Semi-wet synthesis of high-performance Li1.6Mn1.6O4 for selective lithium extraction from Salt Lakes Brine

Abstract

Among the manganese-based lithium-ion sieves, Li1.6Mn1.6O4 has a high theoretical lithium adsorption capacity as a spinel ion sieve material. Small particle size orthogonal phase purity LiMnO2 powders were prepared by a semi-wet method and calcined in air at 400 °C to obtain Li1.6Mn1.6O4 a lithium-ion sieve precursor. The synergistic effects of oxygen atmosphere, heat treatment conditions and lithium/manganese molar ratio on the crystal structure of LiMnO2 and the lithium adsorption/desorption characteristics of Li1.6Mn1.6O4 were comprehensively investigated with XRD, SEM, TEM, XPS, Raman, DTA-TG and capacity retention study. Notably, when the initial lithium/manganese molar ratio was set at 1.1, and the sample underwent a calcination at 120 °C for 48 h under carefully controlled deoxygenation conditions, we observed the exclusive presence of the desired orthorhombic phase in the LiMnO2 sample. In contrast, when the synthesis conditions deviated from the optimized parameters led to the presence of the monoclinic phase of Li2MnO3. This highlights the sensitivity of Li1.6Mn1.6O4 properties to the synthesis conditions. The results of adsorption-desorption cycles show that the ion sieve Li1.6Mn1.6O4 prepared by heat treatment of ordered o-LiMnO2 is more stable, the structural stability of Li1.6Mn1.6O4 were characterized by high-temperature in-situ XRD experiments during heating from 30 to 800 °C. The equilibrium adsorption capacity was 34 mg g−1 in Qarhan Salt Lake brine at 10th cycle, and a remarkably low Mn dissolution loss rate of 0.6 %. The results have significant potential to advance the development of high-performance adsorbent in the Li-Mn-O system and contribute to the advances in lithium separation technology.