Multi-TpyCo-based conductive supramolecular hydrogels constructed by "bridge bonds" for rechargeable Zn-air batteries with ultrastable cycling stability over 1100 h

For supramolecular hydrogels, a deep understanding of the gelation process and exploration of their application in rechargeable electrochemical batteries remain a significant challenge. Herein, this paper demonstrates a series of novel multi-TpyCo 2+ -based low-molecular-weight supramolecular hydrogelators and further discovers the spontaneous gelation mechanism by experimental and calculation results. The hydrogen bond and π-π conjugation have a synergistic driving effect in gelation. In particular, the hydrogen bond between the free Cl anion and H 2 O molecules serves as a "bridge bond" to connect nearby structural units, contributing to forming a stronger network structure. Owing to the difference of the spatial confinement effect of the gelator, gelled (Tpy) x Co x displays a conductivity-dependent activity for the oxygen evolution reaction, and (Tpy) 4 Co 4 presents the lowest overpotential of 264 and 301 mV at 10 and 100 mA cm −2 , respectively. More importantly, with (Tpy) 4 Co 4 as the air cathode, liquid rechargeable Zn-air batteries exhibit an ultrastable cycling stability of more than 1100 h (5500 cycles @2 mA cm −2 ) and a high energy efficiency of 65.3% with negligible performance decay. Moreover, the fabricated (Tpy) 4 Co 4 -based quasi-solid-state battery displays a superior stability of 270 h (1 mA cm −2 at 25 °C) and 25 h (0.5 mA cm −2 at −40 °C). The multi-TpyCo 2+ -based supramolecular hydrogel presents the remolding property and shows a low overpotential of 264 mV at 10 mA cm −2 for oxygen evolution reaction (OER) and an ultrastable cycling stability over 1100 h for liquid Zn-air battery.