Quaternized Poly(ether sulfone) Coupled LiMn1.9Cr0.1O4@Carbon Cloth for High-Performance Membrane Capacitive Li-Extraction

Abstract

Membrane capacitive deionization (MCDI) is a promising Li-extraction technology from salty brine to meet the growing demand for lithium sources. In this work, a Li⁺-selective quaternized poly(ether sulfone) coupled LiMn_1.9Cr_0.1O₄@carbon cloth (LMC@CC/QPES) is fabricated via a rapid UV-curing method and used as the flexible Li-extraction electrode in the MCDI system. The Li-extraction results for old brine from West Taijinar confirm that the optimal capacity can reach 28.57 mg·g^–1 with a retention rate of 82.36% after 200 cycles. This is ascribed to the stereoscopic carbon cloth as a current collector improving the active loading and charge transfer and the UV-curing polymer binder as a buffer layer repressing the initial manganese dissolution of spinel LiMn_1.9Cr_0.1O₄. Importantly, the LMC@CC/QPES electrode exhibits an enhanced Li⁺ selectivity (Li⁺/Mg²⁺ separation coefficient > 280) through ion sieving by the spinel lattice with electrostatic repulsion by the quaternized membrane. Considering the green preparation of the Li-extraction electrode, the assembled MCDI system using QPES assisting the LMC@CC electrode can provide considerable economic benefits for lithium recovery from old brine.