Researchers in China report using air oxidation–water leaching to recover lithium selectively from spent LiFePO₄ (LFP) material, in which the high leaching efficiency of lithium and the good separation effect of lithium and iron were achieved simultaneously. An open-access paper on their work is published in the RSC journal Green Chemistry.

The use of LFP batteries in EVs is increasing rapidly, especially in China, due to low-cost, safety, excellent thermal stability and superior cycling performance. (Earlier post.) However, the researchers note, a huge number of end-of-life batteries will emerge due to the limited lifespan of LFP batteries (8–10 years). The toxic electrolytes, binder, and other organic chemicals will result in serious environmental pollution if the spent batteries are not properly treated.

The economics of current approaches to recycling of spent LFP batteries are challenging, the researchers noted, due to low lithium recovery rate, and high reagent and wastewater treatment costs.

To address these problems in the previous works during the selective lithium recovery from the spent LFP batteries, it is significant to develop an oxidant that is cheap, green, and efficient as well to replace the existing oxidants. As the most cheap and green oxidant, air may be suitable as the oxidant to selectively extract lithium from the LFP cathode material in the water leaching process. Besides, the reduction product of air is H₂O and will not introduce any impurities.

In this work, the kinetic process of air oxidation combined with water leaching was investigated, which could provide guidance for the increase of the reaction rate and leaching efficiency. Meanwhile, the parameters e.g., air flow rate, liquid-to-solid ratio, reaction temperature, time, and pH were systematically investigated. Characterization was subsequently adopted to clarify the leaching mechanism. Finally, economic viability was analyzed for the proposed recycling process of the LFP cathode material. The high leaching efficiency of lithium and the good separation effect of lithium and iron were achieved simultaneously via air oxidation–water leaching. With the merits of less reagent consumption, no secondary waste discharge and high economic profit, this work demonstrates a clean and efficient technology for the recycling of the spent LFP, conforming to the concept of green chemistry.

—Jin et al.