Hygroscopicity-driven spontaneous sustainable direct lithium extraction.

Current lithium extraction processes demand high inputs of energy, chemicals, and freshwater because they rely on non-spontaneous separation steps. To address these limitations, we introduce a spontaneous, hygroscopicity-driven direct lithium extraction method that leverages the unique entropy-increasing deliquescent behavior of lithium chloride hydrate (LHT) to extract and enrich lithium from solid deposits such as brine mining slags. At controlled relative humidities (12-30% RH), crystalline LHT selectively adsorbs water moisture to form a lithium-enriched concentrate, while co-occurring salts (halite, sylvite, bischofite, gypsum) remain in the solid phase. This phase-selective deliquescence enables rapid solid-liquid separation without external water, reagents, or heating. By optimizing humidity and moisture flux, we achieve swift lithium recovery of up to 96% with concentrations reaching 97,000 ppm, far exceeding industrial grade requirements. We further validate the method's robustness across binary and multicomponent mixtures, as well as actual slag samples under mining conditions. The results demonstrate competitive performances over a wide range of feeding ratios and seasonal changes, and the extraction times only take minutes to hours as compared to months. This entropy-increasing, ambient-temperature modular process minimizes energy, chemical, and water use, and it offers broad resource tolerance for lithium extraction and mining waste valorization.