Restraining Lattice Distortion of LiMn 2 O 4 Facilitates Fluidic Electrochemical Lithium Extraction from Seawater

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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 LiMn 2 O 4 using a simple wet chemistry coating method, introducing minimal structural defects in the LiMn 2 O 4 materials and enhancing stability with a LiNbO 3 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 .