Pilot-scale recovery of high-purity Li2CO3 and FePO4 from real wastewater for sustainable full synthesis of LiFePO4 battery.

Iron phosphate (FePO4) and lithium carbonate (Li2CO3) were valuable raw materials for producing of LiFePO4 batteries used in electric vehicles. Significant amount of Li+ and PO43- were wasted in wastewater that could be recovered as potential resources treasury. Here, we reported a sustainable full synthesis method of LiFePO4 battery, based on the pilot-scale recovery of high-purity Li2CO3 and FePO4 from oil-gas field wastewater and biogas slurry. Specifically, a high Li2CO3 recovery efficiency of 95.5 ± 0.71% was achieved from oil-gas field wastewater using an inorganic-organic Li2TiO3 composite (IOC) adsorbent. Then, high-purity Li2CO3 (Li2CO3-HP) of 99.20% was successfully synthesized from the Li+-rich solution. Meanwhile, Fe-sludge recovered from advanced treatment unit of wastewater treatment plant (WWTP) was reused as a P-adsorbent to enrich PO43- from biogas slurry, yielding P-rich sludge. Thus, PO43- in Fe-sludge and biogas slurry could be simultaneously recovered for the synthesis of 97.76% high-purity FePO4 (FePO4-HP) with a recovery rate of 92.6 ± 0.6% by Fe3+ supplement and pH adjustment. Notably, the LiFePO4 battery fabricated by the recovered Li2CO3-HP and FePO4-HP exhibited an excellent discharge capacity of 68.9-90.9 mAh g-1 at a 0.5 C. This study provided a novel approach for the green production of high-purity raw Li-battery materials, offering an innovative solution for the full synthesis of LiFePO4 batteries.