From waste to watt: Urban mining of phosphorus from sludge for LiFePO4 batteries

Phosphorus (P) is a critical element for global food security and advanced energy technologies. While traditionally recovered from sewage sludge for fertilizer, phosphorus is now gaining attention as a sustainable precursor for lithium iron phosphate (LiFePO 4 ), a leading cathode material for lithium-ion batteries. This short review highlights recent advances in recovering phosphorus from sewage sludge and its valorization for energy storage. Key recovery routes–such as thermochemical, hydrothermal, and acid-leaching processes–yield phosphate-rich compounds and sewage sludge ash (SSA) suitable for conversion into LiFePO 4 precursors. The review places particular emphasis on material purification, synthesis strategies, and the electrochemical performance of the resulting cathodes. We also critically examine persistent challenges, including impurity management, process scalability, and regulatory barriers, alongside the environmental and economic implications of displacing conventional phosphorus sources. By bridging wastewater management with advanced material synthesis, this work underscores the potential of “urban mining” to create a circular supply of phosphorus for sustainable battery technologies.