Synthesis of zirconium-coated lithium ion sieve with enhanced cycle stability

Abstract

Lithium manganese oxide ion sieves (LMO-type) have excellent application prospects for extraction of lithium from brine due to their high adsorption capacities and superior selectivities. However, the dissolution loss of Mn affects their structural stability, and limits their industrial application. In this study, the zirconium-coated lithium ion sieve precursor LMZO was prepared by coating zirconium oxide into Li1.6Mn1.6O4 and performing solid-phase combustion. The results revealed that after acid leaching, the spinel structure and porous morphology of LMZO were maintained, which is beneficial for subsequent Li+ adsorption. The dissolution loss rate of Mn2+ decreased from 0.89 % to 0.349 % after coating, which was superior to that of pristine or coated Li1.6Mn1.6O4 materials previously reported. The lithium adsorption capacity of the zirconium-coated lithium ion sieve HMZO from Qinghai Kunty salt lake brine containing multiple coexisting ions was maintained at 25.96 mg/g at a Mg2+/Li+ concentration ratio of as high as 70, indicating that HMZO could be directly applied to highly saline brines. After 15 adsorption and desorption cycles, HMZO maintained a low dissolution loss of Mn and a large lithium adsorption capacity. This conclusion showed that HMZO has stable structure and excellent industrial application value. The Mn valence was higher in HMZO because the coating slowed the dissolution of Mn3+ and prevented dissolved Mn2+ from entering the solution; thus, the dissolution loss of Mn from HMZO was low. The adsorption of Li+ conformed to the pseudo-second-order kinetics model, indicating a Li+-H+ ion exchange mechanism.