Charge gradient separator regulating ion transport towards stabilizing Zn metal anodes

Abstract

Aqueous Zn-ion batteries (AZBs) exhibit promising prospects for large-scale energy storage systems due to high safety and low cost. However, dendrite growth and parasitic side reactions caused by the uncontrolled ion diffusion at the Zn–electrolyte interface severely hinder the practical application of AZBs. Herein, we propose a charge gradient separator (CGS) using low-cost and environmentally friendly bacterial cellulose via a simple vacuum filtration method. The charge gradient structure within the separator can facilitate Zn²⁺ diffusion and simultaneously restrict SO₄²⁻ from approaching the Zn anode surface, thus effectively promoting uniform Zn deposition and suppressing side reactions. Consequently, the CGS enables the Zn anode to exhibit a prolonged cycling life of 800 h at a high current density of 10 mA cm⁻² and of 1100 h at a practical depth of discharge of 42.7%. The practical Zn‖NaV₃O₈·1.5H₂O full cell using the CGS delivers an initial areal discharge capacity of 3.8 mAh cm⁻² and operates stably over 800 cycles at 1 A g⁻¹, highlighting the potential of the CGS for high-performance AZBs.