Quinone-amine polymers prepared by simple precipitation polymerization and used as cathodes for aqueous zinc-ion batteries and electrochromic materials

Abstract

Zinc-ion batteries (ZIBs) require an investment in organic cathode materials because of their structural diversity and desirable specific capacities. However, low real capacities and poor cycling stabilities can result from the high solubilities of small-molecule organic compounds. Here, poly 2-methyl-5-((4-(phenyl(p-tolyl)amino)phenyl)amino)cyclohexa-2,5-diene-1,4-dione (PQAH) and poly 2,5-dichloro-3-methyl-6-((4-(phenyl(p-tolyl)amino)phenyl)amino)cyclohexa-2,5-diene-1,4-dione (PQACl) were used to design and synthesize qui cathode materials for aqueous ZIBs. Quinone amine polymers (PQAs) polymerised by simple precipitation have large π-conjugated backbones and miltiple active sites. PQAH and PQACl exhibited superior electrochemical characteristics owing to their stable π-conjugated skeletons and abundant active sites. In particular, PQAH exhibited remarkable cycling stability (78.26% capacity retention rate after 10 000 cycles at 5 A g⁻¹), a high specific capacity (203.4 mA h g⁻¹ at 0.1 A g⁻¹) and a high rate. Due to their low LUMO levels and small bandgaps (ΔE), both quinone amine polymers showed strong electrochromic redox activities. The spatial effects of chlorine atoms, which decreased the structural planarities of the conjugates and the effective conjugation lengths, were responsible for the blueshift in the absorption spectrum of PQACl relative to that of PQAH. PQAH showed a relatively wide band gap but was electrochemically more active and had a larger colouring efficiency (CE) (239.9 cm² C⁻¹). The potential of PQAs for use in electrochromic (EC) polymers and aqueous ZIBs is significantly enhanced by this work.