Biorefinery approach for lithium battery waste: Mechanochemical production of GQD membranes and advanced aquaculture wastewater treatment

The exponential growth of the global lithium-ion battery (LIB) market, driven by widespread adoption in consumer electronics, electric vehicles and renewable energy storage, has significantly escalated urgent environmental and resource management concerns associated with spent battery waste. Traditional recycling methods often involve hazardous chemical treatments and suffer from inefficient recovery of valuable materials, raising safety and ecological challenges. Consequently, the strategic reutilization of spent LIBs cathodes to recover valuable carbonaceous materials, particularly graphene derivatives, offers a compelling and environmentally friendly approach to resource conservation and waste minimization. Conventional graphene recovery techniques—including chemical, mechanical, thermal and electrochemical exfoliation—each exhibit inherent trade-offs between environmental impact, process complexity and retention of essential graphene properties. This has driven recent research toward sustainable green pathways, notably mechanochemical strategies that significantly reduce hazardous reagents and energy consumption. Among various graphene derivatives, Graphene Quantum Dots (GQDs) have garnered significant attention due to their distinctive quantum confinement effects, high surface area, abundant edge sites, tunable photoluminescence and outstanding electronic properties. These features make GQDs highly promising modifiers to enhance next-generation LIBs electrodes by improving electrical conductivity, lithium-ion storage capacity and charge/discharge rates. Despite ongoing challenges in scaling up high-quality, morphologically-controlled GQD synthesis, the integration of upcycled GQDs from spent LIBs presents a dual benefit: advancing electrochemical performance while supporting circular economy principles and sustainability goals. This comprehensive review summarizes recent advances in LIBs recycling, sustainable graphene recovery and GQD applications, emphasizing the critical nexus between green mechanochemical approaches and electrochemical enhancements and concludes with key challenges and future perspectives.