Spontaneous lithium extraction and enrichment from brine with net energy output driven by counter-ion gradients

To meet the increasing lithium demands created by global electrification, a fast, flexible, inexpensive and sustainable mining process is needed, which is yet to be realized. Here we explore an untapped energy source that is inherent in all ion-separation processes to achieve spontaneous Li extraction with net energy production. The driving force comes from the huge concentration difference of counter ions (usually chloride) between the feeding and receiving solutions. Experimental results under various feeding compositions can be well explained by the Gibbs–Donnan equilibrium. Utilizing a Li-selective ceramic membrane and a chloride-storing silver electrode, we successfully achieved Li extraction from simulated brine with an energy output of 1.6 Wh mol_Li⁻¹. The system is stable over 300 hours of operation, maintaining a high Li/Mg selectivity of 450. Moreover, even spontaneous enrichment can be achieved when the counter ion concentration is much greater than that of Li ion in the feeding brine. We anticipate that the concept of this work could not only reshape the Li supply chain but also seed a fundamental transformation of all ion-separation processes.