As a typical transition-metal dichalcogenides, vanadium diselenide (VSe 2 ) is a promising electrode material for aqueous zinc-ion batteries due to its metallic characteristics and excellent electronic conductivity. In this work, we propose a strategy of hydrothermal reduction synthesis of stainless-steel (SS)supported VSe 2 nanosheets with defect (VSe 2−x -SS), thereby further improving the conductivity and activity of VSe 2−x -SS. Density functional theory calculations confirmed that Se defect can adjust the adsorption energy of Zn 2+ ions. This means that the adsorption/desorption process of Zn 2+ ions on VSe 2−x -SS is more reversible than that on pure SS-supported VSe 2 (VSe 2 -SS). As a result, the Zn// VSe 2−x -SS battery showed more excellent electrochemical performance than Zn// VSe 2 -SS. The VSe 2−x -SS electrode shows a good specific capacity of 265.2 mA h g −1 (0.2 A g −1 after 150 cycles), satisfactory rate performance, and impressive cyclic stability. In addition, we also have explored the energy-storage mechanism of Zn 2+ ions in this VSe 2−x -SS electrode material. This study provides an effective strategy for the rational design of electrode materials for electrochemical energy-storage devices.

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Electrochemical activation can be appropriate for constructing tunable/controllable defects within the interior of electrode materials. However, the activation mechanisms under different applied electric fields urgently need to be systematically explored. Herein, the electrochemically activated manganese dioxide (MnO 2 ) samples are prepared via applying a positive/negative electric field, and two different activation mechanisms are revealed through a series of characterization methods. During the activation process, it is fascinating to discover that MnO 2 mainly generates the O vacancies under positive voltage, whereas the electrolyte cations are embedded in the interlayer under negative voltage. The generated O vacancies and intercalated ions not only act as active sites or participate in the charge-transport process, but also enhance the transmission capability of carriers. In contrast, the specific capacitances of optimized MnO 2 samples are 2.9 and 2.8 times than that of pure-MnO 2 after electrochemical activation under positive and negative voltage, respectively. In addition, the activated samples exhibit excellent cycle stability and resistance to electrochemical corrosion, which can well-maintain the 3D network structure composed of nanosheets after 5000 cycles. This strategy opens up a promising approach for exploring efficient and corrosion-resistant electrode materials.

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