Green and Economic Lithium Recovery from Spent LiMn2O4 Batteries through Blue Vitriol-Driven Selective Sulfation Roasting

Abstract

Conventional lithium-ion battery recycling technologies suffer from poor economic performance, secondary pollution, and limited lithium selectivity, especially for low-value LiMn2O4 batteries. This study proposed an innovative blue vitriol-driven sulfation roasting-water leaching process for selective lithium extraction from spent LiMn2O4 batteries. Thermodynamic evaluations demonstrated the preferential conversion of lithium into water-soluble Li2SO4 while manganese and copper remain as insoluble oxides. Thermogravimetric analysis identified an optimal temperature range for efficient blue vitriol decomposition and selective lithium conversion. Under optimized conditions (700 °C, 0.7:1, 60 min), the sulfation roasting process exhibited 95.18% lithium recovery efficiency and 99.66% lithium selectivity while achieving near-zero SO2 emissions. Comprehensive characterization elucidated the transformation pathways from LiMn2O4 to Li2SO4, CuMn2O4, and Mn2O3. Density functional theory calculations revealed the preferential replacement of lithium in the LiMn2O4 by copper due to stronger Cu-O bonding and higher electron delocalization. The recovered Li2CO3 attained 99.59% purity, satisfying commercial battery-grade standards. Economic analysis revealed a net profit of $1,689.31 per metric ton of spent LiMn2O4 batteries, with additional revenue potential from byproducts (e.g. CuMn2O4 spinel). This research establishes an environmentally benign and economically viable approach for selective lithium extraction from low-value lithium-ion batteries, while providing a framework for broader battery recycling applications.