Transforming discarded graphite into high-performance lithium-ion battery anodes: A green recycling and high-value utilization strategy for spent carbon cathode

Spent carbon cathode (SCC), a solid waste produced by the electrolytic aluminum industry mainly consists of graphite and contains various fluorides that pose significant threats to both the environment and human health. According to the primary aluminum production of 69.7587 million tons, as reported by the World Bureau of Metal Statistics, over 1 million tons of SCC were generated globally in 2023 alone. The traditional treatment method for SCC involves breaking the chemical bonds of fluoride at high temperatures or in alkaline/acidic environments to achieve purification and recovery of SCC. However, given the large volume of SCC, the use of traditional treatment methods imposes significant environmental pressures. Therefore, this article proposes a recycling strategy that combines low energy consumption with a clean process. (NH4)2SO4 is used as an additive, and through mechanical activation pretreatment, defluorination purification of SCC is achieved at a low temperature of 320 °C, resulting in graphite with a purity of 99.81 %. When used as the negative electrode in lithium-ion batteries, the purified graphite demonstrates excellent lithium-ion storage performance, including a high reversible capacity (e.g., 443.0 mAh ∙ g−1 at 0.1C), excellent rate performance (e.g., 330.81 mAh ∙ g−1 at 1C), and long-term cycling stability (e.g., 85.57 % capacity retention after 350 cycles at 1C), which fully harnesses the unique properties of recycled graphite.