High-voltage multi-S-heterocyclic covalent organic frameworks for zinc–organic batteries with high energy density and ultralong life

Abstract

Organic p-type cathodes for Zn–organic batteries (ZOBs) have high voltage (1.0–1.2 V), but exhibit limited redox capacity (generally <250 mAh g⁻¹) due to low-density active sites. Here, we design multi-S-heterocyclic covalent organic frameworks (S-COFs) by integrating two-electron dithiophene and three-electron trithiophene motifs via a condensation reaction, which act as a new p-type cathode for high-performance ZOBs. Electron-rich S-heterocyclic motifs contribute to ultralow-activation-energy electron delocalization paths (0.25 eV) and low molecular orbital energy levels (2.26 eV), thus giving a high redox voltage of 1.3 V for Zn‖S-COF batteries. Furthermore, a stable 30 e⁻ charge storage is accomplished in dithiophene/trithiophene modules of the S-COF cathode by (de)coordination with CF₃SO₃⁻ anions, affording a high capacity of 310 mAh g⁻¹. This remarkable combination of high voltage and capacity propels the energy density of ZOBs to a high level (403 Wh kg⁻¹). Besides, the excellent anti-dissolution ability of the S-COF cathode in aqueous electrolytes extends the battery life to 60 000 cycles with 81.2% capacity retention at 10 A g⁻¹. Our work establishes a new paradigm to design high-voltage-capacity COFs, paving the way for next-generation high-performance ZOBs.