Rationalize the High Performance of Lithium Sorbents Derived from Gibbsite Guided by Phase Chemistry

Lithium aluminum layered double hydroxide chlorides (LADH-Cl) are the only industrial-level lithium sorbents. However, as an applied material, the composition-structure-property-performance relation is far from well constrained, leaving the manufacture and application of LADH-Cl lithium sorbents empirical rather than rational. Herein, we studied the phase evolution of gibbsite phase Al(OH)3 in concentrated LiOH aqueous solution, suggesting the formation of lithiated lithium aluminum layered double hydroxide (LADH-OH) with Al:Li molar ratio 2. However, LADH-OH is not an active ingredient as a lithium sorbent. The neutralization of LADH-OH with a dilute HCl aqueous solution resulted in the formation of the active LADH-Cl phase. Unlike the traditional LADH-Cl phase (g-LADH-Cl) generated from direct LiCl intercalation of gibbsite, LADH-OH derived LADH-Cl (b-LADH-Cl) has a topological parent of bayerite instead of gibbsite. This is one of the most important roots for different performances. Another source for the different performance is very likely from variations of the particle size and morphology when the raw gibbsite reacted with LiCl or LiOH aqueous solution. Nevertheless, we found that the limiting-delithiation of b-LADH-Cl is still the same as g-LADH-Cl, that is only maximum 1/3 lithium can be delithiated from the LADH-Cl phase without any decomposition into gibbsite or bayerite. This concluded that b-LADH-Cl and g-LADH-Cl have the same reversible lithium “sorption–desorption” capacity, even through different lithium affinity and sorption kinetics. Also, notably, the “sorption–desorption” performance of the optimal sorbent is very sensitive to the properties of service brines. These results substantially enlarged our knowledge of the LADH-Cl phase and provided a demo of the rational manufacture of lithium sorbent.