NaOH-assisted low-temperature roasting to recover spent LiFePO₄ batteries

Decreasing the operating temperature of pyrometallurgical methods for recycling spent lithium-ion batteries (LIBs) is key to reducing energy consumption and cost. Herein, a NaOH-assisted low-temperature roasting approach is proposed to recover spent LiFePO₄. During roasting, NaOH acts as an oxidizing agent to oxidize Fe (II) to Fe₃O₄ at 150°C, thus collapsing its stable olivine structure while PO₄^3- capturing Li⁺ and Na⁺ to form Li₂NaPO₄ and LiNa₅(PO₄)₂. The obtained Fe₃O₄ is then separated, and the resulting Li salt can be further recovered as Li₃PO₄ with a Li recovery efficiency of 96.7 % and a purity of 99.9 %. Economic and environmental analysis based on the EverBatt model shows that this low-temperature strategy reduces energy consumption and greenhouse gas (GHG) emissions, thus increasing the potential profit. Overall, NaOH-assisted low-temperature roasting is a prospective strategy that broadens the application of NaOH as an oxidant and opens up a new avenue for decreasing the temperature of recovering spent LiFePO₄ by pyrometallurgy.