Unveiling the lithium deintercalation mechanisms in spent lithium-ion batteries via sulfation roasting.

[Display omitted] • Pyrite ore as the only additive is used for sulfation reaction of LiCoO 2. • The mechanism of the sulfation reaction of LiCoO 2 was obtained. • Lithium deintercalation has been verified through density functional theory calculations. • High purity Li 2 CO 3 could be produced from the lithium sulfate leaching solution. Recovery of valuable metals from spent lithium-ion batteries (LIBs) is of great importance for resource sustainability and environmental protection. This study introduced pyrite ore (FeS 2) as an alternative additive to achieve the selective recovery of Li 2 CO 3 from spent LiCoO 2 (LCO) batteries. The mechanism study revealed that the sulfation reaction followed two pathways. During the initial stage (550 °C–800 °C), the decomposition and oxidation of FeS 2 and the subsequent gas–solid reaction between the resulting SO 2 and layered LCO play crucial roles. The sulfation of lithium occurred prior to cobalt, resulting in the disruption of layered structure of LCO and the transformation into tetragonal spinel. In the second stage (over 800 °C), the dominated reactions were the decomposition of orthorhombic cobalt sulfate and its combination with rhombohedral Fe 2 O 3 to form CoFe 2 O 4. The deintercalation of Li from LCO by the substitution of Fe and conversion of Co(III)/Fe(II) into Co 3 O 4 /CoFe 2 O 4 were further confirmed by density functional theory (DFT) calculation results. This fundamental understanding of the sulfation reaction facilitated the future development of lithium extraction methods that utilized additives to substantially reduce energy consumption. [ABSTRACT FROM AUTHOR]