Evaluating lithium recovery using electrochemical membrane separation: cost analysis and design strategies

The increasing demand for Li-based chemicals necessitates advancements in sustainable recovery technologies. Ion-exchange membranes, such as Li superionic conductors, offer promising electrochemical solutions. However, the relationship between electrochemical fundamentals and techno-economic feasibility remains underexplored. This analysis presents a techno-economic evaluation of an integrated Li₂CO₃ production process, covering brine intake and pretreatment, direct electrochemical Li recovery, brine disposal, and LiCl conversion to battery-grade Li₂CO₃. We develop an optimization method that accounts for variations in brine composition (Li: 0.17–710 ppm) and Li-selective membrane prices ($500–$40 000 per m²) to establish stack design and operational guidelines to minimize energy and material consumption in producing 1 ton of Li₂CO₃ per day. We examine Li/Ca and Li/Mg selectivity, stack pressure drop limits, and operation at reduced recovery ratios. While a 20-bar pressure threshold is identified as optimal for cost savings, we highlight an alternative strategy – combining lower recovery ratios with adaptive electrochemical design – to further minimize costs without requiring higher pressure tolerance. While Li recovery from seawater remains costly, our findings indicate that for other brine sources, assuming a Li transference number of 1, production costs range from $2600 to $28 000 per ton of Li₂CO₃, with energy consumption varying from 5099 to 71 099 kWh, depending on Li concentration and membrane price. However, energy demand can increase by 170% to over 900% at lower binary selectivities of ∼22 to ∼5, primarily due to higher current density and voltage requirements. Our work provides guidelines on an efficient direct Li recovery from brines, paving the way to a more sustainable Li sourcing.