Unlocking the potential of a multi-electron p-type polyheterocycle cathode: when it meets a small-size and high-charge anion

High-voltage p-type organic cathodes are attracting broad attention for boosting zinc batteries, but are hindered by single-electron reactions and low utilization of redox sites due to high reaction energy barriers with incompatible anions. Here we design polyheterocycle organics (PHOs) <i>via</i> grafting dual-site-active phenothiazine and piperazine motifs to form donor-acceptor-extended structures which show multi-electron p-type redox reactions for superior anion storage. With the decrease in anionic Stokes radius and the increase in charge density (TFSI^- → OTF^- → SO₄ ^2-), SO₄ ^2- exhibits the strongest bipedal ion-pairing ability with PHOs during oxidation <i>via</i> an ultralow activation energy (0.20 <i>vs.</i> 0.38 eV of OTF^- and 0.45 eV of TFSI^-). This facilitates fast and full utilization of phenothiazine/piperazine active motifs by small-sized and doubly charged SO₄ ^2- anions (99.5% <i>vs.</i> 83.2% of OTF^- and 58.1% of TFSI^-). Consequently, the PHO cathode delivers superior SO₄ ^2--storage energy density (317 Wh kg^-1) and cycling lifespan (71.4% capacity retention over 100 000 cycles), surpassing OTF^- (273 Wh kg^-1/67.1%) and TFSI^- storage (210 Wh kg^-1/60.2%), as well as reported p-type organics. This work presents a new paradigm for designing multi-electron organics compatible with optimized anions for better zinc batteries.