Recently, room-temperature stationary sodium-ion batteries (SIBs) have received extensive investigations for large-scale energy storage systems (EESs) and smart grids due to the huge natural abundance and low cost of sodium. The SIBs share a similar "rocking-chair" sodium storage mechanism with lithium-ion batteries; thus, selecting appropriate electrodes with a low cost, satisfactory electrochemical performance, and high reliability is the key point for the development for SIBs. On the other hand, the carefully chosen elements in the electrodes also largely determine the cost of SIBs. Therefore, earth-abundantmetal-based compounds are ideal candidates for reducing the cost of electrodes. Among all the high-abundance and low-cost metal elements, cathodes containing iron and/or manganese are the most representative ones that have attracted numerous studies up till now. Herein, recent advances on both ironand manganese-based cathodes of various types, such as polyanionic, layered oxide, MXene, and spinel, are highlighted. The structure-function property for the iron-and manganese-based compounds is summarized and analyzed in detail. With the participation of iron and manganese in sodium-based cathode materials, real applications of room-temperature SIBs in large-scale EESs will be greatly promoted and accelerated in the near future.

It is highly desired but still remains challenging to design and develop a Co-based nanoparticle-encapsulated conductive nanoarray at room temperature for high-performance water oxidation electrocatalysis. Here, it is reported that room-temperature anodization of a Co(TCNQ) (TCNQ = tetracyanoquinodimethane) nanowire array on copper foam at alkaline pH leads to in situ electrochemcial oxidation of TCNQ into water-insoluable TCNQ nanoarray embedding Co(OH) nanoparticles. Such Co(OH) -TCNQ/CF shows superior catalytic activity for water oxidation and demands only a low overpotential of 276 mV to drive a geometrical current density of 25 mA cm in 1.0 m KOH. Notably, it also demonstrates strong long-term electrochemical durability with its activity being retrained for at least 25 h, a high turnover frequency of 0.97 s at an overpotential of 450 mV and 100% Faradic efficiency. This study provides an exciting new method for the rational design and development of a conductive TCNQ-based nanoarray as an interesting 3D material for advanced electrochemical applications.

A Mn-based NASICON-type Na 4 VMn(PO 4 ) 3 cathode is considered to be one of the most promising substitutions for Na 3 V 2 (PO 4 ) 3 due to the huge abundance and appropriate redox potential from Mn. However, the current Na 4 VMn(PO 4 ) 3 /C cathode still delivers a limited electrochemical performance due to the sluggish kinetics and negative structural degradation caused by the Mn in the structure. Herein, a selective replacement of vanadium rather than manganese in the Na 4 VMn(PO 4 ) 3 system was developed to fully utilize the manganese element and enhance the structural stability. Both experimental and calculation results affirmed that the Al-substituted Na 4 V 0.8 Al 0.2 Mn(PO 4 ) 3 cathode shows favorable Na + kinetics and structure stability. The resulting Na 4 V 0.8 Al 0.2 Mn(PO 4 ) 3 reveals a discharge capacity of ∼84 mA h g −1 at 40 C and renders a capacity retention of 92% after cycling 1000 times at 5 C. Inspired by the availability of Al dopants, we also demonstrated the Al-doped Mn-richer Na 4.2 V 0.6 Al 0.2 Mn 1.2 (PO 4 ) 3 to be a viable candidate for Mn-rich phosphate cathodes.

Capacity fading induced by unstable surface chemical properties and intrinsic structural degradation is a critical challenge for the commercial utilization of Ni-rich cathodes. Here, a highly stabilized Ni-rich cathode with enhanced rate capability and cycling life is constructed by coating the molybdenum compound on the surface of LiNi 0.815 Co 0.15 Al 0.035 O 2 secondary particles. The infused Mo ions in the boundaries not only induce the Li 2 MoO 4 layer in the outermost but also form an epitaxially grown outer surface region with a NiO-like phase and an enriched content of Mo 6+ on the bulk phase. The Li 2 MoO 4 layer is expected to reduce residential lithium species and promote the Li + transfer kinetics. The transition NiO-like phase, as a pillaring layer, could maintain the integrity of the crystal structure. With the suppressed electrolyte−cathode interfacial side reactions, structure degradation, and intergranular cracking, the modified cathode with 1% Mo exhibits a superior discharge capacity of 140 mAh g −1 at 10 C, a superior cycling performance with a capacity retention of 95.7% at 5 C after 250 cycles, and a high thermal stability.

great significance to develop electrochemical energy-storage technique and take advantage of sustainable and renewable energy. [1][2][3][4][5][6][7] Owing to natural abundance, wide availability, and low cost of sodium resources, sodium-ion batteries (SIBs) have been considered as one of most fascinating alternatives to the well-commercialized lithium-ion batteries for future large-scale stationary energy-storage systems with high adaptability and energy efficiency. [8][9][10][11][12][13] To develop satisfactory electrode materials in the future development of SIBs, continued research efforts have been devoted to screen new cathodes over the past few years. [14][15][16][17][18][19] Among a wide variety of cathode candidates including layered oxides, polyanion compounds, and Prussian blue analogues, layered oxide cathode materials have received significant attention because of the high voltage, low cost, and simple synthesis. Recently, research has made dramatic progress especially on manganese-based layered oxides such as zinc-doped Na 0.833 [Li 0.25 Mn 0.75 ]O 2 , Na 0.7 Mg 0.05 [Mn 0.6 Ni 0.2 Mg 0.15 ]O 2 , and Na 2.3 Cu 1.1 Mn 2 O 7−δ , which open new opportunities for developing high-performance cathode materials. [20][21][22][23][24] However, typical P2-type Na 2/3 Ni 1/3 Mn 2/3 O 2 cathode material As one of the most promising cathode candidates for room-temperature sodium-ion batteries (SIBs), P2-type layered oxides face the challenge of simultaneously realizing high-rate performance while achieving long cycle life. Here, a stable Na 2/3 Ni 1/6 Mn 2/3 Cu 1/9 Mg 1/18 O 2 cathode material is proposed that consists of multiple-layer oriented stacking nanoflakes, in which the nickel sites are partially substituted by copper and magnesium, a characteristic of the material that is confirmed by multiscale scanning transmission electron microscopy and electron energy loss spectroscopy techniques. Owing to the optimal morphology structure modulation and chemical element substitution strategy, the electrode displays remarkable rate performance (73% capacity retention at 30C compared to 0.5C) and outstanding cycling stability in Na half-cell system couple with unprecedented full battery performance. The underlying thermal stability, phase stability, and Na + storage mechanisms are clearly elucidated through the systematical characterizations of electrochemical behaviors, in situ X-ray diffraction at different temperatures, and operando X-ray diffraction upon Na + deintercalation/intercalation. Surprisingly, a quasi-solid-solution reaction is switched to an absolute solid-solution reaction and a capacitive Na + storage mechanism is demonstrated via quantitative electrochemical kinetics calculation during charge/discharge process. Such a simple and effective strategy might reveal a new avenue into the rational design of excellent rate capability and long cycle stability cathode materials for practical SIBs.

Considering the ever‐growing climatic degeneration, sustainable and renewable energy sources are needed to be effectively integrated into the grid through large‐scale electrochemical energy storage and conversion (EESC) technologies. With regard to their competent benefit in cost and sustainable supply of resource, room‐temperature sodium‐ion batteries (SIBs) have shown great promise in EESC, triumphing over other battery systems on the market. As one of the most fascinating cathode materials due to the simple synthesis process, large specific capacity, and high ionic conductivity, Na‐based layered transition metal oxide cathodes commonly suffer from the sluggish kinetics, multiphase evolution, poor air stability, and insufficient comprehensive performance, restricting their commercialization application. Here, this review summarizes the recent advances in layered oxide cathode materials for SIBs through different optimal structure modulation technologies, with an emphasis placed on strategies to boost Na+ kinetics and reduce the irreversible phase transition as well as enhance the store stability. Meanwhile, a thorough and in‐depth systematical investigation of the structure–function–property relationship is also discussed, and the challenges as well as opportunities for practical application electrode materials are sketched. The insights brought forward in this review can be considered as a guide for SIBs in next‐generation EESC.

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As one of the most promising cathodes for rechargeable sodium-ion batteries (SIBs), O3-type layered transition metal oxides commonly suffer from inevitably complicated phase transitions and sluggish kinetics. Here, a Na[Li Ni Mn Cu Mg ]O cathode material with the exposed {010} active facets by multiple-layer oriented stacking nanosheets is presented. Owing to reasonable geometrical structure design and chemical substitution, the electrode delivers outstanding rate performance (71.8 mAh g and 16.9 kW kg at 50C), remarkable cycling stability (91.9% capacity retention after 600 cycles at 5C), and excellent compatibility with hard carbon anode. Based on the combined analyses of cyclic voltammograms, ex situ X-ray absorption spectroscopy, and operando X-ray diffraction, the reaction mechanisms behind the superior electrochemical performance are clearly articulated. Surprisingly, Ni /Ni and Cu /Cu redox couples are simultaneously involved in the charge compensation with a highly reversible O3-P3 phase transition during charge/discharge process and the Na storage is governed by a capacitive mechanism via quantitative kinetics analysis. This optimal bifunctional regulation strategy may offer new insights into the rational design of high-performance cathode materials for SIBs.