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Aqueous sodium‐ion batteries (ASIB) offer many potential applications in large‐scale power grids since they are inexpensive, safe, and environmentally friendly. Sodium superionic conductors (NASICON), especially carbon‐coated Na3V2(PO4)3 (NVP), have attracted much attention due to the full use of their high ion migration speed. However, the poor cycle lifespan and capacity retention of NVP hinder its application in ASIB. Herein, a novel bimetal‐doped Na3V1.3Fe0.5W0.2(PO4)3 (NV1.3Fe0.5W0.2P) cathode is designed and synthesized to achieve outstanding cycling stability (95 % of initial capacity at 50th cycle). The electrochemical behavior and charge storage mechanism of NV1.3Fe0.5W0.2P are systematically investigated by various in situ and ex situ characterizations. The Fe and W codoping could stabilize the NASICON framework to suppress the proton attack on the Na site in the aqueous electrolyte, thus resulting in excellent cycling stability. DFT calculations show that bimetallic doping increases the structural stability of NVP. Moreover, an ASIB fabricated using a NV1.3Fe0.5W0.2P cathode and a NaTi2(PO4)3 anode delivers 64 mAh g−1 at room temperature, 95 % capacity retention after 50 cycles (1 A g−1). [ABSTRACT FROM AUTHOR]

Aqueous zinc‐ion batteries (AZIBs) have recently shown promise as prospective energy storage systems owing to their eco‐friendliness, low price, high security, and reversible storage. However, low specific capacity and the lack of cathode materials with a long life severely restrict the development of AZIBs. Herein, nanoflower‐like vanadium oxide nanoribbons are rapidly synthesized using a microwave‐assisted solvothermal method, and the layer spacing of synthesized nanoribbons is subsequently expanded with ammonium via high‐temperature calcination in an NH3 atmosphere. The increased layer spacing of vanadium oxide facilitates the intercalation/extraction of Zn2+ and accelerates the electrochemical kinetics, resulting in a highly reversible pseudocapacitive contribution (71% at a scan rate of 1 mV s−1). The ammonium‐embedded V2O5 with the carbon‐coated NH4V4O10/C (NHVO/C) cathode shows a high specific capacity (458.6 mAh g−1 at 0.1 A g−1) and excellent cycling stability (about 90% capacity retention after 2800 cycles at 10 A g−1), which is superior to most cathode materials for AZIBs. Furthermore, reversible Zn2+ intercalation/extraction in the NHVO/C cathode during electrochemical reactions is elucidated through in situ and ex situ material characterization. The findings are expected to inspire the development of advanced vanadium‐based cathode materials for green, safe, and dependable energy storage devices for commercial applications. [ABSTRACT FROM AUTHOR]

Recently, aqueous zinc‐ion batteries have become a promising candidate for energy storage devices due to their low cost, high capacity, and environmental friendliness. However, the low electrical conductivity and irreversible Zn2+ intercalation/extraction of cathode materials limit the rate performance and cycling stability of Zn‐ion batteries. Herein, carbon‐coated V2O5 nanoflowers with K+ pre‐embedment (KVO‐C) were synthesized by hydrothermal and high‐temperature annealing methods, showing enhanced electrical conductivity and crystallinity. Assembled with Zn anode and 2 M Zn(CF3SO3)2 electrolyte, the optimized KVO‐C3 battery achieves a high specific capacity of 389.2 mAh g−1 at a current density of 0.1 A g−1 and retains 85% even with a 50‐fold increase in current density and cycling back to 0.1 A g−1. KVO‐C3 also shows excellent capacity retention of 77% and coulomb efficiency of nearly 100% after 2000 cycles and delivers a high energy density of 209 Wh kg−1 at a power density of 3500 W kg−1. [ABSTRACT FROM AUTHOR]

Selenide, particularly transition-metal selenide, is gaining popularity for use as electrode materials in electrochemical capacitors, because they are low cost, highly conductive, earth abundant, and environmentally benign. Here, we fabricated (Ni, Cu) Se2 nanowires on nickel foam (NF) with a facile one-pot hydrothermal method. Upon rational design and careful growth control, regular (Ni, Cu) Se2 nanowires of several micrometers in length were grown, having an areal specific capacitance of 5.92 F cm−2 at a current density of 2 mA cm−2. Afterwards, an asymmetric supercapacitor was assembled by selecting the (Ni, Cu) Se2 nanowire/NF as the positive electrode, and reduced graphene oxide (RGO) as the negative electrode, delivering an ultrahigh energy density of 44.46 Wh kg−1 at a power density of 797.9 W kg−1, and when tested at an ultrahigh power density of 9796.7 W kg−1, an energy density of 6.53 Wh kg−1 can be still maintained, evidencing its potential applications. Besides its high energy density features, it is impressive to notice that the energy density still maintains 97.56 % even after 4000-cycle fierce cycling at an ultrahigh current density of 50 mA cm−2. To the best of our knowledge, it is the first-ever reported (Ni, Cu) Se2-based supercapacitor/asymmetric supercapacitor. This work may arouse new interest for designing and growing transition-metal selenide and/or metal selenide for large-scale, practical supercapacitor applications. [ABSTRACT FROM AUTHOR]

A novel and facile one-step method for growing a-phase nickel-cobalt hydroxides is developed. The use of 1-methyl-2-pyrrolidone (NMP) in the mixed solvent plays the decisive role in the precipitation of metal ions and the formation of a-phase hydroxides. The synthetic method is robust enough to synthesize Ni-Co hydroxides with different stoichiometric ratios of Ni and Co, and can be extended to the fabrication of Ni0.67Zn0.33 hydroxide in the a phase. More encouragingly, the method employed can be further used to grow layered nickel-cobalt hydroxides on Ni foam. As the electroactive materials for pseudocapacitors, the Ni-Co hydroxides deliver an ultrahigh specific capacitance (1337.4 Fg-1 at 1 Ag-1 for Ni0.67Co0.33 hydroxide) with improved rate capability and cycling stability. Moreover, a greatly increased specific capacitance (2248.9 and 2286.7 Fg-1 at 1 Ag-1 for Ni0.5Co0.5 and Ni0.67Co0.33 hydroxides, respectively) with superior cycling stability is obtained after growth on Ni foam. [ABSTRACT FROM AUTHOR]

A hedgehog‐like hollow Ni‐Mn precursor with uniform ordered 1D nanostructures is prepared by a facile directional Mn‐induced approach. The Ni‐Mn oxides and sulfides are obtained after thermal treatment and vulcanization for the studied precursor and retain the morphology. The excellent electrochemical performance of the two products has promising potentials for future energy storage systems. [ABSTRACT FROM AUTHOR]

The inside front cover was designed by J. Jiang and co‐workers, whose article is on page 857. The background shows a scanning electron microscopy (SEM) image of Ni‐Mn oxides and sulfides precursors, from which one can see the morphology of these nanoparticles. The highlighted line in the top of the image stresses the hollow nanostructure. The small red particles represent the ions in the electrolyte. The unique 3D open structure of the Ni‐Mn oxides and sulfides buffer the volume strains during the ion electrolyte adsorption/desorption process. Finally, the possible formation process of such directional Mn‐induced synthesis is shown in the bottom right corner. [ABSTRACT FROM AUTHOR]