High-voltage and highly reversible redox chemistry of in situ cross-linked polydiphenylamine as an aqueous zinc battery cathode

Organic redox-active materials are promising electrode candidates for the next generation of rechargeable batteries owing to their versatile redox chemistry, sustainability, and potential low cost. Here, we present polydiphenylamine as a moderately high voltage (1.25 V vs. Zn) and highly reversible organic cathode for aqueous zinc batteries. As revealed by cyclic voltammetry and spectroscopic analysis, the chemical oxidation-derived diphenylamine dimer electrochemically transforms into a cross-linked polymeric material during the first electrochemical oxidation (charge), which then operates by p-doping/de-doping redox of the amine center and a pseudocapacitor like solid-state charge storage mechanism during the subsequent discharge-charge cycles. With an 80 weight% active loading, the polymer cathode delivers a specific capacity of 138 mAh g -1 at 100 mA g -1 with 73% retention over 1000 cycles at 99.8% Coulombic efficiency. Excellent rate capability is evidenced by 87 mAh g -1 capacity at 400 mA g -1 and highly stable cycling of over 1200 cycles under variable current rates. Facile one-step synthesis, fast charge storage kinetics, and attractive electrochemical performance establish polydiphenylamine as a notable organic cathode candidate for aqueous zinc batteries. • Polydiphenyl amine is introduced as a reversible high-voltage cathode for aqueous zinc batteries, operating by p-doping/de-doping redox of the amine center. • Ex situ solid-state NMR reveals the transformation of the pristine material into a cross-linked polymeric material during the first charge. • Pseudocapacitor-like charge mechanism and highly reversible redox chemistry result in high rate capability and stable battery cycling.