A Photothermal Cotton-Thread-Based Crystallizer for Efficient and Selective Lithium Recovery from Brine

The rapidly growing demand for lithium (Li) necessitates the development of efficient and sustainable mining technologies. Evaporation ponds remain the dominant method for Li extraction from brines, but their low solar energy efficiency leads to a prolonged operation time and extensive land occupation. Here, we present a cotton-thread-based crystallizer that couples efficient interfacial solar evaporation with spatial ion separation for enhanced Li recovery. By optimization of both the crystallizer geometry and surface chemistry, the evaporation rate was boosted by ∼5.4 times compared to pure water, offering strong potential to shorten the operation time of traditional ponds. Among the tested surface modifications, the GO–PEI-modified crystallizer exhibited the highest Li/Na selectivity (up to 13.72), owing to its enhanced photothermal conversion, improved hydrophilicity, and zwitterionic microenvironment. A scaled-up system was further validated under outdoor conditions, demonstrating both practicability and scalability. This work offers an insight into surface-chemistry-guided ion selectivity and provides a promising approach for advancing solar-driven mining technology.