Restraining Lattice Distortion of LiMn₂O₄ Facilitates Fluidic Electrochemical Lithium Extraction from Seawater

Reversible electrochemical extraction using cathode materials shows great potential for selective lithium extraction from low-concentration aqueous sources. However, ion selectivity and structural distortion challenges have limited its application to sources like seawater. Here, we synthesize Nb-modified LiMn₂O₄ using a simple wet chemistry coating method, introducing minimal structural defects in the LiMn₂O₄ materials and enhancing stability with a LiNbO₃ coating to limit lattice expansion. Additionally, operando XRD reveals reduced lattice distortion during Li⁺ intercalation/deintercalation. Electrochemical tests show that the composite achieves high stability (over 100 cycles), fast Li⁺ electrosorption, and robust ion selectivity. Furthermore, utilizing a fluidic electrochemical approach, we extract lithium from simulated seawater (3.5 ppm of Li⁺), achieving an absorption capacity of 13.8 mg g^-1 and an energy consumption of 9.96 Wh g^-1.