Youcun Bai,Heng Zhang,Bin Xiang,Xinyue Liang,Jiangyu Hao,Chong Zhu,Lijin Yan
As a typical transition-metal dichalcogenides, vanadium diselenide (VSe2) 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 VSe2 nanosheets with defect (VSe2–x-SS), thereby further improving the conductivity and activity of VSe2–x-SS. Density functional theory calculations confirmed that Se defect can adjust the adsorption energy of Zn2+ ions. This means that the adsorption/desorption process of Zn2+ ions on VSe2–x-SS is more reversible than that on pure SS-supported VSe2 (VSe2-SS). As a result, the Zn//VSe2–x-SS battery showed more excellent electrochemical performance than Zn//VSe2-SS. The VSe2–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 Zn2+ ions in this VSe2–x-SS electrode material. This study provides an effective strategy for the rational design of electrode materials for electrochemical energy-storage devices.
Jean Pierre Mwizerwa,Changyong Liu,Kun Xu,Ning Zhao,Zhangwei Chen,Jun Shen
Surface engineering of transition metal oxide cathode materials for Li-ion batteries is highly important to achieve high-capacity retention, high-rate capability, and long-life term. In this study, VSe 2 nanosheets are prepared and used as a surface sensitizer to enhance the electrochemical properties of LiFePO 4 (LFP) cathode material. The LiFePO 4 @VSe 2 (LFP@VSe 2 ) composite is formed by anchoring 1D-LFP particles with the as-prepared 2D-VSe 2 nanosheets by using an in-situ solution phase technique. When the LFP@VSe 2 composites are used as cathode materials for Li-ion batteries, the Li surface-controlled storage behavior of the batteries is reasonably enhanced. The performance is attributed to the improvement in the inherent Li-ion conductivity of LFP particles, thereby inhibiting surface diffusion drawbacks and decreasing charge transfer resistance. The exterior VSe 2 attached to the LFP serves as a second electrically conducting layer to increase conductivity into the entire electrode. Thus, these conditions enhance the electron transfer kinetics and surface stability of the LFP cathode. LFP@VSe 2 composite cathode exhibits an ultrastable specific capacity of 166.5 mAh g −1 after 100 cycles @ 0.1 C and can retain a specific capacity of 146.7 and 46.5 mAh g −1 after 700 and 2000 cycles respectively at a current rate of 0.3 C and 10 C.
Jian Zhang,Jiandong Li,Huajie Huang,Wei Chen,Yan Cui,Yonghua Li,Weiwei Mao,Xinbao Zhu,Xing'ao Li
Defect engineering of transition metal dichalcogenides (TMDCs) is important for improving electrocatalytic hydrogen evolution reaction (HER) performance. Herein, a facile and scalable atomic-level di-defect strategy over thermodynamically stable VSe 2 nanoflakes, yielding attractive improvements in the electrocatalytic HER performance over a wide electrolyte pH range is reported. The di-defect configuration with controllable spatial relation between single-atom (SA) V defects and single Se vacancy defects effectively triggers the electrocatalytic HER activity of the inert VSe 2 basal plane. When employed as a cathode, this di-defects decorated VSe 2 electrocatalyst requires overpotentials of 67.2, 72.3, and 122.3 mV to reach a HER current density of 10 mA cm −2 under acidic, alkaline, and neutral conditions, respectively, which are superior to most previously reported non-noble metal HER electrocatalysts. Theoretical calculations reveal that the reactive microenvironment consists of two adjacent SA Mo atoms with two surrounding symmetric Se vacancies, yielding optimal water dissociation and hydrogen desorption kinetics. This study provides a scalable strategy for improving the electrocatalytic activity of other TMDCs with inert atoms in the basal plane.
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