Ultrathin ammonium vanadate nanoflakes on carbon fiber - A binder-free high-rate capability cathode for aqueous medium zinc ion storage

Aqueous zinc ion batteries (AZIBs) are considered as a promising energy storage system owing to their large-scale, low-cost, and high-safety storage. However, their limited specific capacity and poor long-term stability of electrochemical performance have restricted their further application. Herein, we propose a durable, wide interlayer-structured, ultrathin ammonium vanadate (NH4V4O10: NVO) nanoflake grown on pretreated carbon fibers by hydrothermal method as a cathode material in AZIBs. The NVO delivers a specific capacity of approximately 434 mAh g(-1)(@ 0.5 A g(-1)) and exhibits improved performance compared to a cathode prepared by the conventional method using an organic binder. In addition, the NVO delivers a specific capacity of 140 mAh g(-1) at a higher current density of 20 A g(-1) and retains 83% capacity from the initial cycle with a columbic efficiency of 95%. The ultrathin nature of NVO nanoflakes reduces the diffusion length of the metal ion, hence benefiting its storage. Additionally, the direct growth of NVO on carbon fiber exhibits a strong interaction between the active material and current collector without incorporation of any binder material. The combination of these features enhanced the electrochemical storage of zinc ions in the AZIBs at the higher current density. (C) 2021 Elsevier B.V. All rights reserved.