Unveiling nanopore-confined crystallization and coordination/de-coordination mechanisms of quinone molecules for ultrahigh-rate and ultralong-cyclability aqueous zinc–organic batteries

Abstract

Impregnating organic small molecules into porous carbon matrices is a prevailing strategy for aqueous zinc–organic batteries to address the problem of dissolution and conductivity of organic active materials for better performance. However, fundamental principles such as the nanopore-confined behavior of organic molecules and related electrochemical mechanisms are still unclear to date. Herein, we disclose that a “nanopore-confined metal–organic coordination chemistry” involving space-confined crystallization of quinone molecules and subsequent highly reversible Zn²⁺ coordination/de-coordination reactions with crystalline quinone molecule clusters within a porous carbon matrix enables superior performance for aqueous zinc–organic batteries, which is realized via a novel three-in-one strategy. The strategy integrating pore structure modulation, loading technique optimization and organic molecule selection can realize a high loading yet anti-dissolution of tetramethyl-benzoquinone (TMBQ) in a KOH activated MOF-derived carbon nanocage (KMCN), ensuring insolubility of organic active materials and fast Zn²⁺ diffusion kinetics. Consequently, the resultant TMBQ@KMCN cathode delivers a high reversible capacity of 315 mA h g⁻¹ at 0.5C, an unprecedented high rate capability of 155 mA h g⁻¹ at 150C (48.9 A g⁻¹), and an ultralong cycle life of 15 000 cycles at 20C with a capacity retention of 91.2%. This work provides important insights and guidance for designing high-performance organic electrode materials.