Correlative insights into the degradation pathways and direct regeneration healing mechanisms of spent lithium-ion battery active materials

Repurposing spent Lithium-ion batteries (LIBs) is a sustainable and economical approach to meet the growing demand for LIBs as their usage continues to expand in a plethora of applications. Recycling/reusing the LIBs that comprise critical raw materials like Li, Ni, Co, graphite, etc., accounting for ∼50 % of the total LIB cost, offers significant economic and environmental benefits within a sustainable circular ecosystem. Direct regeneration of electroactive materials proves to be a more efficient and sustainable alternative to traditional methods, as it focuses on restoring the lost performance of electroactive materials through simple rejuvenation processes. In contrast, conventional routes involve metal extraction and the synthesis of new materials. This article explores the macro and microstructural changes occurring in LIB anodes and cathodes from virgin to retirement and subsequent regeneration. Various direct regeneration methods are summarized, highlighting the structural transformations and healing mechanisms of graphite anodes, layered, spinel, and olivine cathodes. Further, bottlenecks of technological readiness of direct regeneration were addressed with viable solutions. • Structural, interfacial, and stoichiometric degradation routes are summarized. • Direct regeneration healing mechanisms were emphasized. • Disparities among pristine, degraded, and regenerated materials were evaluated.