Application of Carbon Nanotubes Coated with Hydrazone-Bond-Linked Polymer in Aqueous Zinc-Ion Batteries

Abstract

The development of aqueous zinc-ion battery (AZIB) cathode materials with low solubility, high specific capacity, and long cycle life is of critical importance. Organic polymers have drawn considerable research interest largely because they contain abundant redox sites and show low solubility in electrolytes. In this study, poly(2-(2-((1Z,4Z)–2,5-dihydroxy-4-(methylimino)cyclohexa-2,5-dien-1-ylidene)hydrazineyl)-N-methyl-2-oxoacetamide) (PDHN) was successfully synthesized via a condensation reaction and in situ grown on carbon nanotubes (CNTs) (10 wt %) to form a PDHN@CNT composite. PDHN possesses multiple redox sites and a high theoretical capacity while the introduction of CNTs enhances the utilization of redox centers, increases the specific surface area, and enables rapid reaction kinetics. At 0.1 A g–1, PDHN@CNT delivers 433 mAh g–1 as its reversible specific capacity. After 10,000 cycles at 10 A g–1, 86% of that capacity is retained. This study shows that incorporating CNTs into polymers having multiple redox sites to form composites works as an effective strategy to achieve AZIBs with high specific capacity and long cycle life.