Ion-dipole interactions regulated interface for stable high-depth of discharge Zn anode

Abstract

The instability of Zn metal anodes during deep cycling significantly hinders practical applications of aqueous Zn metal batteries in grid-scale energy storage. This work develops a citric acid aged Zn metal (CZ@Zn) with an ion–dipole interaction interface for stable Zn anodes under high depth of discharge (DOD). The CZ framework with large dipole moments and abundant electronegative functional groups facilitates rapid Zn2+ transport and the desolvation process through strong ion–dipole interactions, while simultaneously repelling negatively charged SO<inf>4</inf>2− anions and water molecules. This dual functionality effectively suppresses Zn dendrite growth and prevents surface passivation, thus achieving ultrastable Zn anodes under demanding deep cycling conditions. Consequently, symmetric CZ@Zn cells exhibit exceptional reversibility with an ultrahigh cumulative plating capacity of 9.25 Ah cm−2, a cycle life exceeding 200 h at a high DOD of 90 %, and a decent cycling lifespan at fluctuating DODs. The practical feasibility of CZ@Zn anodes is further validated in CZ@Zn//VO<inf>2</inf> full cells, achieving a high capacity retention of 81.3 % after 700 cycles.