Charge Gradient Separator Regulating Ion Transport towards Stabilizing Zn Metal Anode

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 SO₄^2- from approaching the Zn anode surface, thus effectively promoting the uniform Zn deposition and suppressing the side reaction. 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 under a practical depth of discharge of 42.7%. The practical Zn||NaV₃O₈·1.5H₂O full cell using 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.