高効率・高安定な電気化学的直接リチウム抽出のためのチタン酸リチウムの活性化

Direct lithium extraction (DLE) from brine using electrosorption processes offers an environmentally sustainable alternative to evaporation-based mining, but its advancement has been hindered by the lack of electrode materials that combine high selectivity, fast kinetics, and long-term stability. Lithium titanate (LTO) is structurally robust and chemically selective yet remains electrochemically inactive under aqueous conditions. In contrast, manganese-based spinels exhibit strong redox activity but suffer from structural degradation. Here, we report a site-selective doping strategy that integrates the strengths of both material classes by incorporating Mn into the spinel framework of LTO. Crystallographic, spectroscopic, and electrochemical analyses reveal that Mn substitution of specific lattice sites modulates both Li⁺ transport pathways and redox-active centers, enabling enhanced intercalation kinetics and electronic conductivity without compromising the structural integrity of the crystal lattice. The optimized electrode material (H₁.₃₃Ti₁.₁₇Mn₀.₅O₄) achieves a record Li⁺ adsorption capacity of 43.58 mg/g at 350 ppm of Li⁺ with high selectivity and minimal capacity loss after repeated cycling with real salt lake brine. This approach transforms an electrochemically inert but stable spinel into a redox-active host, providing a generalizable pathway for designing acid-free and energy-efficient electrodes for sustainable lithium recovery from complex saline resources.