Design of Photothermal "Ion Pumps" for Achieving Energy-Efficient, Augmented, and Durable Lithium Extraction from Seawater.

Extracting lithium from seawater has emerged as a disruptive platform to resolve the issue of an ever-growing lithium shortage. However, achieving highly efficient and durable lithium extraction from seawater in an energy-efficient manner is challenging, as imposed by the low concentration of lithium ions (Li) and high concentration of interfering ions in seawater. Here, we report a facile and universal strategy to develop photothermal "ion pumps" (PIPs) that allow achieving energy-efficient, augmented, and durable lithium extraction from seawater under sunlight. The key design of PIPs lies in the function fusion and spatial configuration manipulation of a hydrophilic Li-trapping nanofibrous core and a hydrophobic photothermal shell for governing gravity-driven water flow and solar-driven water evaporation. Such a synergetic effect allows PIPs to achieve spontaneous, continuous, and augmented Li replenishment-diffusion-enrichment, as well as circumvent the impact of concentration polarization and scaling of interfering ions. We demonstrate that our PIPs exhibit dramatic enhancement in Li trapping rate and outstanding Li separation factor yet have ultralow energy consumption. Moreover, our PIPs deliver ultrastable Li trapping performance without scaling even under high-concentration interfering ions for 140 h operation, as opposed to the significant decrease of nearly 55.6% in conventional photothermal configuration. The design concept and material toolkit developed in this work can also find applications in extracting high-value-added resources from seawater and beyond.