Conjugation Extended Redox Oligomer Integrated Freestanding Cathodes for High-Capacity Stable Zinc-Ion Batteries

Organic cathodes as promising alternatives for aqueous zinc-ion batteries (AZIBs) face challenges of limited capacity and low cycling stability. To address these concerns, a conjugation extended quinone oligomer, i.e., 2,2'-(9,10-dioxo-9,10-dihydrophenanthrene-2,7-diyl)bis(cyclohexa-2,5-diene-1,4-dione) (PB), is developed herein for integrating with the framework of 2D MXene nanosheets covalently bonded single-walled carbon nanotube (MXSC) as freestanding film cathodes for high-capacity stable AZIBs. The sufficient exposure of redox-active sites in hierarchical architecture enables synergistically enhanced conductivity, suppressed dissolution in electrolytes, and efficient ion/electron transfer for charge storage. The optimal PB@MXSC cathode contributes a highest specific capacity of 202 mAh g^-1 at 1 A g^-1 and 160 mAh g^-1 at 10 A g^-1, together with an exceptional 81.2% capacity retention after 12 000-cycle cycling at 10 A g^-1, rivaling the-state-of-the-art organic cathodes in the literature. Featuring three-fold higher tensile strength than pristine MXene, the cathodes are endowed with unparalleled mechanical durability and a retention of 87.6% capacity over 1 000 bending cycles. The experimental and theoretical analyses reveal the Zn²⁺ and H⁺ dual-ion co-storage mechanism. This work pioneers a universal design paradigm for high-performance flexible energy storage devices, bridging molecular engineering with advanced materials and sustainable electrochemistry.