Hydrophobic low-polarity perfluorobutanesulfonate shielding enhances the performance of 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 that can adsorb onto Zn electrodes tend to form strong reactions with Zn²⁺, resulting in an increase in the desolvation energy barrier for Zn²⁺. Herein, potassium perfluorobutanesulfonate (FSK) is introduced as an additive to construct a hydrophobic, Zn-friendly and strongly electronegative network in an 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 density of 1 mA cm⁻², the assembled Zn‖Cu half-cell 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.