A review on echelon utilization and cathode material recycling of retired power batteries: Recovery efficiency and carbon emission reduction benefits

The rapid proliferation of electric vehicles has created an urgent need to manage the surging volume of retired lithium-ion batteries (LIBs), driven by both resource scarcity and environmental concerns. Following PRISMA guidelines, this review synthesizes 251 studies to evaluate end-of-life strategies for LIBs, specifically echelon utilization and recycling technologies like pyrometallurgy, hydrometallurgy, and direct regeneration. Each recycling route presents distinct trade-offs. Echelon utilization extends battery life and reduces carbon emissions by repurposing them, but inconsistent degradation limits the lifespan of recombined systems. Hydrometallurgy offers high recovery rates and precise metal separation, yet it generates significant carbon emissions from chemical reagents and wastewater treatment. Pyrometallurgy is mature and suitable for large-scale recycling but suffers from poor metal selectivity and extremely high energy consumption. Direct regeneration provides superior carbon emission reduction benefits and conserves resources, but it remains confined to the laboratory and is not yet commercially viable. This review conducts a comparative analysis from the dual perspectives of recycling efficiency and carbon emission reduction benefits, evaluates the benefit differences among the four major technical pathways, and fills the gap of insufficient comprehensive comparison in previous similar studies. Finally, it analyzes the core challenges and future directions, providing theoretical and practical guidance for improving lithium battery recycling efficiency and promoting the development of a circular economy for metal resources.