Review on sustainable strategies for lithium recovery from spent lithium-ion batteries

Lithium-ion batteries (LIBs) are essential to today's energy storage technology, powering from handheld devices to electric vehicles and grid-scale renewable energy installations. With demand for LIBs rising ever more strongly—fuelled by the global clean energy shift—the demand for sustainable lithium recovery has accelerated. Extraction of lithium using traditional mining is energy-wasting, environmentally disruptive, and not viable given dwindling natural reserves. Thus, recycling lithium from retired LIBs is critical not just for resource security but also for environmental minimization. Herein is an overview of existing technologies applied for lithium extraction from spent LIBs, with emphasis on four dominant methods: pyrometallurgy, hydrometallurgy, electrochemical extraction, and bioleaching. The technologies are compared based on commercialization stage, efficiency in lithium extraction, cost, environmental impact, and applicability. Although pyrometallurgy and hydrometallurgy are more conventional, they may require high energy expenditure and toxic chemical utilization. For comparison, new technologies such as bioleaching and electrochemical extraction provide less polluting and more selective processes but are yet to be developed for large-scale use. Newly developed innovations in deep eutectic solvent-aided leaching, mechanochemical treatment, and bio-electrochemical systems have exhibited potential in enhancing lithium extraction efficiency while reducing environmental footprint. In spite of advances in technology, < 1% of lithium is recycled world-wide, and there is an urgent need for optimizing and integrating the available technologies. This review paper contrasts these technologies and presents directions for the enhancement of lithium recycling techniques with the aims of realizing higher recovery rates, cost-effectiveness, and eco-friendliness. Eventually, designing effective recycling schemes will be important for underpinning a circular economy of lithium and in delivering long-term energy security.