Regulating lithium extraction based on intercalated SO42− in Li/Al-LDHs

Reasonable construction of Li/Al-LDHs with interlayer anions is essential to improve the adsorption performance, especially for intercalating SO42− anions and blocking Li+ desorption. Hence, anion exchange between Cl− and SO42− in the interlayer of Li/Al-LDHs was designed and prepared to demonstrate the strong exchangeability of SO42− for Cl− intercalated in the Li/Al-LDH interlayer. Intercalated SO42− enlarged the interlayer spacing and significantly transformed the stacking structure of Li/Al-LDHs, resulting in fluctuating adsorption performance with changes in the intercalated SO42− content at different ionic strengths. What is more, SO42− repelled the intercalation of other anions, thus inhibiting Li+ adsorption, as verified by the negative correlation between adsorption performance and intercalated SO42− content in high-ionic-concentration brines. Desorption experiments further revealed that enhanced electrostatic attraction between SO42− and the Li/Al-LDH laminates hindered Li+ desorption. Additional Li+ in the laminates was essential for preserving the structural stability of Li/Al-LDHs with higher SO42− contents. This work provides a new insight into the development of functional Li/Al-LDHs in ion adsorption and energy conversion applications.