From Limited to Tunable: Precise Protonation Engineering the Pore Structure of Kevlar Aramid Nanofiber Membranes for Lithium Batteries

Kevlar aramid (para-aramid) nanofiber (KANF) membranes hold great promise for applications in energy storage, separation, and biomedicine. However, this potential is limited by the difficulty in precisely controlling their pore structure, which results from strong inter-fiber interactions and the uncontrolled self-assembly of KANFs during processing. In this study, a precise protonation strategy is developed to control the self-assembly of KANFs, enabling the continuous production of KANF membranes with tunable pore structures. Through the targeted hydrolysis of ethyl acetate, which selectively supplies protons to deprotonated amide groups, the strong interactions between KANFs and solvents during phase inversion are effectively suppressed, thereby facilitating controlled KANF self-assembly. This controlled self-assembly approach yields membranes with broadly tunable porosity (56-87%) and pore sizes (20-800 nm), which can be achieved via atmospheric drying, making them suitable for a diverse range of applications. As a proof of concept, the KANF membranes with varying pore sizes are employed as separators and structural scaffolds in polymer electrolytes for lithium batteries, demonstrating excellent adaptability and electrochemical performance. These findings highlight the potential of tunable KANF membrane structures to meet the performance requirements across a wide range of advanced energy storage applications.