Tourmaline with an inherent electric field enhances electrochemical lithium extraction from low-quality brines

Selective and efficient lithium (Li) extraction from abundant untapped low-quality brines is crucial for meeting the surging global demand for Li. For addressing the challenges of extremely low Li⁺ concentration and poor Li⁺ mobility in low-quality brines, a bifunctional tourmaline-enhanced electrode system is developed. This system generates Li⁺ transport channels from the brines to spinel LiMn₂O₄ (LMO) electrodes for efficient Li extraction. The system achieved 99% pure Li₂CO₃ from a simulated West Taijinar Salt Lake brine (Mg/Li = 54.1). The Li⁺ mobility is accelerated by the inherent electric field of tourmaline and the enlarged unit-cell volume of LMO. The extraction capacity of 10%-tourmaline blended LMO (LMO-T_0.1) is 24.2 mg g⁻¹, 1.5 times higher than that of the LMO electrode. Notably, the negatively charged center of tourmaline is selectively recognized by Li⁺, enabling Li⁺ transport while binding Mg²⁺. Consequently, LMO-T_0.1 achieves a remarkable Li⁺/Mg²⁺ selectivity of 1570.7, significantly outperforming existing LMO-based electrochemical cells. Moreover, the universality of tourmaline is validated in a lithium iron phosphate electrode, highlighting its high potential as a scalable and cost-effective electrode additive for sustainable Li extraction from low-quality brines.