Quinone-amine polymer nanospheres with enhanced redox activity for aqueous proton storage

One of the biggest obstacles to the development of aqueous proton batteries (APBs), despite numerous optimization techniques, is the preparation and use of high-performance electrode materials. In this work, to improve the high solubility, limited capacity and poor cycle life of small organic molecules in APBs, homogeneous dispersed quinone-amine polymer nanospheres (PQANS) (average diameter: 220 nm) were synthesized by a polymerization reaction based on 3,3'-diaminobenzidine (DAB) and benzoquinone (BQ), making them suitable for proton storage in aqueous systems. As an anode for APBs, the obtained PQANS exhibits an improved reversible capacity of 126.2 mAh/g at 1 A/g after 300 cycles. The durable stable measurement of PQANS at 10 A/g was also conducted with a specific capacity of 66.8 mAh/g after 12,000 cycles. A series of in situ or ex situ measurements were used to establish the superior H⁺ storage mechanism of PQANS. A novel reaction mechanism of redox enhancement was revealed due to the existence of more carbonyl groups after the first cycle. Theoretical calculations were conducted to help illustrate the principle of binding protons with functional groups in PQANS. Finally, a PQANS anode-based aqueous proton full battery was constructed to demonstrate its potential application, which exhibits a specific capacity of 50.6 mAh/g at 1 A/g (600 cycles). This work provides a reference for preparing high-performance polymer-based electrode materials in aqueous batteries.