Engineering the First Coordination Shell of Single Zn Atoms via Molecular Design Strategy toward High-Performance Sodium-Ion Hybrid Capacitors

Atomically dispersed Zn moieties are efficient active sites for accelerating the electrode kinetics of carbons for sodium-ion hybrid capacitors (SIHCs), but the low utilization and symmetric configuration of Zn single-atom greatly hamper the Na ion storage capability. Herein, a molecular design strategy is employed to synthesize high-density Zn single atoms with asymmetric Zn-N3S coordination embedded in nitrogen/sulfur codoped carbon (Zn-N3S-NSC). The key to this strategy lies in the Zn power-catalyzed condensation of trithiocyanuric acid molecules to generate S-doped g-C3N4, which can in situ coordinate with Zn sources to form Zn-N3S moieties during pyrolysis. By virtue of the highly exposed Zn-N3S moieties, Zn-N3S-NSC presents ultrahigh reactivity, efficient electron transfer, and decreased ion diffusion barriers for SIHCs, rendering an impressive energy density of 215 Wh kg(-1) and a maximum power density of 15625 W kg(-1). Moreover, the pouch cell displays a high capacity of 279 mAh g(-1) after 4000 cycles. This work provides a new avenue for the regulation of the coordination configuration of single metal atoms in carbons toward high-performance electrochemical energy technologies at the molecular level.