Role of stacking faults and hydroxyl groups on the lithium adsorption/desorption properties of layered H2TiO3

Layered H2TiO3 ion sieve materials have shown promising selective lithium adsorption properties from brine solutions. Chemical delithiation of Li2TiO3 results in an increase of stacking faults and formation of isolated and hydrogen bonded OH groups. There is a critical knowledge gap in understanding the role of these stacking faults in lithium adsorption/desorption kinetics. Moreover, there is a lack of understanding in manipulation of surface hydroxyl groups to improve the lithium adsorption properties. In this work, layered Li2TiO3 (LTO) was synthesized using two different techniques, i.e., solid-state (ss-LTO) and hydrothermal (HT-LTO) methods to introduce varying concentrations of stacking faults. It was observed that HT-LTO synthesis method has a higher concentration of stacking faults, which results in slower elution of lithium from the precursor compared to ss-LTO. Interestingly, after complete lithium elution, both ss-H2TiO3 and HT-H2TiO3 ion sieves showed similar lithium adsorption properties. We also show that the lithium adsorption properties of layered H2TiO3 can be increased by oxygen annealing of the Li2TiO3 ion sieve precursor. Oxygen annealing improved the maximum lithium adsorption capacity by over 7% in a buffered solution (pH = 9.50) due to the increase in the relative amount of lattice oxygen and isolated surface hydroxyl groups. Spectroscopic studies (XPS, FTIR, and Raman) were used to further investigate and corroborate role of stacking faults and surface hydroxyl groups in the lithium adsorption/desorption process.