Organic Nanosheets of Imide-Linked Cathodes for High-Performance Aqueous Zinc-Ion Batteries

Organic electrodes have been identified as promising energy-storage materials for aqueous zinc-ion batteries (AZIBs). Small molecular materials have ideal redox properties, high specific capacity, and structural diversity, making them a category of cathode candidates for AZIBs. However, the instability and dissolution during the extraction and insertion of H+/Zn2+ limit their application of the long-cycle stability for AZIBs. Herein, a small-molecule nanosheet (NI-DAQ, ∼14 nm in thickness) with imide linkage is designed and synthesized by the condensation of anthraquinones and anhydrides. It not only inhibits the dissolution of monomer electrodes but also boosts the reactivity and conductivity of the whole molecule by the introduction of π-conjugated imide groups and extended aromatic planes. Therefore, the NI-DAQ electrode obtains a large initial capacity of 191.9 mA h g–1 at 50 mA g–1 and superior cyclability after 3000 cycles at 500 mA g–1 with a minor average capacity fading rate of 0.01% per cycle. Moreover, in situ Fourier transform infrared (FT-IR) and ex situ X-ray photoelectron spectroscopy (XPS) characterization techniques have been implemented to investigate the redox mechanism of C═O units in AZIBs for the NI-DAQ electrode. Thus, a promising conductive molecule is developed and explored in this paper, which can provide insights into the application of organic materials in AZIBs.