Dual modulation of homogeneous nanomaterialization and electrochemical activation enhancing zinc ion storage

Abstract

Vanadium-based electrode materials are widely investigated, but the low specific capacity and slow electrochemical kinetics in aqueous zinc-ion batteries still limit their commercial development. Herein, the VS₂/CaV₄O₉ material with the morphology of nanoflower was synthesized by a one-step hydrothermal method. Compared to the blocky structure of pure VS₂ material, the VS₂/CaV₄O₉ material is composed of thinner homogeneous nanosheets. The open structures could provide abundant electrochemical active sites and ion transport channels, and then promote the electrochemical reaction kinetics. In addition, they can also buffer the bulk strain during the reaction process. To improve the utilization of vanadium elements, an in-situ electrochemical activation strategy is used to explore the storage performance of the VS₂/CaV₄O₉ material, the different activation voltage range of 0.4–1.6 and 0.4–1.4 V are selected, respectively. Compared with the longer activation plateau of activated-VS₂, the VS₂/CaV₄O₉ cathode could quickly reach the activation state in the range of 1.4–1.6 V and cause the release of additional Zn storage sites simultaneously. The VS₂/CaV₄O₉ cathode delivers a higher power density of 37,000 W kg⁻¹ and a significant energy density of 423 Wh kg⁻¹. At the high current density of 15 A g⁻¹, the VS₂/CaV₄O₉ cathode still has a discharge capacity of 183.9 mAh g⁻¹ after 5,000 cycles, and the capacity decay rate per cycle is only 0.0042%. Continuous cyclic voltammetry (CV) curves, electrochemical impedance spectroscopy (EIS) measurements, density functional theory (DFT) calculation and galvanostatic intermittent titration technique (GITT) measurements demonstrate that the VS₂/CaV₄O₉ cathode has a faster ion diffusion/charge transfer kinetics. Meanwhile, the assembled flexible device has an excellent mechanical stability.