Upgrading polycrystalline battery cathodes to single-crystal NMC622 via morphology-controlled recycling

Summary: The importance of recycling lithium-ion batteries is growing within the battery supply chain as a promising answer to economic and environmental challenges. Many initiatives are in progress to improve battery recycling technologies, as existing methods encounter major obstacles. Here, we report a polyol-metallurgical recycling process to upgrade polycrystalline cathodes to single-crystal cathodes, while detailing the coprecipitation and cathode resynthesis steps. Using citric acid and ethylene glycol enables effective leaching, simple separation, and controlled coprecipitation. Leveraging the distinct poly-esterification reactions in the precipitation phase, we achieve precise control over morphology and particle sizes. Using the coprecipitates, we have successfully resynthesized a LiNi0.6Co0.2Mn0.2O2 cathode with a similar elemental composition compared to the pristine cathode, free of impurities, and exhibiting a single-crystal morphology featuring grain sizes in the range of 10 μm. The study showcases the potential of polyol metallurgy as a novel and efficient method for recycling lithium-ion batteries and synthesizing advanced cathode materials. Science for society: Lithium-ion batteries power electric vehicles, portable devices, and renewable energy storage, however, their production and disposal create significant environmental and economic challenges. Recycling spent batteries and manufacturing scraps is essential for conserving critical resources such as nickel, cobalt, and manganese, while minimizing waste. However, conventional recycling methods are complex, water-intensive, and often introduce impurities that lead to quality control issues in resynthesized cathode materials. This study introduces a simplified polyol-metallurgical recycling process that uses a citric acid-ethylene glycol solution for both leaching and coprecipitation in cathode recycling. This dual-function approach eliminates complicated separation processes and avoids the introduction of impurities. The resulting precursors maintain the original chemical composition of the cathode and enable precise control over particle morphology. By applying this process to degraded NMC622 cathodes, we successfully synthesized single-crystal cathodes featuring controlled particle sizes, uniform composition, minimal structural defects, and improved electrochemical performance. The implications of this work go beyond recycling, offering a pathway to produce advanced cathode materials from waste streams, reinforcing a circular economy in battery production. By upgrading polycrystalline cathodes into single-crystal materials with high quality and guaranteed performance, the method advances multi-functional approaches to battery recycling. This innovation addresses both sustainability and performance challenges, providing the industry and society with a cleaner, more efficient solution for recovering and reusing battery materials.