Dual mechanism with graded energy storage in long-term aqueous zinc-ion batteries achieved using a polymer/vanadium dioxide cathode

Composite materials based on vanadium oxides have been widely used in aqueous zinc-ion batteries (AZIBs). However, due to the low energy storage activity of ligand materials, composite electrodes face application bottlenecks such as low specific capacity and insufficient efficiency. To fully utilize the various components, a novel redox couple (I-/I0) reaction is carried out in AZIBs utilizing the functional ligand materials. Herein, a 1,5-naphthalenediamine (NDA)-composited VO2 hierarchical material (VO@NDA) with both iodine and zinc storage activity is proposed, which can be regarded as an innovative concept for designing high specific energy batteries. The internal VO2 provides zinc storage ability while the amino functional group in the outer NDA acts as an electron donor and neutralizes the electron acceptor I2, facilitating iodine storage. In addition, the low solubility of NDA can also effectively protect VO2 from dissolution in electrolyte. The VO@NDA electrode exhibits dual-high electrochemical performance (10 A g-1, 241 mA h g-1) and outstanding cycling stability (0.017 parts per thousand per cycles at 10 A g-1). The positive role of NDA in iodine storage was investigated via electrochemical tests and ex/in situ characterization, which provided the direction for constructing advanced multi-ion energy storage electrodes. The functional groups on NDA can fix the iodine produced in the oxidation process, forming a graded energy storage structure.