Preparation of Highly Stable Hydrophilic Electrodes Based on Thermally Crosslinked SPEEK and Their Application in Lithium Extraction from Salt Lake Brine by MCDI

The titanate coupling agent, through chemical bonding with hydroxyl groups on the HTO surface and good compatibility with the organic phase, improves the dispersion of the active material while enhancing interfacial bonding, effectively inhibiting electrode swelling. Heat treatment induces a thermal crosslinking reaction in SPEEK, enabling precise control over the electrode's crosslinking degree and hydrophilicity. Simultaneously, the sulfonic acid groups (-SO3H) in the SPEEK molecular chains provide additional adsorption sites for lithium ions.

This study systematically investigates the microstructure, hydrophilicity, and electrochemical performance of electrodes prepared with different binders, as well as their lithium extraction behavior in simulated salt lake brine. The results indicate that the SPEEK binder significantly improves electrode hydrophilicity, drastically reducing the water contact angle from 129° for PVDF-based electrodes to 40°. Electrochemical tests show that the specific capacitance of the optimized SPEEK-based electrode is 39% higher than that of the PVDF-based electrode.

In simulated salt lake brine systems, this electrode achieves a high equilibrium lithium adsorption capacity of 44.8 mg·g-1 and a Li/Mg separation factor α(Li/Mg) of 102.8. Remarkably, after 250 galvanostatic charge-discharge cycles, the adsorption capacity retention remains above 99%. The enhanced overall performance of the electrode is attributed to the synergistic effects of the hydrophilic interface constructed by SPEEK, the enhanced structural stability provided by the coupling agent, and the additional adsorption sites offered by the sulfonic acid groups.

This study provides a new strategy for binder design and interface engineering for high-performance MCDI lithium extraction electrodes.