Electroactive quinone overlayer enables improved calendar-aging tolerance in zinc metal batteries

Aqueous zinc (Zn) metal batteries offer high volumetric capacity, low cost, and enhanced safety, but their calendar life is severely limited by unstable Zn–electrolyte interfaces, dendritic growth, and the progressive accumulation of electrically isolated dead Zn. Here, we report a thin, conformal, and electroactive anthraquinone (AQ) overlayer that couples redox activity with interfacial stabilization. By reducing lattice mismatch via Zn-inserted AQ intermediates (Zn–AQ), the overlayer directs preferential Zn(002) deposition, thereby minimizing dendritic formation and promoting uniform plating. Redox-active AQ species rejuvenate electrically isolated dead Zn through a spontaneous solid-state redox process, mitigating aging-induced Zn loss, a function not attainable with conventional interfacial strategies. In addition, the AQ overlayer promotes an inorganic-rich solid–electrolyte interphase that suppresses corrosion and hydrogen evolution. As a result, Zn full cells incorporating the AQ overlayer retain 94.2% of their initial capacity after 1000 cycles at 2 A g$^{−1}$ and maintain 79.6% Coulombic efficiency after 7 days of calendar aging. ... mehrNotably, Zn-free full cells (i.e., with a Zn-free anode) deliver 88.9% capacity retention after 100 cycles, in sharp contrast to only 20.6% for pristine Cu-based cell. These results establish electroactive organic overlayers as a promising route toward practical, improved calendar-aging stability of Zn metal batteries.