Recycling lithium-ion batteries to regenerate graphite, silicon, and Si/C composite anodes: Review of advances between 2015 and 2025

The increasing deployment of lithium-ion batteries in electric vehicles, stationary energy systems, and consumer electronics has intensified the need for efficient recycling technologies to mitigate their environmental and economic impacts. Although recycling efforts have conventionally focused on cathode recovery, the growing adoption of silicon-enhanced anodes and the large mass fraction of graphite in modern cells underscore the importance of sustainable anode regeneration. This systematic review synthesizes findings from 132 high-quality studies published between 2015 and 2025 that investigate the mechanisms, challenges, and technological progress in recycling graphite, silicon, and Si/C composite anodes. The analysis indicates that mechanical, thermal, chemical, and electrochemical approaches each offer distinct advantages, whereas hybrid processes provide the most effective restoration of structural integrity and electrochemical performance. Silicon regeneration remains particularly challenging because of severe volume expansion and irreversible structural degradation, necessitating advanced strategies such as selective silicon oxide removal, carbon re-coating, and nanostructural reconstruction. Environmental and economic assessments consistently demonstrate that anode recycling can reduce energy consumption and CO₂ emissions by 50-80% compared with the production of virgin materials. Despite this progress, key challenges persist, including solid-electrolyte interphase removal, copper contamination, heterogeneous black mass composition, and limitations in selective separation. Future research opportunities lie in intelligent process optimization, green solvent systems, scalable hybrid recycling workflows, and improved recovery strategies for Si-rich anodes.