Continuous Lithium-Ion Extraction via Fuel Cell Desalination

With the rising demand for lithium in various applications and the global shift towards sustainable technologies, there is increasing interest in eco-friendly and cost-effective extraction methods. Various direct lithium-ion extraction technologies are being applied or are in development; however, a significant need remains for more sustainable systems and materials that minimize the use of additional chemicals and simplify the process.¹ Ceramic membranes have garnered significant interest due to their high ionic conductivity, excellent chemical compatibility with various materials, high electronic resistance, and good thermal stability.² This study introduces a continuous lithium-ion extraction method utilizing a multi-channel fuel cell desalination system with the lithium selective-ceramic membrane powered by oxygen and hydrogen gases as energy carriers. As feedwater and gases are supplied to the system, Li⁺ ions migrate into the catholyte channel through a lithium-selective membrane, contributing to the formation of dissolved LiOH. Concurrently, Cl^- ions pass through the anion exchange membrane into the anolyte channel, where they combine with H⁺ ions to produce aqueous HCl.³ To enable lithium-ion selectivity, We incorporated a lithium superionic conductor ceramic membrane into the fuel cell desalination system. The ceramic membrane, Li_1+<i>x</i>Al<i>_x</i>Ge_2–<i>x</i>(PO₄)₃(<i>x</i>=0.5, LAGP), enabled the selective separation of Li⁺ ions toward the other cations from the lithium-ion-containing feedwater. The concentration of all cations was determined using an inductively coupled plasma optical emission spectrometer (ICP-OES), and selectivity factors were investigated in two feed waters: seawater and mine water. The selectivity factors between Li⁺ and Na⁺ ions were found to be K_Ptc-seawater(10.2), K_{Ptc-minewater}(3.8), K_{TiO2/Ptc-seawater}(20.5), and K_{TiO2/Ptc-minewater}(6.0), respectively. We also coated titania-deposited platinum electrodes with atomic layer deposition to enhance the system's stability and durability. Transmission electron microscopy confirmed that the titania layer was uniformly coated on the electrode surface. Performance tests on the fuel cells using mine water and seawater demonstrated that the titania coating significantly improved selectivity and purity. When using the PtC catalyst with a purity level of 75% in seawater, the lithium-ion extraction rate achieved was 0.017 mg/cm²/h. With the TiO₂/PtC catalyst, the extraction rate was 0.011 mg/cm²/h, achieving a purity level of 95%. Additionally, the process generated 0.6 Wh of electricity per gram of lithium extracted.<br/><br/><b>References:</b><br/><br/>1. A. Z. Haddad, L. Hackl, B. Akuzum, G. Pohlman, J. F. Magnan and R. Kostecki, <i>Nature</i>, 2023, <b>616</b>, 245-248.<br/>2. A. Manthiram, X. Yu and S. Wang, <i>Nature Reviews Materials</i>, 2017, <b>2</b>, 16103.<br/>3. C. Kök, L. Wang, J. G. A. Ruthes, A. Quade, M. E. Suss and V. Presser, <i>ENERGY & ENVIRONMENTAL MATERIALS</i>, 2024, <b>n/a</b>, e12742.