| Jun 20, 2025 |
Precise ion sieving achieved with ultra-thin polymer membranesA new cross-linking method creates 3-micron membranes with angstrom-scale pores, boosting efficiency in flow batteries by overcoming selectivity-permeability trade-offs.(Nanowerk News) Polymeric membranes are widely used in separation technologies due to their low cost and easily scalable fabrication. However, unlike inorganic nanoporous materials such as metal-organic frameworks and covalent organic frameworks, which feature periodic and ordered channels, polymeric membranes produced through traditional methods—such as phase separation—typically have irregular and disordered pore structures. |
| This structural limitation makes it difficult to accurately separate ions or molecules of similar sizes, leading to a trade-off between selectivity and permeability. |
| In a recent study published in Nature Chemical Engineering ("Ultrathin membranes prepared through interfacial polymer cross-linking for selective and fast ion transport"), a research team led by Prof. LI Xianfeng from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) developed a novel interfacial polymer cross-linking strategy to fabricate ultra-thin polymeric membranes with nanoscale separation layers. |
| The fabricated 3-μm-thick polymeric membranes were applied in vanadium flow batteries, enabling operation at a high current density of 300 mA/cm2. |
 |
| Interfacial polymer cross-linking strategy enables ultra-thin polymeric membranes for fast and selective ion transport. (Image: DICP) |
| “We have developed a novel and simple strategy to reduce membrane thickness, which significantly lowers ion-transport resistance," said Prof. LI. |
| Using this strategy, the researchers constructed a nanoscale cross-linked separation layer on top of a polymeric supporting layer. The stable, covalently cross-linked structure enabled the overall membrane thickness to be reduced to just 3 μm. By varying the cross-linking time and types of agents, the researchers could tune the thickness and morphology of the separation layer. The cavities between the polymer chains ranged from 1.8 to 5.4 Å in size—forming a quasi-ordered reticular structure that allows for precise, angstrom-scale ion sieving. |
| This structure simultaneously achieves high ion selectivity and low resistance, effectively overcoming the traditional permeability and selectivity trade-off. The membrane’s high size-sieving capability and low-transport resistance resulted in a vanadium flow battery with an energy efficiency of 82.38% at 300 mA/cm2. |
| "Our study addressed long-standing challenges in polymeric membrane design and offers significant advances for both membrane-based separation and energy storage technologies," said Prof. LI. |
| Source: Chinese Academy of Sciences (Note: Content may be edited for style and length) |
