Towards Ultra-Stable Wide-Temperature Zinc-Ion Batteries by Using Ion-Sieving Organic Framework Membrane.

Aqueous zinc-ion batteries (AZIBs) offer notable advantages in safety and cost-efficiency, but Zn dendrite growth and unstable interfacial reactions hinder their commercial viability. A crucial factor in addressing these challenges lies in optimizing the separator to regulate ion transport and stabilize electrode interfaces. Herein, we propose a covalent organic framework (COF)-based separator with quasi-single-ion conduction, specifically a Zn-substituted sulfonate COF (COF-Zn) membrane, designed to tackle these issues. Featuring a high Zn transference number (0.87) and a thin 25 μm profile, the COF-Zn separator allows for reduced electrolyte usage (20 μL mg) while effectively minimizing cathode dissolution. Its quasi-single-ion conductivity and electronegative properties improve Zn anode's stability by lowering water activity. This separator enables ultra-stable AZIBs, as demonstrated in various full cells including Zn//4,5,9,10-pyrenetetrone (PTO), Zn//I and Zn//VO. Remarkably, the Zn//PTO cell achieves an energy density of 260 Wh kg, 100 % capacity retention under reduced electrolyte conditions, and stable all-weather cycling from -40 to +100 °C with a customized electrolyte.