Synergistic interaction between amphiphilic ion additive groups for stable long-life zinc ion batteries

Abstract

The uneven deposition of zinc and hydrogen generation at the zinc anode interface constitute major impediments to the lifespan of aqueous zinc-ion batteries. Herein, an amphoteric ion additive, choline phosphate (CP), is proposed to stabilize the battery anode interface. The remarkable interplay between choline ions and phosphate groups assumes a pivotal role in homogenizing zinc ion deposition and regulating the behavior of free water molecules. Due to the negative electric field adsorption on the surface of the zinc anode, the positively charged choline ions will be adsorbed on its surface preferentially and prevent the approach of water molecules. The phosphate group interacts strongly with the zinc ion, permeating the solvated structure of these ions, regulating zinc ion flux, and immobilizing free water molecules through hydrogen bonding to impede unwanted side reactions. In summary, using CP additives yields a profound enhancement in enabling significantly extended cycle lifespans of both Zn//Zn symmetric batteries and LiFePO4 full batteries.