Pulsed Charging-Induced Interfacial Stabilization Enables Highly Stable Iron Phosphate Electrode for Ultrafast...

Amid the soaring global demand for lithium, electrochemical lithium extraction using iron phosphate (FePO₄) electrodes is promising, yet its practical application in salt lake brines is severely constrained by high Mg²⁺/Li⁺ ratios. Herein, we unravel the intrinsic degradation mechanism by demonstrating that Mg²⁺ intercalation weakens the Fe─O bonds in FePO₄, triggering Fe²⁺ dissolution, and inducing the formation of Fe₂O₃ surface species that deteriorate electrode performance. To tackle this critical challenge, we propose a novel pulsed charging protocol where reverse potentials not only efficiently flush out surface-intercalated Mg²⁺ but also enrich Cl^- on the electrode surface, thereby modulating the electronic structure and lowering the Mg²⁺ deintercalation barrier. The FePO₄||Ag cell integrated with this protocol exhibits superior Li⁺ extraction kinetics (∼20 mg g^-1 h^-1), high LiCl product purity (99.95%), and exceptional cycling stability (800 h operation with ∼80% performance retention) in real salt lake brines. This work establishes a theoretical basis for electrode protection and provides a robust strategy to advance high-efficiency electrochemical lithium extraction.