Reduction mechanism of bamboo powder pyrolysis in selective lithium extraction from spent lithium-ion batteries

In light of the increase in demand for lithium resources, selective recovery of lithium from spent lithium-ion batteries (LIBs) is becoming increasingly important. In the preferential lithium extraction process, the choice of reducing agent is crucial, which affects the efficiency of Li+ release. Here, a novel biomass reducing agent waste bamboo powder (BP) is proposed. The thermal reduction mechanism of BP on spent cathode powder (SCP) is explored in detail, and the effect of BP before and after carbonization on the lithium extraction effect is investigated. Based on the regulation of roasting parameters, the SCP can be reduced to Li2CO3, Ni, Co and MnO under the optimal conditions of 650 ℃ for 1.5 h with 1:1 mass ratio of BP/SCP. Furthermore, through thermodynamic calculations and physicochemical characterizations, it is found that the addition of gas-solid reaction in the BP reduction process is superior to the carbonized non-activated carbon (NC) and activated carbon (AC). Moreover, the large specific surface area of 1145.725 m2 g−1 for AC will lead to partial adsorption of lithium during the water leaching process. Finally, more than 99% of lithium is preferentially recovered from the reducing residue through a two-stage leaching process of water leaching and low concentration acid leaching. Water leaching process can recover 82.6% of lithium and the model of physical dissolution kinetics are constructed and systematically studied. This research achieves low-cost, green and selective recovery of lithium from spent LIBs, which has broad industrial application prospects.