Unveiling bulk-to-interface electrolyte regulation for ultralong-life Zn-ion batteries

Unsatisfactory Zn²⁺/Zn interfacial behavior together with parasitic side reactions on the Zn anode are key issues limiting the cycling stability of aqueous zinc-ion batteries (AZIBs). To address these issues, electrolyte additives have been extensively explored, yet their efficacies are often unsatisfactory due to unknown structure-performance relationships or diverse trade-off effects. Herein, a carboxybetaine oligomeric additive, OCBA, is demonstrated to exhibit comprehensive regulation, from the bulk electrolyte to the electrode interface. Through theoretical calculations and experimental investigations, we find that strong interactions between OCBA and water/Zn²⁺/Zn metal bring about the simultaneous promotion of ion migration either in the electrolyte or across the interface, elimination of Zn dendrite growth, deposition of Zn along the (002) facets, and suppression of hydrogen evolution and inactive byproducts. Remarkably, benefiting from this synergistic regulation, Zn//Zn cells achieve an ultralong lifespan of over 6660 h at 1 mA cm^-2 and 1 mAh cm^-2, while Zn//Cu cells deliver a high Coulombic efficiency of 99.7% for ≈3000 cycles. Furthermore, Zn//polyaniline full cells show excellent rate performance and cycling stability. This study reveals the working mechanism of electrolyte additives and provides an effective strategy for developing high-performance AZIBs by additive design.