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For cost and safety reasons, aqueous batteries are suitable for large-scale energy storage. Among all aqueous batteries, the rechargeable aqueous zinc ion batteries (ZIBs) are promising choices owing to the low equilibrium potential and high volumetric capacity of zinc. However, its development is also severely hindered by the limited available cathode materials, which generally display poor cycling capabilities. As one of the most investigated POVs (polyvanadates) today, (V 10 O 28)6− has been demonstrated to be feasible in the energy storage rely on the well-defined structure and fascinating material activity. Herein, we propose a polyvanadate-Na 6 V 10 O 28 with (V 10 O 28)6− anion as a support structure and serve it for the first time as aqueous ZIBs cathode. The high stability of the (V 10 O 28)6− cluster permits the material to tolerate the reversible (de)insertion of Zn2+. As a result, the Na 6 V 10 O 28 cathode delivers a high capacity of 279.5 mAh g−1 and extraordinary lifespan over 2000 cycles. Furthermore, the pseudocapacitance analysis and GITT test reveal the pseudocapacitance behavior and high Zn2+ diffusion coefficient (10−10 cm2 s−1) of the Na 6 V 10 O 28 /Zn cell, respectively. Not only that, ex-situ XRD, XPS, and TEM are also employed to analyze the storage mechanism of Zn2+, indicating the synergistic Zn-storage capacity of Na 6 V 10 O 28 and irreversible products. Overall, this work presents new insights into the application of Na 6 V 10 O 28 in aqueous ZIBs and also demonstrates the competitive potential of POVs for energy storage. [Display omitted] • For the first time, the Na 6 V 10 O 28 cathode is applied for aqueous zinc ion batteries. • Na 6 V 10 O 28 delivers excellent cycling stability and the high specific discharge capacity. • The Zn2+ ion diffusion rate of Na 6 V 10 O 28 is as high as 10−10 cm2 s−1. • The high reversibility of Zn2+ insertion/extraction in Na 6 V 10 O 28 is demonstrated by ex-situ XRD. For cost and safety reasons, aqueous batteries are suitable for large-scale energy storage. Among all aqueous batteries, rechargeable aqueous zinc-ion batteries (ZIBs) are promising choices owing to the low equilibrium potential and high volumetric capacity of zinc. However, its development is also severely hindered by the limited available cathode materials, which generally display poor cycling capabilities. As one of the most investigated POVs (polyvanadates) today, (V 10 O 28)6− has been demonstrated to be feasible in energy storage rely on the well-defined structure and fascinating material activity. Herein, we propose a polyvanadate-Na 6 V 10 O 28 with (V 10 O 28)6− anion as a support structure and serve it for the first time as an aqueous ZIBs cathode. The high stability of the (V 10 O 28)6− cluster permits the material to tolerate the reversible (de)insertion of Zn2+. As a result, the Na 6 V 10 O 28 cathode delivers a high capacity of 279.5 mAh g−1 after activation and an extraordinary lifespan over 2000 cycles. Furthermore, the pseudocapacitance analysis and GITT test reveal the pseudocapacitance behavior and high Zn2+ diffusion coefficient (10−10 cm2 s−1) of the Na 6 V 10 O 28 /Zn cell, respectively. Not only that, ex-situ XRD, XPS, and TEM are also employed to analyze the storage mechanism of Zn2+, indicating the synergistic zinc-storage capacity of Na 6 V 10 O 28 and irreversible products. Overall, this work presents new insights into the application of Na 6 V 10 O 28 in aqueous ZIBs and also demonstrates the competitive potential of POVs for energy storage. [ABSTRACT FROM AUTHOR]

• NVO are prepared using Pluronic-F127 as structure-directing agent. • NVO show unique nanorod structures. • NVO calcined at 400 °C shows high capacity and high rate capability. • Kinetics analysis verifies the pseudocapacitive behavior of R-400. • Outstanding performance is attributed to low resistance and fast Na+ ions intercalation/deintercalation kinetics. In this study, NaV 3 O 8 nanorods are successfully prepared using nonionic surface-active agents Pluronic-F127 as structure-directing agent. The as-prepared NaV 3 O 8 nanorods calcinated at different temperatures are characterized by various techniques, including X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy. The NaV 3 O 8 calcinated at 400 °C for 20 h shows appropriate sizes and uniform morphologies of the nanorods, 4–7 μm in length and 0.2–0.5 μm in diameter. The NaV 3 O 8 nanorods as cathode materials for Na-ion batteries deliver high discharge capacity reaching up 110.4 mAh g−1 at current density of 120 mA g−1, as well as long lifespan by maintaining capacity of 162.1 mAh g−1 after 500 charge-discharge cycles. Also, a high reversible capacity of 83.9 mAh g−1 can be retained after 500 cycles at high rate of 2 A g−1. The obtained outstanding electrochemical performances are associated with the unique micro-nano structures, which does not only facilitate transport of Na+ ion, but also resist erosion from electrolytes. Overall, the results suggest the promise of NaV 3 O 8 nanorods as cathode materials for high capacity, high power and long lifespan Na-ion batteries. This work may open an innovative route to discover diverse electrode materials with nanostructure for energy storage system. [ABSTRACT FROM AUTHOR]

• 1. For the first time, the Li 7 [V 15 O 36 (CO 3)] and γ -LiV 2 O 5 as host materials to store Zn2+. • 2. A larger voltage window (0.2–1.9 V) than most other aqueous zinc ion batteries. • 3. The energy density and power density of the Li 7 [V 15 O 36 (CO 3)] and the γ -LiV 2 O 5 is high. • 4. The Zn2+ storage mechanisms of the Li 7 [V 15 O 36 (CO 3)] and the γ -LiV 2 O 5 are proved. Recently, many reports have been published about polyoxovanadates (POVs) with multiple electrons redox activity for energy storage. However, they are easily transformed into solid-state oxides after calcination. We noted that although dehydrated Li 7 [V 15 O 36 (CO 3)] (Li 7 V 15) exhibited a high capacity for lithium-ion batteries (LIBs), it was reported that the electrochemical behavior of the dehydrated sample same as γ -LiV 2 O 5 (γ -LVO) which prepared by annealing the cluster and undehydrated Li 7 V 15 was not redox-active. Interestingly, we were surprised to find that undehydrated Li 7 V 15 and its derivative γ -LVO showed better electrochemical performance than LIBs when first proposed as the cathode to store Zn2+. Both Li 7 V 15 and γ -LVO electrodes provided excellent rate performance and satisfied cyclability (135.0 and 214.1 mAh g−1 at 3 A g−1 after 1000 cycles, respectively). The fast kinetics of Li 7 V 15 and γ -LVO were verified by pseudocapacitive analysis, GITT and EIS tests. Moreover, the Zn2+ storage mechanism and redox behavior of Li 7 V 15 and γ -LVO were examined by ex-situ measurements. First-principles calculations revealed that the Zn2+ was chemisorbed on the clusters and physisorbed between the clusters. This work enriches the POVs cathode chemistry in aqueous energy storage. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • ZIF-8 nanocubes are rapidly synthesized and adjusted in aqueous solution. • ZnSe nanoparticles embedded N-doped carbon nanocubes (ZS-NP@NC) are first prepared. • ZS-NP@NC-600 displays high discharge capacity and excellent cyclability. • Kinetics analysis confirms the pseudocapacitive behavior of ZS-NP@NC. Abstract ZnSe is regarded as a promising anode material for reversible Li-ion batteries because of its high theoretical capacity. Herein, we report a facile chemical precipitation method to controllably synthesize ZIF-8 nanocubes and then select them as sacrificial templates to prepare ZnSe nanoparticles embedded N-doped carbon nanocubes. The as-obtained ZnSe/carbon nanocomposite at 600 °C demonstrates a high initial discharge capacity of 1170.8 mAh g−1 with the initial columbic efficiency of 68.8% at the current density of 0.1 A g−1 in the voltage range of 0.01–3 V. In addition, it displays a reversible capacity of 1166.6 mAh g−1 after 500 cycles at the current density of 0.5 A g−1, indicating the excellent cyclic stability for the designed composites. The enhanced electrochemical performance can be ascribed to its high specific surface area (493.45 m2 g−1) and unique mesoporous structure, which provides efficient Li+ transport channels and additional storage sites. Furthermore, the existence of faradaic pseudocapacitance in ZnSe/carbon nanocomposites also affords additional capacity and contributes to the increased capacity with respect to charge/discharge cycle number. [ABSTRACT FROM AUTHOR]

• The yield and nitrogen content of APO treated biochar increased by 18.8% and 56.8%. • Hierarchical pore structures of biochar were significantly enhanced by air pre-oxidation. • Air pre-oxidation treated biochar shows excellent adsorption capacity as high as 437.8 mg/g towards toluene. In this study, high yield Nitrogen (N)-doped porous biochar for enhanced toluene adsorption was developed via a novel air pre-oxidation (APO) treatment. Stillage and ammonium phosphate were used as the carbon precursor and in situ nitrogen additive, respectively. A range of APO conditions, including temperature (150–400 °C), air flow rate (0–240 mL/min) and time (0.5–3.0 h) were explored for biochar production. The optimized biochar exhibited high yield (55.5%), N content (6.51 at%), surface area (762.9 m2/g) and pore volume (0.444 cm3/g), which significantly exceeded biochar produced without APO. The toluene adsorption capacity of APO treated biochar reached 437.8 mg/g, which was significantly higher than that produced without APO (296.4 mg/g). APO treatment improved the structural characteristics and surface chemistry of biochar, thereby improving its adsorption properties. Possible mechanisms were also discussed for both the APO induced biochar preparation process and toluene adsorption by APO treated biochar. [ABSTRACT FROM AUTHOR]