Naphthoquinone-Based Composite Cathodes for Aqueous Rechargeable Zinc-Ion Batteries

Conventional organic batteries suffer from rapid capacity fading. Organic compounds are inclined to dissolve in the electrolyte and limit the long-term cycling performance of lithium-organic batteries. Carbon skeletons show efficacy in confining the active materials of organic cathodes. In this study, we investigate the electrochemical performance of aqueous zinc-ion batteries with binder-free composite cathodes consisting of carbon nanotubes (CNTs) and naphthoquinone (NQ)-based organics. The quinones are trapped in the nanoporous structure of the CNT framework, and thus the dissolution was minimized. The composite cathodes show stable and high rate cyclability, owing to the high electrical conductivity and confinement of the CNT network. The NQ composite cathode exhibits an initial capacity of 333.5 mAh g^-1, close to the theoretical capacity of 339.0 mAh g^-1. Furthermore, it is uncovered that modifying NQ with functional groups significantly impacts the electrochemical behavior, including the redox potential and capacity retention. With the electron-withdrawing or electron-donating groups, dichlone and 2-((4-hydroxyphenyl) amino) naphthalene-1,4-dione (APh-NQ) show better performance than NQ with improved capacity retention from 41.0 to 70.9 and 68.3%, respectively, after 1000 cycles. The work promotes the development of binder-free organic cathodes for the aqueous Zn-ion batteries and sheds light on designing high-performance electrodes for low-cost energy storage systems.