Direct Recycling of Lithium-Ion Batteries With Aqueous Relithiation: Mechanistic Insights and Recent Advances

This review explores the advances and challenges in direct recycling of lithium-ion battery (LiB) cathode materials via aqueous relithiation (AR), with emphasis on the thermodynamic and kinetic factors governing lithium migration and reintegration into degraded active materials across ternary layered oxides, olivine, and spinel crystal structures. While aqueous treatments, mainly hydrothermal relithiation (HR), demonstrate strong potential for restoring electrochemical performance, scalability remains a critical barrier. The advantages and limitations of batch studies in defining thermodynamic boundaries are evaluated, and pathways toward continuous processing, compositional upcycling to emerging chemistries, and standardized impurity reporting are proposed. The success of this method further relies on effective cathode sorting, advanced data-driven process controls, and the establishment of unified benchmarks to enable fair comparison across studies. Ultimately, aqueous relithiation lies at the intersection of scientific discovery and industrial application, where operational boundaries, logistical frameworks, and regulatory alignment will shape its transition into industry.