Controlled construction of polyaniline-modified amorphous vanadium pentoxide composite cathode for high performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) have received widespread attention due to their high safety, low cost, and high energy density. However, challenges of cathode materials such as structural collapse, inadequate electronic conductivity, and sluggish Zn²⁺ diffusion kinetics have limited the development of AZIBs. Herein, amorphous V₂O₅ (a-V₂O₅) is synthesized using a facile precipitation method for large-scale preparation, and decorated with polyaniline (PANI) nanoparticles for surface modification, resulting in the composite structure of a-V₂O₅@PANI. The highly disordered lattice structure and abundant structural defects of a-V₂O₅ provide numerous active sites for Zn²⁺ storage. Moreover, the conductive PANI adsorbs on the surface of a-V₂O₅, which makes up for its inherently poor conductivity and improves the Zn²⁺ diffusion kinetics. In addition, further electrochemical analysis and structure characterization confirm that the a-V₂O₅@PANI is favorable to form a highly active intermediate phase i.e. Zn₃(OH)₂V₂O₇·2H₂O during cycling, which presents excellent electrical conductivity and diffusion kinetics. Furthermore, the a-V₂O₅@PANI cathode exhibits high electrochemical reversibility and structural stability. As a result, the a-V₂O₅@PANI composite achieves an excellent high rate capability of 195.1 mAh g⁻¹ at a current density of 10 A g⁻¹ and a long cycling life with the capacity retention of 88.3 % at a current density of 5 A g⁻¹ after 1000 cycles. This work provides a high-performance cathode material that can be prepared on a large scale for AZIBs and improves the understanding of amorphous vanadium oxides for Zn²⁺ storage.