Prioritized recovery of lithium from spent lithium-ion batteries by synergistic roasting with Na2SO4: Precise regulation

[Display omitted] •Based on the synergistic effect between in-situ carbothermal reduction and Na2SO4 roasting, the synergistic roasting with black mass was proposed.•The mechanism for phase transformation of lithium during Na2SO4 synergistic roasting is elucidated.•This study focuses on green, low-carbon recycling of spent LIBs, addressing environmental and resource sustainability. Due to its dual attributes of environment and resources, the development of green and low-carbon and the recycling of valuable metals have become a research hotspot in the field of spent lithium-ion batteries recycling. For the black mass, the reductant of Na2SO4 was selected to achieve efficient and preferential extraction of lithium by regulating the formation of the reduction products, investigating the mechanism of the synergy between in-situ carbothermal reduction and Na2SO4 roasting. The results demonstrated that the leaching efficiency of lithium from Black Mass was 80.93% under the optimal conditions of 20 g Na2SO4 dosage, roasting temperature of 700 ℃, and roasting time of 150 min. Comprehensive characterization revealed that the addition of Na2SO4 facilitated the transformation of Li from Li2CO3 to LiNaSO4, which has high solubility, and preventing the excessive reduction of Ni/Co oxides to the metallic states. The efficient separation and enrichment of lithium from spent LIBs was achieved by the accurate targeted transformation of the NCM during the synergistic roasting process, promising applications in the spent lithium-ion battery recycling industry.