Self-standing poly(benzoquinone–phenylenediamine) hybrid films as binder-free cathodes for aqueous Zn–ion batteries

Quinone polymer-based self-standing films utilized as the binder-free cathodes of aqueous zinc–ion batteries (AZIBs) possess the remarkable features of longer lifespan and higher rate performance in comparison with traditional slurry electrodes, yet their fabrication remains challenging. Here, we have integrated engineering of polymer nanocomposites and film construction to provide a hybrid film of poly(benzoquinone–phenylenediamine) (PQPDA) for advanced binder-free cathodes of AZIBs. First, a two-dimensional (2D) composite material of graphene nanosheet@PQPDA (GNS@PQPDA) is synthesized by the interfacial polymerization method, in which the π–π interaction between GNS and PQPDA enables a tight coating of the polymer on the surfaces of GNS. This unique 2D nanostructure is beneficial to exposing more active sites, enhancing electron transfer, providing fast ion diffusion and buffering the volume variation. Owing to the synergistic effect of PQPDA coating and highly conductive CNT, the GNS@PQPDA nanosheets demonstrate highly competitive charge storage performance: a high reversible capacity of 155.5 mAh g −1 at 0.1 A g −1 (based on the overall mass of GNS@PQPDA) and a fast rate capability of 93.8 mAh g −1 at 5 A g −1 . Second, a hybrid film of GNS@PQPDA–carbon nanotube–reduced graphene oxide (GNS@PQPDA–CNT–rGO) is constructed via vacuum filtration and hydroiodic (HI) acid reduction. The film is employed as a binder-free cathode to assemble the Zn//GNS@PQPDA–CNT–rGO battery, which exhibits large specific capacity (120.7 mA h g −1 at 0.1 A g −1 , based on the overall mass of GNS@PQPDA–CNT–rGO) and long–term cycling stability (82.6% of the initial capacity after 2000 cycles at 1 A g −1 ). This study provides an effective method to fabricate quinone polymer-based self-standing films as the binder-free cathodes of AZIBs.