The realizing of high‐performance rechargeable aqueous zinc‐ion batteries (ZIBs) with high energy density and long cycling life is promising but still challenging due to the lack of suitable layered cathode materials. The work reports the excellent zinc‐ion storage performance as‐observed in few‐layered ultrathin VSe2 nanosheets with a two‐step Zn2+ intercalation/de‐intercalation mechanism verified by ex situ X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) characterizations. The VSe2 nanosheets exhibit a discharge plateau at 1.0–0.7 V, a specific capacity of 131.8 mAh g−1 (at 0.1 A g−1), and a high energy density of 107.3 Wh kg−1 (at a power density of 81.2 W kg−1). More importantly, outstanding cycle stability (capacity retention of 80.8% after 500 cycles) without any activation process is achieved. Such a prominent cyclic stability should be attributed to its fast Zn2+ diffusion kinetics (DZn2+ ≈ 10−8 cm−2 s−1) and robust structural/crystalline stability. Density functional theory (DFT) calculation further reveals a strong metallic characteristic and optimal zinc‐ion diffusion pathway with a hopping energy barrier of 0.91 eV. The present finding implies that 2D ultrathin VSe2 is a very promising cathode material in ZIBs with remarkable battery performance superior to other layered transitional metal dichalcogenides.

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2D materials with atomically precise thickness and tunable chemical composition hold promise for potential applications in nanoenergy. Herein, a bilayer-structured VOPO 4 ⋅2H 2 O (bilayer-VOP) nanosheet is developed with high-concentration oxygen vacancies ([Vo˙˙]) via a facile liquid-exfoliation strategy. Galvanostatic intermittent titration technique study indicates a 6 orders of magnitude higher zinc-ion coefficient in bilayer-VOP nanosheets (4.6 × 10 −7 cm −2 s −1 ) compared to the bulk counterpart. Assistant density functional theory (DFT) simulation indicates a remarkably enhanced electron conductivity with a reduced bandgap of ≈0.2 eV (bulk sample: 1.5 eV) along with an ultralow diffusion barrier of ≈0.08 eV (bulk sample: 0.13 eV) in bilayer-VOP nanosheets, thus leading to superior diffusion kinetics and electrochemical performance. Mott-Schottky (impedance potential) measurement also demonstrates a great increase in electronic conductivity with ≈57-fold increased carrier concentration owing to its high concentration [Vo˙˙]. Benefited by these unique features, the rechargeable zinc-ion battery composed of bilayer-VOP nanosheets cathode exhibits a remarkable capacity of 313.6 mAh g −1 (0.1 A g −1 ), an energy density of 301.4 Wh kg −1 , and a prominent rate capability (168.7 mAh g −1 at 10 A g −1 ).

Layered vanadium phosphate (VOPO4•2H2O) is reported as a promising cathode material for rechargeable aqueous Zn2+ batteries (ZIBs) owing to its unique layered framework and high discharge plateau. However, its sluggish...

Oxygen evolution electrocatalysts are central to overall water splitting, and they should meet the requirements of low cost, high activity, high conductivity, and stable performance. Herein, a general, selenic‐acid‐assisted etching strategy is designed from a metal–organic framework as a precursor to realize carbon‐coated 3d metal selenides MmSen (Co0.85Se1−x, NiSe2−x, FeSe2−x) with rich Se vacancies as high‐performance precious metal‐free oxygen evolution reaction (OER) electrocatalysts. Specifically, the as‐prepared Co0.85Se1−x@C nanocages deliver an overpotential of only 231 mV at a current density of 10 mA cm−2 for the OER and the corresponding full water‐splitting electrolyzer requires only a cell voltage of 1.49 V at 10 mA cm–2 in alkaline media. Density functional theory calculation reveals the important role of abundant Se vacancies for improving the catalytic activity through improving the conductivity and reducing reaction barriers for the formation of intermediates. Although phase change after long‐term operation is observed with the formation of metal hydroxides, catalytic activity is not obviously affected, which strengthens the important role of the carbon network in the operating stability. This study provides a new opportunity to realize high‐performance OER electrocatalysts by a general strategy on selenic acid etching assisted vacancy engineering.