Acid Leaching-Assisted Purification of Natural Graphite for Enhanced Electrochemical Performance in Lithium-Ion Batteries

Natural graphite is widely recognized as an anode material for lithium-ion batteries because of its high theoretical capacity, low lithiation potential, natural abundance, and affordability. However, to use natural graphite effectively, impurities must be removed to meet battery-grade standards and ensure stable electrochemical performance. In this study, natural graphite was carefully purified by using chemical and thermal processes. A new chemical method was developed using 30% H 2 SO 4 and 30% NH 4 F, heated to 90°C, to meet battery-grade standards, achieving a final purity of nearly 99.9%. SEM-EDS characterization was performed to confirm impurity removal and morphology remained unchanged after purification, while XRD analysis was used to verify the graphite structure.Importantly, there were no significant changes in particle shape or size after purification. Higher purity not only improves the reversible capacity but also enhances cycling stability. This is mainly because impurity reduction helps prevent electrolyte decomposition and promotes a more stable electrode/electrolyte interface. The performance of the purified graphite aligns well with expectations for high-quality battery anode materials. Overall, this work emphasizes that purification is a crucial step in turning natural graphite into a reliable, high-performance material for lithium-ion batteries.