MnOOH-seeded growth of uniform LiMn2O4 nanoparticles on CNT for high-performance electrochemically switched lithium extraction

Electrochemically switched ion exchange (ESIX) is a promising technology for lithium extraction from high Mg/Li ratio salt lake brines, yet conventional lithium manganese oxide composite electrodes suffer from loose interfacial binding and particle agglomeration. To address this issue, for the first time, we developed a precursor-hydrothermal lithiation strategy that integrates MnOOH crystal seed pre-anchoring and C-O-Mn interfacial chemical bonding to fabricate a uniform and stable carbon nanotube/lithium manganese oxide composite membrane electrode. In this strategy, MnOOH nanoparticles were pre-loaded onto carbonylated carbon nanotubes as crystal seeds and subsequently converted into spinel lithium manganese oxide, while the C-O-Mn interfacial chemical bonds were formed to anchor the lithium manganese oxide nanoparticles onto the carbon nanotube scaffold. The resulting composite membrane exhibited a low charge transfer resistance of 21.5 Ω and fast lithium ion diffusion kinetics (2.68 × 10 −12  cm 2 ·s −1 ). When tested in actual brine from the Qarhan Salt Lake, it achieved a lithium intercalation capacity of 20.21 mg·g −1 and a Li + /Mg 2+ separation factor of 116, while maintaining excellent cycling stability with a capacity retention rate of 93.07%, significantly outperforming the control samples prepared by conventional methods. Mechanistic analysis suggests that the C-O-Mn interfacial chemical bonds contribute to enhanced electron/ion transport, facilitate the stabilization of the interfacial structure, and help suppress the detachment of active materials, thereby substantially enhancing the electrode performance. This work provides an interfacial engineering strategy for high-performance ESIX electrodes.