A High-Voltage n-type Organic Cathode Materials Enabled by Tetraalkylammonium Complexing Agents for Aqueous Zinc-Ion Batteries.

Tetrabutylammonium (TBA) salt of hexacyano-substituted cyclopropane dianion (Cp(CN) ) is prepared through a facile two-step synthetic protocol from commercially available materials and fully characterized as a high-voltage n-type organic cathode in rechargeable aqueous zinc-ion batteries (AZIBs). The addition of tetrabutylammonium triflate (TBAOTf) to the electrolyte mitigates dissolution issues, leading to enhanced cycling stability. Remarkably, the Cp(CN) cathode demonstrates a high discharge voltage of 1.43 V in AZIBs and retains 85% of its capacity after 1000 cycles at a high loading of 10 mg cm and a cycling rate of 10C. These results, combined with spectroscopic analyses, elucidate a reversible two-electron redox process of Cp(CN) facilitated by the insertion/de-insertion of TBA cation. These findings underscore the potential of Cp(CN) as a conversion-based n-type cathode in energy storage applications.