Duodecuple H‐Bonded NH₄⁺ Storage in Multi‐Redox‐Site N‐Heterocyclic Cathode for Six‐Electron Zinc–Organic Batteries

Abstract

Designing multiple redox sites in electroactive organic cathodes that allow more electron transfer is a permanent target for energy storage. Here, six‐electron zinc–organic batteries are reported accessed by duodecuple H‐bonded NH4+ storage in N‐heterocyclic dipyrazino[2,3‐f:2′,3′‐h]quinoxaline‐2,3,6,7,10,11‐hexacarbonitrile (DQH) cathode. DQH features an extended π‐conjugated aromatic planarity enriched with super electron delocalization routes and dodecahedral‐active imine/cyano motifs, achieving a high capacity up to 385 mAh g−1 at 0.5 A g−1. Besides, DQH cathode redox‐exclusively couples with small‐hydration‐size and low‐desolvation‐energy‐barrier NH4+ ions (0.33 nm and 0.19 eV vs 0.86 nm and 0.36 eV of Zn2+) via flexible H‐bonding interactions. NH4+ topo‐coordination enables DQH anti‐dissolution in aqueous electrolytes to avoid common capacity decay of small organic molecules, and solves the instability and low interfacial reaction kinetics issues caused by rigidly and sluggishly repeated insertion of Zn2+ ions. This gives zinc–organic battery high‐rate ability (30 A g−1) and high lifespan (30 000 cycles at 10 A g−1).

Electrolyte Additive Strategies for Safe and High-Performance Aqueous Zinc-Ion Batteries: A Mini-Review

“…The cycling performance of ZIBs is determined by the transfer rate of Zn 2+ ions and the stable electrochemical reaction at electrode/electrolyte interfaces. − Due to the limitations of the parasitic reaction of the zinc metal anode and the dissolution of the cathode material, the capacity of ZIBs decreases rapidly. − Generally, ZIBs exhibit different working mechanisms in different electrolyte environments. In alkaline electrolytes, the (dis)­charge reactions mainly involve the insertion and extraction of H + ions. − In neutral/weakly acidic electrolytes, the (dis)­charge carriers are the coinsertion of Zn 2+ and H + ions. − Although ZIBs shown higher energy density in alkaline electrolytes, the excessive generation of ZnO and Zn­(OH) 4 ‑2 would reduce the reversibility of the Zn metal anode.…”