Dual-Pathway Proton Transport Blockade Enabling High Areal Loading Aqueous Zinc Metal Batteries

Abstract

Aqueous zinc-ion batteries are promising for grid-scale energy storage due to inherent safety and low cost. However, their practical application under high current densities is severely limited by the hydrogen evolution reaction (HER) at the zinc anode. Traditional interfacial modifications struggle to overcome the fundamental trade-off between suppressing proton transport and maintaining Zn 2+ conduction, often leading to rapid failure under high current densities. Herein, we propose a "Dual-Pathway Proton Transport Blockade" strategy via a molecularly engineered membrane. Composed of PVA blended with a minimal amount of zwitterion-grafted PPy, the membrane physically suppresses water-induced swelling and chemically disrupts hydrogen-bond networks, blocking the proton hopping pathway (Grotthuss mechanism). Concurrently, it restricts free water penetration, cutting off the hydrated proton path (Vehicle mechanism). Sulfonate groups serve as Zn 2+ -philic sites to enrich ions and facilitate desolvation, while quaternary ammonium groups repel protons. The membrane exhibits exceptional selectivity, reducing proton conductivity by over 100-fold versus Nafion while retaining a high Zn 2+ conductivity. Consequently, Zn||Zn cells achieve >2000 h cycling at 10 mA cm -2 /10 mAh cm -2 , and Zn||I₂ full cells reach 22,000 cycles. Notably, under practical conditions with high cathode loading (49.3 mg cm -2 ) or in pouch-cell configurations, capacity retention exceeds 96% after hundreds of cycles.