Surface modification of spinel λ-MnO2 and its lithium adsorption properties from spent lithium ion batteries

Spinel λ-MnO2 ion-sieves are promising materials because of their high selectivity toward lithium ions, and this can be applied to the recovery of lithium from spent lithium ion batteries. However, manganese dissolution loss during the delithiation of LiMn2O4 causes a decrease in adsorption capacity and poor cycling stability for these ion-sieves. To improve the lithium adsorption properties of λ-MnO2 ion-sieves, surface modification with a CeO2 coating was studied using hydrothermal-heterogeneous nucleation. The structure, morphology and composition of the synthesized materials were determined by XRD, SEM, TEM and EDS. The effect of hydrothermal synthesis conditions and the amount of CeO2 coating on the adsorption performance of λ-MnO2 were also investigated. A 0.5 wt.% CeO2-coated ion-sieve was synthesized by heating at 120 °C for 3 h and it had better adsorption properties than the bare samples. The effect of ultrasonic treatment on the lithium extraction ratio from LiMn2O4 upon acid treatment at various temperatures was studied and the results were compared with conventional mechanical stirring. We found that ultrasonic treatment at lower temperature gave almost the same maximum lithium extraction ratio and was more efficient and economic.