Competitive adsorption of perfluorosulfonic ionomer restructuring the inner Helmholtz layer for stable Zn anodes

The water-dominated inner Helmholtz plane (IHP) is a significant contributor to undesirable hydrogen evolution reaction (HER) and dendrite formation, limiting the development of aqueous zinc-ion batteries (AZIBs). Here, we report a universal competitive adsorption approach to regulate the molecular composition and electrochemical behavior within the IHP by utilizing a small amount of perfluorosulfonic ionomer additive. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations reveal that the ionomer-dominated IHP can effectively expel water molecules due to stronger self-adsorption interactions facilitated by the ionomer additive on the surface of the zinc anode. Additionally, the solvation structure of Zn²⁺ has been modulated by the ionomer additive, also preventing the decomposition of water molecules during the desolvation process. Consequently, Zn//Zn symmetric cells achieve stable cycling for nearly 7 months at 1 mA cm⁻², even maintaining considerable reversibility at a higher current density of 100 mA cm⁻². The assembled NH₄V₄O₁₀//Zn full cells retain an impressive 92 % capacity retention after 600 cycles. This work of regulating the IHP through competitive adsorption of ionomer additives presents a promising avenue for the design of novel aqueous electrolytes.