Macromolecular Engineering of Poly(catechol) Cathodes towards High-Performance Aqueous Zinc-Polymer Batteries

Aqueous zinc-polymer batteries (AZPBs) comprising abundant Zn metal anode and redox-active polymer (RAP) cathodes can be a promising solution for accomplishing viable, safe and sustainable energy storage systems. Though a limited number of RAPs have been successfully applied as organic cathodes in AZPBs, their macromolecular engineering towards improving electrochemical performance is rarely considered. In this study, we systematically compare performance of AZPB comprising Zn metal anode and either poly(catechol) homopolymer (named P(4VC)) or poly(catechol) copolymer (named P(4VC₈₆-stat-SS₁₄)) as polymer cathodes. Sulfonate anionic pendants in copolymer not only rendered lower activation energy and higher rate constant, but also conferred lower charge-transfer resistance, as well as facilitated Zn²⁺ mobility and less diffusion-controlled current responses compared to its homopolymer analogue. Consequently, the Zn||P(4VC₈₆-stat-SS₁₄) full-cell exhibits enhanced gravimetric (180 versus 120 mAh g^-1 at 30 mg cm^-2) and areal capacity (5.4 versus 3.6 mAh cm^-2 at 30 mg cm^-2) values, as well as superior rate capability both at room temperature (149 versus 105 mAh g^-1 at 150 C) and at -35 °C (101 versus 35 mAh g^-1 at 30 C) compared to Zn||P(4VC)₁₀₀. This overall improved performance for Zn||P(4VC₈₆-stat-SS₁₄) is highly encouraging from the perspective applying macromolecular engineering strategies and paves the way for the design of advanced high-performance metal-organic batteries.