Interface synergy strategy for efficiency and sustainable lithium extraction using LiMn2O4

Spinel LiMn 2 O 4 is promising for electrochemical lithium extraction from high-Mg 2+ /Li + brines, but Mn dissolution limits its cycling stability. Here, we propose an interfacial synergistic strategy: coating LiMn 2 O 4 with a carbon layer and incorporating sulfonated ionic polymers (Nafion) during electrode fabrication. The tortuous carbon pores, combined with Nafion's enrichment effect, increase the local Mn 2+ concentration near the interface. This accumulation suppresses the Mn 3+ disproportionation reaction in LiMn 2 O 4 crystals, thereby mitigating Mn dissolution. XPS and EPR analyses confirm the effective immobilization of Mn 2+ within the film electrode assembly. The modified film electrode assembly achieves a low Mn loss of 0.336% after 20 adsorption-desorption cycles. This work demonstrates that rational design and optimization of the critical interfacial layer in electrodes can substantially extend the cycling life of LiMn 2 O 4 film electrode assembly, providing a robust material foundation for practical applications.