Biomimetic separator with synergistic ion and solvent transport regulation for practical and high-stability zinc metal batteries

Abstract

Aqueous zinc metal batteries (AZMBs) are hindered by dendrite growth, cathode structural deterioration and side reactions, which arise from uneven diffusion of Zn²⁺ with sluggish de-solvation kinetics and H₂O accumulation at the electrode interfaces. These challenges are closely related to electrolyte solvent and ion transport behavior, which are expected to be resolved through meticulous separator design. In nature, the enzyme-gated ion channels in biological cell membranes facilitate selective ion transport with rapid desolvation, through their specific pore size and enzymatic gating mechanisms. Herein, inspired by intricate structure-function relationship of the enzyme-gated ion channels, we propose a lightweight and mechanically stable separator composed of bacterial cellulose and vermiculite. This separator demonstrates a synergistic effect that enhances selective transport and desolvation kinetics of Zn²⁺ while trapping active H₂O in its bulk phase. This promotes uniform Zn²⁺ diffusion and creates a stable, H₂O-deficient electrolyte environment at electrode interfaces. Such separator enables Zn anodes to achieve a lifespan exceeding 7000 hours (3500 cycles) with a high average Coulombic efficiency of 99.77 %, and allows the Mn_0.5V₆O₁₃ cathode (4 mAh cm⁻²) with excellent self-discharge resistance and superior cycling performance with 89.4 % capacity retention over 500 cycles at 0.3 A g⁻¹. Notably, full cell using this separator exhibits remarkable cycling stability for over 400 cycles at a low N/P ratio of 4.4. This innovative separator not only signifies substantial advancements toward practical application of AZMBs, but more importantly, its design concept inspired by nature, from biomimicry to beyond biomimicry, provides valuable insights for future material development.