Purification of Waste Carbon for Battery Applications via Ascorbic Acid Leaching

Graphite is increasingly recognized as a critical material with its essential role in clean energy technologies, specifically as an anode material in lithium-ion batteries (LIBs). With the growing global demand for electric vehicles (EVs) and supply risks, finding alternative sources has become necessary. Waste carbon (WC) materials, which have significant graphite content, offer a promising secondary source for battery applications. Despite developments in recycling technologies, most efforts remain focused on cathode materials from spent LIBs and rely on corrosive leaching agents that are challenging to manage and impact the environment through emissions. Thus, it is essential to advance research focused on waste carbon recycling, and this study seeks to develop a green leaching technology using ascorbic acid to purify waste carbon, particularly graphitic waste from the Acheson furnace, with about 99.85% purity. The effectiveness of ascorbic acid has been investigated for removing impurities like Fe, Al, Ca, and S. A 2-level factorial design was employed using Stat-Ease Design Expert (DOE) software to identify the significant factors and interactions between selected variables such as acid concentration, temperature, and time. The effective removal of Fe, Al, Ca, and S using ascorbic acid leaching demonstrated the potential to enhance the graphite purity to >99.95%, meeting the minimum purity required for battery-grade applications.