Selective recovery of lithium from spent LiFePO4 battery via a self-catalytic air oxidation method

To achieve the long-term healthy development of new energy vehicles and energy storage industries, the recycling of spent lithium-ion batteries is extremely significant. Air oxidation leaching at room temperature can achieve the efficient recovery of lithium from LFP scrap (generated in LiFePO4 material production), but this method is unsuitable for the treatment of cathode materials from spent LFP batteries. In this work, cyclic voltammetry measurements were first innovatively employed to clarify the reasons for the ineffective leaching of lithium from spent LFP materials via air oxidation leaching and provide the theoretical basis for intensified leaching. Subsequently, a novel method of self-catalytic air pressure leaching was proposed to selectively recover lithium from spent LFP batteries, which ingeniously employs green and cost-free air as the oxidant and self-owned Fe in the LiFePO4 as the O2 deliverer and catalyst. 98.9% Li and only 0.41% Fe, and 3.01% P were leached from spent LFP materials under 0.4 MPa of air pressure, n (H2SO4)/n (Li) ratio of 0.5, liquid to solid ratio of 20 mL/g, 90 °C, and 5 h. The leaching kinetic study was performed and it indicated that the leaching kinetics of Li was controlled by chemical reaction. By combining the results of the thermodynamic analysis and various characterization methods, the reaction course of this self-catalytic air pressure leaching was clarified. In particular, AC-TEM and SEM-EDS analysis showed that the dispersed carbon bands covered on the LiFePO4 particles have been destroyed during the oxidation leaching, which significantly promotes the lithium recovery rate. Finally, the economic feasibility and environmental impact evaluations demonstrated that the proposed method has the advantages of high recycling profits, environmental friendliness, and low carbon emissions.