Harnessing eco-friendly additives to manipulate zinc-ion solvation structures towards stable zinc metal batteries

Abstract

Considerable research efforts have been dedicated to investigating the side reactions and the growth of Zn dendritic in aqueous zinc-ion batteries (AZIBs). The incorporation of organic solvents as additives in electrolytes has yielded highly promising results. Nevertheless, their pervasive use has been hindered by concerns regarding their toxicity, flammability, and economic viability. Herein, we propose the utilization of γ-valerolactone (γ-V), a novel eco-friendly solvent, as an alternative for conventional organic additives to improve the performance of Zn anode. Experimental investigations and theoretical analyses have verified that γ-V additives can diminish the Zn2+-desolvation energy and enhance Zn2+ transport kinetics. The adsorbed γ-V molecules modulate the nucleation and diffusion of Zn2+, facilitating Zn growth along the (002) crystal plane, thus inhibiting dendrite formation and side reactions. Consequently, the modified electrolyte with 3% γ-V exhibit highly reversible cycling for 2800 h at 1 mA cm−2 and 1 mA h cm−2 in Zn//Zn symmetric cell. The Zn//KVOH coin cells deliver a capacity retention of 74.7% after 1000 cycles at 5 A g−1. The Zn//KVOH pouch cells maintain a capacity retention of 78.7% over 90 cycles at 3 A g−1. Notably, the γ-V additives also effectively alleviate the self-discharge phenomenon. This work provides valuable insights on the development of aqueous zinc-ion batteries with superior safety through the modulation of electrolytes using eco-friendly additives.