Non-coordinating charge transfer enables ultrafast desolvation of hydrated zinc ions in the outer Helmholtz layer for stable aqueous Zn metal batteries

ABSTRACT The formation of a strong coordination structure, [Zn(H2O)6]2+ often increases direct contact between the solvated H2O and Zn anodes in the inner Helmholtz layer, which exacerbates undesirable side reactions and dendrite growth, hindering the practical application of aqueous Zn metal batteries. Here, we show that the solvated H2O can be effectively minimized by an artificial solid electrolyte interphase (SEI) consisting of highly nitrogen-doped amorphous carbon (NC) and perfluorosulfonic acid polymer (Nafion). Theoretical and experimental analyses reveal that NC raises the Fermi level of the composite SEI and activates the non-coordinating charge transfer from the SEI to [Zn(H2O)6]2+, which leads to ultrafast desolvation of hydrated Zn-ions in the outer Helmholtz layer; while the Nafion framework ensures selective transport channels for Zn ions. Remarkably, the derived NC-Nafion@Zn symmetric cell exhibits a long lifespan (3400 h, 1 mA cm–2; 2000 h, 5 mA cm–2); moreover, the NC-Nafion@Zn//Mn4O3-carbon nanotubes full battery delivers ultralong cycling stability of 9300 cycles at 2 A g–1 with a high retention of 91.3%.