One Stone, Two Birds: In-Situ Formed Single-Ion Conductor to Enhance Water Stability of Lithium Garnet and Uniformity of Lithium Deposition During Electrolytic Lithium Extraction

Abstract

With the rising demand for metal lithium, the electrochemical lithium extraction method utilizing solid oxide electrolytes has garnered significant attention. However, due to the inevitable Li+/H+ exchange between the solid electrolyte and water, the lithium extraction rate is constrained by the electrochemical performance of the solid electrolyte. Furthermore, for the potential direct application of the extracted lithium in lithium metal batteries, the uniformity of the extracted anode material is crucial. To this end, a surface modification method utilizing poly(acrylamide-2-methyl-1-propane-sulfonate) (PAMPS) and PAMPSLi is implemented on a typical solid electrolyte selective membrane, Li6.5La3Zr1.5Ta0.5O12 (LLZTO), and polypropylene separator. The in-situ formed PAMPSLi coating layer eliminates Li2CO3 from the surface of LLZTO, enhances water stability, and maintains a high ionic conductivity of 0.78 mS cm-1. The modified polypropylene separator enhances the uniformity of deposited lithium by increasing the lithium transference number to 0.66 and forming a stable solid electrolyte interphase (SEI). Consequently, the lithium extraction system can work stably under a current density of 0.10 mA cm-1 for 27 hours, and the products can be directly integrated into lithium batteries. This work presents a novel approach to the sustainable utilization of lithium resources and the development of high-performance lithium batteries.

Keywords: Garnet electrolyte, Lithium metal anode, single-ion conductor, electrolytic lithium extraction, salt-lake brine