Room temperature and low-energy direct regeneration methods for spent cathode materials in lithium-ion batteries: Current advancements and future applications

Abstract: The growing deployment of lithium-ion batteries (LIBs) in electric vehicles and energy storage systems has intensified concerns over resource depletion, waste generation, and environmental impacts. Conventional recycling methods—pyrometallurgy and hydrometallurgy—recover valuable elements but are energy-intensive, chemical-heavy, and often yield downgraded products. Direct regeneration of spent cathodes has emerged as a low-energy alternative capable of restoring structural integrity and electrochemical performance without fully breaking down the material. This paper reviews recent advances in direct regeneration, with emphasis on emerging room-temperature pathways alongside established thermal and other non-thermal methods. Key factors affecting energy consumption, including pretreatment, lithium sources, reaction conditions, and reactor design, are critically analyzed. Regenerated cathodes produced through low-energy routes are compared with pristine materials, with evidence showing that room-temperature processes can recover crystal structure, cycling performance, and rate capability to near-virgin levels for selected chemistries. Techno-economic and environmental assessments further indicate substantial reductions in carbon emissions, operating costs, and dependence on critical raw materials. Remaining challenges include mixed cathode waste streams, degradation variability, and industrial-scale implementation. Future directions highlight the need for green chemistry, improved sorting technologies, and supportive policy frameworks to enable a scalable, circular LIB recycling ecosystem. Highlights: Room-temperature direct regeneration restored the structural integrity and electrochemical performance of spent cathode materials to levels comparable to pristine materials. These low-energy recycling strategies significantly decreased carbon emissions and operational costs relative to traditional thermal and chemical-heavy processes. Discussion: The actual attainment of a closed-loop "battery-to-battery" circular economy is debated due to the significant energy requirements and technical complexities involved in sorting increasingly heterogeneous cathode waste streams. Scientific tension exists regarding whether regeneration protocols labeled as "room-temperature" that still necessitate high-temperature annealing are fundamentally sustainable or low-energy alternatives. It remains an unsettled challenge whether room-temperature pathways can fully mitigate deep Li/Ni cation disorder and irreversible phase transitions in advanced high-nickel cathodes without the use of conventional thermal energy.