Toward closed-loop hydrometallurgy: a critical review of wastewater reuse strategies for end-of-life LiFePO4 battery recycling

The rapid adoption of LiFePO₄ (LFP) batteries, driven by their safety and cost advantages, necessitates the development of sustainable recycling technologies tailored to their low-value composition. While hydrometallurgical methods enable efficient lithium recovery, they typically generate large volumes of wastewater, undermining both environmental and economic viability. This review critically examines recent advances in closed-loop hydrometallurgical recycling of end-of-life LFP batteries, with a particular focus on wastewater reuse strategies. A comprehensive classification of lixiviants, including inorganic acids, salt-based compounds, and alkaline and organic compound, is presented, highlighting wastewater reuse. Quantitative techno-economic simulations reveal that full wastewater reuse, starting from the second cycle, significantly reduces operational costs and enables positive net profit within four to five reuse cycles in regions with favorable energy and labor conditions. Despite these advancements, challenges such as impurity build-up, reagent stability, and limited long-term cycle testing remain. This review outlines current limitations and proposes future directions for scaling up closed-loop systems in alignment with the principles of green chemistry and circular hydrometallurgy.