A Composite Material with Internal Hydrophilicity and External Stability as the Cathode of Aqueous Zinc-Ion Batteries Exhibiting Excellent Rate Performance and Energy Density at High Power Density

Owing to their outstanding safety and low cost, aqueous zinc-ion batteries (ZIBs) are very suitable for large-scale energy storage in the future. However, slow transport dynamics and an unstable host structure are the main barriers that obstruct the evolution of superior cathode materials for high-performance ZIBs. We used glycerol and sodium dodecyl benzene sulfonate (SDBS) as reducing agents and surfactants to produce sea urchinlike VO2 and then coated reduced graphene oxide (rGO) to construct composite materials VO2-SDBS@rGO. The addition of glycerol can not only cause the structural transformation of raw material V2O5 while being reduced, but also provide a large number of hydrophilic groups. At the same time, SDBS leads to the material directional polymerization and produces abundant point defects, which can provide plentiful active sites for ion diffusion. In addition, the coating of rGO further stabilizes the structure of the material and improves the conductivity of the material. When VO2-SDBS@rGO is used as the cathode for aqueous ZIBs, it shows an extraordinary electrochemical performance with a reversible capacity of 437.8 mA h g(-1) at 0.5 A g(-1) and exceptional rate capability (402.8 mA h g(-1) at 10 A g(-1) and 333.8 mAh g(-1) at 32 A g(-1)). After 500 cycles at a current density of 8 A g(-1), the composite VO2-SDBS@rGO can still provide a reversible capacity retention rate of 79.8%. Furthermore, ZIBs using VO2-SDBS@ rGO as the cathode can achieve favorable energy density (307.3 Wh kg(-1)) at high power density (7629 W kg(-1)).

Automated summary

By using glycerol and SDBS as reducing agents and surfactants, sea urchinlike VO2 coated with rGO composite material VO2-SDBS@rGO was produced. When used as the cathode for aqueous ZIBs, this composite material showed extraordinary electrochemical performance with high reversible capacity and exceptional rate capability. After 500 cycles, the reversible capacity retention rate remained as high as 79.8%.