Advanced biomimetic nanofiltration membranes for lithium recovery with anti-janus charge structure

Nanofiltration (NF) membranes with high Li⁺/X²⁺ (Co²⁺, Mn²⁺, etc.) selectivity are crucial for cost-effective Li⁺ recovery, addressing the global lithium shortage. However, conventional positively charged NF membranes typically exhibit Janus structure, conferring low Li⁺ penetration and permeability, and are negatively affected by the electrostatic shielding effects. Inspired by the internal electrical structure of dust storms, where positive-negative mosaic-like charge structure generates strong electric fields to facilitate particle transport, this study proposes a discrete micro-nano isolated island strategy to regulate the charge distribution within the NF membrane. A quaternary ammonium electrolyte was designed to modify the NF membrane, enabling the development of anti-Janus membranes with mosaic-like charge structure. The resulting anti-Janus membranes demonstrated an exceptional Li⁺/X²⁺ selectivity, exceeding that of conventional PIP-TMC membranes by 647%-904%, with Li⁺ penetration at 84.99% and permeability at 20.72 LMH/bar. Furthermore, this study introduces an evaluation metric, Critical Efficiency Product (CEP), for specifically assessing Li⁺ recovery performance.