Selective lithium uptake from seawater and lake brine is an important challenge in energy and environmental science. H1.6Mn1.6O4 with pseudospinel-type structure is a highly selective adsorbent for Li ions, but it is difficult to prepare large, highly crystalline H1.6Mn1.6O4 crystals with porous structure due to its thermodynamic metastability. Herein we demonstrate simple chemical processes that transform flux-grown, idiomorphic orthorhombic LiMnO2 (o-LiMnO2) cuboids of micrometer size into hierarchically structured H1.6Mn1.6O4 rods. We have optimized the flux growth conditions such as the Mn source, holding temperature, and solute concentration in order to yield large, single-phase o-LiMnO2 particles. The use of MnO under very low solute concentration (1 mol %) and high temperature (1000 °C) is critical to obtaining the single-phase, idiomorphic o-LiMnO2 cuboids. The metastability of o-LiMnO2 is confirmed by ab initio density functional theory calculation in comparison with other lithium manganates such as LiMn2O4 and Li2MnO3. The successive calcination and acid treatment allow the transformation of o-LiMnO2 into H1.6Mn1.6O4 rods with porous structure. The resultant H1.6Mn1.6O4 shows high Li+ adsorption capacity (∼5.6 mmol g-1), high Li+/Na+ selectivity, and good durability compared with existing H1.6Mn1.6O4 adsorbents.
All Science Journal Classification (ASJC) codes
- General Chemistry
- General Materials Science
- Condensed Matter Physics