Surface modification of spinel λ-MnO ₂ and its lithium adsorption properties from spent lithium ion batteries

Spinel λ-MnO ₂ 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 LiMn ₂ O ₄ causes a decrease in adsorption capacity and poor cycling stability for these ion-sieves. To improve the lithium adsorption properties of λ-MnO ₂ ion-sieves, surface modification with a CeO ₂ 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 CeO ₂ coating on the adsorption performance of λ-MnO ₂ were also investigated. A 0.5 wt.% CeO ₂ -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 LiMn ₂ O ₄ 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.