCP‐Zn (~1.10 at. % solubility of Ag, 30 °C) is formed on the Ag coated Zn foil (Zn@Ag) and possesses the same crystal structure as Zn to reduce its nucleation barrier caused by their lattice mismatch. It merits oriented Zn deposition and corrosion‐resistant surface, and presents long cycling stability in symmetric cells and full cells coupled with V2O5 cathode. This work provides insights into interfacial regulation of Zn anodes for high‐performance aqueous zinc metal batteries. [ABSTRACT FROM AUTHOR]

Sodium-ion batteries (SIBs) are experiencing a large-scale renaissance to supplement or replace expensive lithium-ion batteries (LIBs) and low energy density lead-acid batteries in electrical energy storage systems and other applications. In this case, layered oxide materials have become one of the most popular cathode candidates for SIBs because of their low cost and comparatively facile synthesis method. However, the intrinsic shortcomings of layered oxide cathodes, which severely limit their commercialization process, urgently need to be addressed. In this review, inherent challenges associated with layered oxide cathodes for SIBs, such as their irreversible multiphase transition, poor air stability, and low energy density, are systematically summarized and discussed, together with strategies to overcome these dilemmas through bulk phase modulation, surface/interface modification, functional structure manipulation, and cationic and anionic redox optimization. Emphasis is placed on investigating variations in the chemical composition and structural configuration of layered oxide cathodes and how they affect the electrochemical behavior of the cathodes to illustrate how these issues can be addressed. The summary of failure mechanisms and corresponding modification strategies of layered oxide cathodes presented herein provides a valuable reference for scientific and practical issues related to the development of SIBs. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Alloying‐type antimony (Sb) with high theoretical capacity is a promising anode candidate for both lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs). Given the larger radius of Na+ (1.02 Å) than Li+ (0.76 Å), it was generally believed that the Sb anode would experience even worse capacity degradation in SIBs due to more substantial volumetric variations during cycling when compared to LIBs. However, the Sb anode in SIBs unexpectedly exhibited both better electrochemical and structural stability than in LIBs, and the mechanistic reasons that underlie this performance discrepancy remain undiscovered. Here, using substantial in situ transmission electron microscopy, X‐ray diffraction, and Raman techniques complemented by theoretical simulations, we explicitly reveal that compared to the lithiation/delithiation process, sodiation/desodiation process of Sb anode displays a previously unexplored two‐stage alloying/dealloying mechanism with polycrystalline and amorphous phases as the intermediates featuring improved resilience to mechanical damage, contributing to superior cycling stability in SIBs. Additionally, the better mechanical properties and weaker atomic interaction of Na−Sb alloys than Li−Sb alloys favor enabling mitigated mechanical stress, accounting for enhanced structural stability as unveiled by theoretical simulations. Our finding delineates the mechanistic origins of enhanced cycling stability of Sb anode in SIBs with potential implications for other large‐volume‐change electrode materials. [ABSTRACT FROM AUTHOR]

Alloying‐type antimony (Sb) with high theoretical capacity is a promising anode candidate for both lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs). Given the larger radius of Na+ (1.02 Å) than Li+ (0.76 Å), it was generally believed that the Sb anode would experience even worse capacity degradation in SIBs due to more substantial volumetric variations during cycling when compared to LIBs. However, the Sb anode in SIBs unexpectedly exhibited both better electrochemical and structural stability than in LIBs, and the mechanistic reasons that underlie this performance discrepancy remain undiscovered. Here, using substantial in situ transmission electron microscopy, X‐ray diffraction, and Raman techniques complemented by theoretical simulations, we explicitly reveal that compared to the lithiation/delithiation process, sodiation/desodiation process of Sb anode displays a previously unexplored two‐stage alloying/dealloying mechanism with polycrystalline and amorphous phases as the intermediates featuring improved resilience to mechanical damage, contributing to superior cycling stability in SIBs. Additionally, the better mechanical properties and weaker atomic interaction of Na−Sb alloys than Li−Sb alloys favor enabling mitigated mechanical stress, accounting for enhanced structural stability as unveiled by theoretical simulations. Our finding delineates the mechanistic origins of enhanced cycling stability of Sb anode in SIBs with potential implications for other large‐volume‐change electrode materials. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) with wide operating temperature are regarded as promising candidates for large‐scale energy storage systems. However, SIBs operating under elevated temperature aggravate the electrolyte decomposition with unstable cathode‐electrolyte interphase (CEI), causing a rapid capacity degradation. Herein, anion receptor tris(pentafluorophenyl)borane (TPFPB) is selected as electrolyte additive to construct robust NaF‐rich CEI. The strong interactions between anion and TPFPB via the electron‐deficient boron atoms weaken ClO4− solvation and promote the coordination capability between solvents and Na+ cations, demonstrating greatly improved oxidative stability. Na3V2(PO4)3 cathode in TPFPB‐containing electrolyte delivers long‐term stability with a capacity retention of 86.9% after 100 cycles at a high cut‐off voltage of 4.2 V (vs. Na+/Na) and a high temperature of 60 °C. Besides, TPFPB also works well with enhanced performance over a temperature range from −30 to 60 °C. This study proposes a prospective method by manipulating the solvation chemistry for constructing high‐temperature rechargeable SIBs. [ABSTRACT FROM AUTHOR]

Given the merits of affordable cost, superior low‐temperature performance, and advanced safe properties, sodium‐ion batteries (SIBs) have exhibited great development potential in large scale energy storage applications. Among various emerging carbonaceous anode materials applied for SIBs, hard carbon (HC) has recently gained significant attention regarding their relatively low cost, wide availability, and optimal overall performance. However, the insufficient initial Coulombic efficiency (ICE) of HC is the main bottlenecks, which is inevitably hindering their further commercial applications. Herein, an in‐depth holistic exposition about the reasons causing the unsatisfied ICE and the recent advances on effective improvement strategies are comprehensively summarized in this review, which have been divided into two aspects including the intrinsic property (degree of graphitization, pore structure, defect, et al.) and the extrinsic factor (electrolyte, electrode materials, et al.). In addition, future prospects and perspectives on HC to enable practical application in SIBs are also briefly outlined. [ABSTRACT FROM AUTHOR]

Sodium (Na) metal anodes are promising candidates for various batteries with high energy density and high‐power density, however, the dendrite growth of Na metal is impeding their practical applications. The binary alloy Na–K is in the liquid state at room temperature with a wide composition range, which renders it inherently free from solid dendrite growth. Whereas the application of Na–K alloy is plagued by the lack of a wettable matrix to immobilize the liquid metal. Herein, a facile method is reported to introduce oxygen‐rich functional groups into carbon fiber cloth (O‐CFC), which is initially Na–K phobic yet turns into superwetting after the treatment. The superwetting behavior of the O‐CFC can be attributed to the favorable enthalpy changes as a result of the introduction of O‐rich functional groups. The superwetting property of the O‐CFC exhibits good universality, which can be extended to melting Na and K metals. By adopting the superwetting O‐CFC as a host for liquid Na–K alloy, the liquid metal can be well retained in the matrix and deliver a stable cycling for >1600 h. The concept of enthalpy‐driven wettability regulation can be enlightening for the host material design of other liquid metals and alloys. [ABSTRACT FROM AUTHOR]

Sodium dual‐ion batteries (Na‐DIBs) have attracted increasing attention due to their high operative voltages and low‐cost raw materials. However, the practical applications of Na‐DIBs are still hindered by the issues, such as low capacity and poor Coulombic efficiency, which is highly correlated with the compatibility between electrode and electrolyte but rarely investigated. Herein, fluoroethylene carbonate (FEC) is introduced into the electrolyte to regulate cation/anion solvation structure and the stability of cathode/anode‐electrolyte interphase of Na‐DIBs. The FEC modulates the environment of PF6− solvation sheath and facilitates the interaction of PF6− on graphite. In addition, the NaF‐rich interphase caused by the preferential decomposition of FEC effectively inhibits side reactions and pulverization of anodes with the electrolyte. Consequently, Sb||graphite full cells in FEC‐containing electrolyte achieve an improved capacity, cycling stability and Coulombic efficiency. This work elucidates the underlying mechanism of bifunctional FEC and provides an alternative strategy of building high‐performance dual ion batteries. [ABSTRACT FROM AUTHOR]

Sodium dual‐ion batteries (Na‐DIBs) have attracted increasing attention due to their high operative voltages and low‐cost raw materials. However, the practical applications of Na‐DIBs are still hindered by the issues, such as low capacity and poor Coulombic efficiency, which is highly correlated with the compatibility between electrode and electrolyte but rarely investigated. Herein, fluoroethylene carbonate (FEC) is introduced into the electrolyte to regulate cation/anion solvation structure and the stability of cathode/anode‐electrolyte interphase of Na‐DIBs. The FEC modulates the environment of PF6− solvation sheath and facilitates the interaction of PF6− on graphite. In addition, the NaF‐rich interphase caused by the preferential decomposition of FEC effectively inhibits side reactions and pulverization of anodes with the electrolyte. Consequently, Sb||graphite full cells in FEC‐containing electrolyte achieve an improved capacity, cycling stability and Coulombic efficiency. This work elucidates the underlying mechanism of bifunctional FEC and provides an alternative strategy of building high‐performance dual ion batteries. [ABSTRACT FROM AUTHOR]

Rechargeable batteries currently hold the largest share of the electrochemical energy storage market, and they play a major role in the sustainable energy transition and industrial decarbonization to respond to global climate change. Due to the increased popularity of consumer electronics and electric vehicles, lithium-ion batteries have quickly become the most successful rechargeable batteries in the past three decades, yet growing demands in diversified application scenarios call for new types of rechargeable batteries. Tremendous efforts are made to developing the next-generation post-Li-ion rechargeable batteries, which include, but are not limited to solid-state batteries, lithium–sulfur batteries, sodium-/potassium-ion batteries, organic batteries, magnesium-/zinc-ion batteries, aqueous batteries and flow batteries. Despite the great achievements, challenges persist in precise understandings about the electrochemical reaction and charge transfer process, and optimal design of key materials and interfaces in a battery. This roadmap tends to provide an overview about the current research progress, key challenges and future prospects of various types of rechargeable batteries. New computational methods for materials development, and characterization techniques will also be discussed as they play an important role in battery research. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

In alkaline seawater electrolysis, the oxygen evolution reaction (OER) is greatly suppressed by the occurrence of electrode corrosion due to the formation of hypochlorite. Herein, a catalyst consisting of MoC nanowires modified with NiFe alloy nanoparticles (NiFe/MoC) on nickel foam (NF) is prepared. The optimized catalyst can deliver a large current density of 500 mA cm−2 at a very low overpotential of 366 mV in alkaline seawater, respectively, outperforming commercial IrO2. Remarkably, an electrolyzer assembled with NiFe/MoC/NF as the anode and NiMoN/NF as the cathode only requires 1.77 V to drive a current density of 500 mA cm−2 for alkaline seawater electrolysis, as well as excellent stability. Theory calculation indicates that the initial activity of NiFe/MoC is attributed to increased electrical conductivity and decreased energy barrier for OER due to the introduction of Fe. We find that the change of the catalyst in the composition occurred after the stability test; however, the reconstructed catalyst has an energy barrier close to that of the pristine one, which is responsible for its excellent long‐term stability. Our findings provide an efficient way to construct high‐performance OER catalysts for alkaline seawater splitting. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) present great appeal in various energy storage systems, especifically for stationary grid storage, on account of the abundance of sources and low cost. Unfortunately, the commercialization of SIBs is mainly limited by available electrode materials, especially for the cathodes. Prussian blue analogs (PBAs), emerge as a promising alternative for their structural feasibility in the application of SIBs. Decreasing the defects (vacancies and coordinated water) is an effective strategy to achieve superior electrochemical performance during the synthetic processes. Herein, we summarize crystal structures, synthetic methods, electrochemical mechanisms, and the influences of synthesis conditions of PBAs in detail. This comprehensive overview on the current research progresses of PBAs will give guides and directions to solve the existing problems for their application in SIBs. [ABSTRACT FROM AUTHOR]

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 Na0.6Mn1−xMgxO2, 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 Mn3+. Meanwhile, benefiting from the strong ionic interaction between Mg2+ and O2−, local environments around O2− coordinated with electrochemically inactive Mg2+ are anchored in the TM layer, providing a pinning effect to stabilize crystal structure and smooth electrochemical profile. The layered–tunnel Na0.6Mn0.95Mg0.05O2 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. [ABSTRACT FROM AUTHOR]

High‐voltage lithium‐ion batteries (LIBs) have attracted great attention due to their promising high energy density. However, severe capacity degradation is witnessed, which originated from the incompatible and unstable electrolyte‐electrode interphase at high voltage. Herein, a robust additive‐induced sulfur‐rich interphase is constructed by introducing an additive with ultrahigh S‐content (34.04 %, methylene methyl disulfonate, MMDS) in 4.6 V LiNi0.5Co0.2Mn0.3O2 (NCM523)||graphite pouch cell. The MMDS does not directly participate the inner Li+ sheath, but the strong interactions between MMDS and PF6− anions promote the preferential decomposition of MMDS and broaden the oxidation stability, facilitating the formation of an ultrathin but robust sulfur‐rich interfacial layer. The electrolyte consumption, gas production, phase transformation and dissolution of transition metal ions were effectively inhibited. As expected, the 4.6 V NCM523||graphite pouch cell delivers a high capacity retention of 87.99 % even after 800 cycles. This work shares new insight into the sulfur‐rich additive‐induced electrolyte‐electrode interphase for stable high‐voltage LIBs. [ABSTRACT FROM AUTHOR]

High‐voltage lithium‐ion batteries (LIBs) have attracted great attention due to their promising high energy density. However, severe capacity degradation is witnessed, which originated from the incompatible and unstable electrolyte‐electrode interphase at high voltage. Herein, a robust additive‐induced sulfur‐rich interphase is constructed by introducing an additive with ultrahigh S‐content (34.04 %, methylene methyl disulfonate, MMDS) in 4.6 V LiNi0.5Co0.2Mn0.3O2 (NCM523)||graphite pouch cell. The MMDS does not directly participate the inner Li+ sheath, but the strong interactions between MMDS and PF6− anions promote the preferential decomposition of MMDS and broaden the oxidation stability, facilitating the formation of an ultrathin but robust sulfur‐rich interfacial layer. The electrolyte consumption, gas production, phase transformation and dissolution of transition metal ions were effectively inhibited. As expected, the 4.6 V NCM523||graphite pouch cell delivers a high capacity retention of 87.99 % even after 800 cycles. This work shares new insight into the sulfur‐rich additive‐induced electrolyte‐electrode interphase for stable high‐voltage LIBs. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metals is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

As a class of promising cathodes in the field of large-scale power storage systems especially for alkali-metal-ion batteries (MIBs), Prussian blue (PB) and its analogues (PBAs) have received wide research attention due to their open framework, high theoretical specific capacity, and simple synthesis method. For large-scale applications, cathode materials with low-cost and long cycle life are preferred. However, only a few of the review papers have concentrated on the detailed analysis of low-cost PBAs, including Fe-based and Mn-based PBAs, which also show excellent electrochemical performance. This review aims to first provide an all-sided understanding of low-cost PBAs in terms of their application and recent progress in MIBs. Then, the major challenges such as inferior electrochemical properties of low-cost PBAs are discussed. Meanwhile, we provide feasible strategies to prepare PBA electrodes with advanced electrochemical performance. Finally, we present some personal perspectives and guidance for future research, aiming to narrow the gap between laboratory investigation and practical application. [ABSTRACT FROM AUTHOR]

Prussian blue analogues (PBAs) have been regarded as promising cathode materials for alkali‐ion batteries owing to their high theoretical energy density and low cost. However, the high water and vacancy content of PBAs lower their energy density and bring safety issues, impeding their large‐scale application. Herein, a facile "potassium‐ions assisted" strategy is proposed to synthesize highly crystallized PBAs. By manipulating the dominant crystal plane and suppressing vacancies, the as‐prepared PBAs exhibit increased redox potential resulting in high energy density up to ≈450 Wh kg−1, which is at the same level of the well‐known LiFePO4 cathodes for lithium‐ion batteries. Remarkably, unconventional highly‐reversible phase evolution and redox‐active pairs were identified by multiple in situ techniques for the first time. The preferred guest‐ion storage sites and migration mechanism were systematically analysed through theoretical calculations. We believe these results could inspire the design of safe with high energy density. [ABSTRACT FROM AUTHOR]

Prussian blue analogues (PBAs) have been regarded as promising cathode materials for alkali‐ion batteries owing to their high theoretical energy density and low cost. However, the high water and vacancy content of PBAs lower their energy density and bring safety issues, impeding their large‐scale application. Herein, a facile "potassium‐ions assisted" strategy is proposed to synthesize highly crystallized PBAs. By manipulating the dominant crystal plane and suppressing vacancies, the as‐prepared PBAs exhibit increased redox potential resulting in high energy density up to ≈450 Wh kg−1, which is at the same level of the well‐known LiFePO4 cathodes for lithium‐ion batteries. Remarkably, unconventional highly‐reversible phase evolution and redox‐active pairs were identified by multiple in situ techniques for the first time. The preferred guest‐ion storage sites and migration mechanism were systematically analysed through theoretical calculations. We believe these results could inspire the design of safe with high energy density. [ABSTRACT FROM AUTHOR]

The development of large‐scale energy storage systems (ESSs) aimed at application in renewable electricity sources and in smart grids is expected to address energy shortage and environmental issues. Sodium‐ion batteries (SIBs) exhibit remarkable potential for large‐scale ESSs because of the high richness and accessibility of sodium reserves. Using low‐cost and abundant elements in cathodes with long cycling stability is preferable for lowering expenses on cathodes. Many investigated cathodes for SIBs are dogged by structural and morphology changes, unstable interphases between the cathode and the electrolyte, and air sensitivity, causing unsatisfactory cycling performance. Therefore, understanding the mechanism of capacity degeneration in depth and developing precise solutions are critical for designing low‐cost cathodes that are highly stable under cycling. Herein, recent progress in long‐cycle‐life and low‐cost cathodes for SIBs is focused on, and a comprehensive discussion of the key points in SIBs toward large‐scale applications is provided. The roots of the unstable cycling performance of low‐cost cathodes are discussed. Also, effective strategies are summarized from the recent progress on long‐cycle‐life and low‐cost cathodes. This review is expected to encourage deeper investigation of long‐lifespan cathodes for SIBs, particularly for potential large‐scale industrialization. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Hard carbon (HC) anodes have shown extraordinary promise for sodium‐ion batteries, but are limited to their poor initial coulombic efficiency (ICE) and low practical specific capacity due to the large amount of defects. These defects with oxygen containing groups cause irreversible sites for Na+ ions. Highly graphited carbon decreases defects, while potentially blocking diffusion paths of Na+ ions. Therefore, molecular‐level control of graphitization of hard carbon with open accessible channels for Na+ ions is key to achieve high‐performance hard carbon. Moreover, it is challenging to design a conventional method to obtain HCs with both high ICE and capacity. Herein, a universal strategy is developed as manganese ions‐assisted catalytic carbonization to precisely tune graphitization degree, eliminate defects, and maintain effective Na+ ions paths. The as‐prepared hard carbon has a high ICE of 92.05% and excellent cycling performance. Simultaneously, a sodium storage mechanism of "adsorption‐intercalation‐pore filling‐sodium cluster formation" is proposed, and a clear description given of the boundaries of the pore structure and the specific dynamic process of pore filling. [ABSTRACT FROM AUTHOR]

Carbon nanospheres (CNSs) have attracted great interest in energy conversion and storage technologies due to their excellent chemical and thermal stability, high electrical conductivity and controllable size structure characteristics. In order to further improve the energy storage properties, many efforts have been made to design suitable nanocarbon spherical materials to improve electrochemical performance. In this overview, we summarize the recent research progress on CNSs, mainly focusing on the synthesis methods and their application as high-performance electrode materials in rechargeable batteries. As for the synthesis methods, hard template methods, soft template methods, the extension of the Stöber method, hydrothermal carbonization, aerosol-assisted synthesis are described in detail. In addition, the use of CNSs as electrodes in energy storage devices (mainly concentrated on lithium-ion batteries (LIBs)), sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) are also discussed in detail in this article. Finally, some perspectives on the future research and development of CNSs are provided. [ABSTRACT FROM AUTHOR]

Layered transition metal oxide (NaxTMO2), being one of the most promising cathode candidates for sodium‐ion batteries (SIBs), have attracted intensive interest because of their nontoxicity, high theoretical capacities, and easy manufacturability. However, their physical and electrochemical properties of water sensitivity, sluggish Na+ transport kinetics, and irreversible multiple‐phase translations hinder the practical application. Here, a concept of surface lattice‐matched engineering is proposed based on in situ spinel interfacial reconstruction to design a spinel coating P2/P3 heterostructure cathode material with enhanced air stability, rate, and cycle performance. The novel structure and its formation process are verified by transmission electron microscopy and in situ high‐temperature X‐ray diffraction. The electrode exhibits an excellent rate performance with the highly reversible phase transformation demonstrated by in situ charging/discharging X‐ray diffraction. Additionally, even after a rigorous water sensitivity test, the electrode materials still retain almost the same superior electrochemical performance as the fresh sample. The results show that the surface spinel phase can play a vital role in preventing the ingress of water molecules, improving transport kinetics, and enhancing structural integrity for NaxTMO2 cathodes. The concept of surface lattice‐matched engineering based on in situ spinel interfacial reconstruction will be helpful for designing new ultra‐stable cathode materials for high‐performance SIBs. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (SIBs) show tremendous potential for large‐scale energy storage systems due to the high abundance of sodium resources and potentially low cost. Among the discovered anode materials for SIBs, metal selenides with large theoretical capacities are considered as a promising candidate. Nevertheless, metal selenide‐based anodes are trapped by poor ionic/electronic conductivity, low initial Coulombic efficiency, and drastic volume changes during the (de)sodiation process. Herein, the differences in sodium‐storage mechanisms of different metal selenides are first analyzed. Subsequently, the specific challenges and corresponding modification strategies (such as nanostructure design, carbon modification, potential window regulation, electrolyte optimization, and constructing heterostructures) for metal selenides as SIB anodes are discussed in detail, and recent advances are also presented. Finally, the potential research directions of metal selenides in SIBs are comprehensively reviewed. It is believed that this review can provide constructive comments on the optimization and large‐scale application of high‐performance metal selenide‐based anode for SIBs. [ABSTRACT FROM AUTHOR]

Aqueous zinc-ion batteries (AZIBs) based on high-safety zinc metal anodes have advantages of low cost and high theoretical capacity and are considered as a promising large-scale energy storage system. Their practical application, however, is hampered by slow transport kinetics, low energy density, and poor cycling performance. In this work, we design and successfully synthesize ultrastable lattice water-rich VO2·xH2O materials by considering the fact that abundant crystallized water can act as "water lubrication", and a charge shielding medium to weaken the electrostatic effect. As a result, VO2·xH2O as a cathode for AZIBs can provide a specific capacity of 376 mA h g−1 after 200 cycles at 1 A g−1 and no apparent capacity decay after 8000 cycles at 15 A g−1. The excellent zinc storage performance can be ascribed to the efficient kinetics and abundant reaction sites of the VO2·xH2O electrode. A series of in situ and ex situ characterizations indicate that it is the H+/Zn2+ co-intercalation mechanism to store zinc in the VO2·xH2O electrode. In short, the abundant crystallized water vanadium-based materials may be excellent candidates for advanced cathode materials of AZIBs. [ABSTRACT FROM AUTHOR]

Room‐temperature sodium–sulfur (RT‐Na/S) batteries are emerging as promising candidates for stationary energy‐storage systems, due to their high energy density, resource abundance, and environmental benignity. A better understanding of RT‐Na/S batteries in the view of the whole battery components is of essential importance for fundamental research and practical applications. In particular, the components other than sulfur cathodes in preventing the migration of polysulfides and accelerating the reaction kinetics have been greatly overlooked. Such a biased research trend is also adverse to the broader applications for RT‐Na/S batteries, which have long been ignored in previous reviews. Herein, approaches to the historical progress toward practical RT‐Na/S batteries through a "teamwork" perspective are comprehensively summarized, and balanced research trends are encouraged to enable practical RT‐Na/S batteries. In the meantime, the persisting issues, promising solutions, and practical applications of advanced sulfur host design, Na metal anode protection, electrolyte optimization, separator modification, and binder engineering are clearly emphasized. Finally, the device‐scale evaluation in practical parameters and advanced characterization tools are thoroughly provided. This review aims to provide the "teamwork" perspective on the whole‐cell design and fundamental guidelines that can shed light on research directions for practical RT‐Na/S batteries. [ABSTRACT FROM AUTHOR]

Sodium‐ion oxide cathodes with triphase heterostructures have attracted intensive attention, since the sodium‐storage performance can be enhanced by utilizing the synergistic effect of different phases. However, the composite structures generally suffer from multiple irreversible phase transitions and high lattice strain because of interlayer‐gliding during the charge/discharge process. Here, the concept of strain engineering via manipulating the local chemistry of heterostructured oxide cathode is proposed to regulate the relevant physical and chemical properties, resulting in highly reversible structural evolution (P2/P3/spinel → P2/P3″/spinel) and low intrinsic stress in the potential window of 1.5–4.0 V. Also, the simple structural evolution at a relatively high cut‐off potential of 4.3 V can be detected by in situ X‐ray diffraction and other electrochemical characterization techniques during Na+ extraction/insertion. Meanwhile, the electrode exhibits a high reversible capacity (169.4 mAh g−1 at 0.2 C) and excellent rate performance from 1.5 to 4.3 V. Overall, this study reveals the mechanisms of regulating local chemistry to realize strain engineering of the cathode materials and paves the way for the further improvement of high‐performance sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

Sodium metal batteries are recognized as promising candidates for next‐generation energy storage devices, as a result of their high energy density, low redox potential, and cheap material price. Na metal anodes, however, generally exhibit notorious problems, including progressively thickened interfaces with active Na loss and Na metal dendrite growth with safety hazards. Herein, a lightweight aerogel consisting of MgF2 nanocrystals grown on a reduced graphene oxide (RGO) aerogel matrix (MgF2@RGO) is rationally designed as a multifunctional host material for Na metal anodes. The MgF2 nanocrystals can be electrochemically converted in situ into Mg and NaF nanograins during the first Na plating process, in which the Mg works as sodiophilic nucleation seeds for Na plating and NaF plays a key role in suppressing Na dendrite growth. Significantly, the Na metal anodes with the MgF2@RGO aerogel host deliver significantly enhanced Coulombic efficiency and dramatically improved cycling stability for more than 1600 h. The morphology evolution confirms the advantages of the Na metal anode with the MgF2@RGO host, which exhibits dense and flat interfaces. By pairing with the Na3V2(PO4)3 cathode, the Na metal batteries achieve stable cycling and good rate capability, suggesting the potential of the Na/MgF2@RGO anode for practical applications. [ABSTRACT FROM AUTHOR]

Prussian blue analogues (PBAs) have attracted extensive attention as cathode materials in sodium‐ion batteries (SIBs) due to their low cost, high theoretical capacity, and facile synthesis process. However, it is of great challenge to control the crystal vacancies and interstitial water formed during the aqueous co‐precipitation method, which are also the key factors in determining the electrochemical performance. Herein, an antioxidant and chelating agent co‐assisted non‐aqueous ball‐milling method to generate highly‐crystallized Na2‐xFe[Fe(CN)6]y with hollow structure is proposed by suppressing the speed and space of crystal growth. The as‐prepared Na2‐xFe[Fe(CN)6]y hollow nanospheres show low vacancies and interstitial water content, leading to a high sodium content. As a result, the Na‐rich Na1.51Fe[Fe(CN)6]0.87·1.83H2O hollow nanospheres exhibit a high initial Coulombic efficiency, excellent cycling stability, and rate performance via a highly reversible two‐phase transition reaction confirmed by in situ X‐ray diffraction. It delivers a specific capacity of 124.2 mAh g−1 at 17 mA g−1, presenting ultra‐high rate capability (84.1 mAh g−1 at 3400 mA g−1) and cycling stability (65.3% capacity retention after 1000 cycles at 170 mA g−1). Furthermore, the as‐reported non‐aqueous ball‐milling method could be regarded as a promising method for the scalable production of PBAs as cathode materials for high‐performance SIBs. [ABSTRACT FROM AUTHOR]