Hydrophobic Low-Polarity Perfluorobutanesulfonate Shield Enables Dendrite-Free Aqueous Zn-Ion Batteries

Abstract

Unavoidable side reactions and Zn dendrite growth have long constrained the practical application of aqueous Zn-ion (Zn2+) batteries. Electrolyte additive engineering is a typical strategy for battery modification. However, highly polar additive molecules which can adsorb onto Zn electrode tend to form strong reactions with Zn2+, resulting in increasing the desolvation energy barrier for Zn2+. Herein, potassium perfluorobutanesulfonate (FSK) is used to construct a hydrophobic, Zn-friendly and strongly electronegative network in electric double layer (EDL) on the Zn surface, which can homogenize Zn2+ flux and suppress side reactions, markedly extending cell lifetime. Meantime, the uniformly distributed and electron-withdrawing groups remain excluded from the primary solvation sheath, avoiding any penalty on desolvation kinetics. Such EDL regulation enables symmetric cells with FSK to cycle steadily for 1500 h at 1 mA cm-2 and 1 mAh cm-2 and delivers a high capacity retention in Zn||V2O5 full cells over 1000 cycles. At a current of 1 mA cm-2, the Zn||Cu half cell assembled operates for 1400 cycles (2800 h) with an average Coulombic efficiency (CE) of 99.75%. This demonstrates that FSK markedly improves cell durability by homogenizing the Zn2+ flux, enabling smoother deposition and suppressing side-product formation. This work offers a new perspective on tailoring solvation structures and the EDL through ionic additives.