Degradation of components in lithium-ion batteries: from active-material failure pathways to degradation-aware diagnostics, regeneration, and circular management

This study presents a systematic, component-resolved, and lifecycle-aware review of degradation in lithium-ion batteries (LIBs), synthesizing evidence across active materials, electrolyte-mediated domains, supporting components, cross-cutting stress drivers, cell-to-pack heterogeneity, degradation-aware diagnostics, and end-of-life circular pathways. Using a structured multi-database protocol covering 2014–2025, 1260 records were identified, screened through explicit inclusion and exclusion criteria, and refined into 328 critical studies for comprehensive analysis. The synthesis indicates that lithium-ion battery degradation cannot be adequately explained by capacity fade alone because performance loss commonly reflects interacting pathways involving cathode structural instability, anode electro-chemo-mechanical damage, electrolyte decomposition, SEI/CEI reconstruction, lithium plating, separator and binder deterioration, current-collector degradation, impedance growth, gas evolution, swelling, internal-short susceptibility, and operating-condition asymmetry. A central contribution of the review is a seven-domain classification framework that connects local physicochemical degradation to pack-level performance loss, safety-relevant degradation states, diagnosable signatures, and circular-management implications. The evidence suggests that electrochemical ageing, cathode instability, electrolyte reactivity, and anode degradation remain dominant research clusters, while supporting components, standardized health descriptors, manufacturing-induced defects, bulk solid-electrolyte degradation, and degradation-informed regeneration remain comparatively underdeveloped. Recent advances in EIS, differential capacity analysis, gas analysis, thermal imageing, acoustic sensing, physics-informed models, and digital twins are shifting degradation assessment from post-mortem interpretation toward more actionable health intelligence. At end of life, degradation history appears to be an important route-selection variable because it can influence regeneration feasibility, direct-recycling suitability, safety screening, contamination management, and resource-recovery value. Overall, the review contributes toward an integrated degradation framework that links materials design, interface control, safety diagnosis, heterogeneity management, intelligent monitoring, and circular battery governance for safer, longer-lasting, and more sustainable lithium-ion battery systems.