Pre-carbonization and Mg powder induced synergistic optimization: Enhancing the pore structure of coffee grounds-derived hard carbon to improve sodium storage performance

Biomass-derived hard carbon, due to its abundant availability, sustainability, and natural doping with various heteroatoms, is regarded as an ideal anode material for sodium-ion batteries (SIBs). However, to address the issues of low specific capacity and initial Coulombic efficiency, it remains a key challenge to optimize the electrochemical performance of hard carbon (HC) by regulating its pore structure. To address this, we propose a novel pre-carbonization modulation strategy. In this approach, waste coffee grounds are used as the precursor, which are mixed with magnesium (Mg) powder for pre-carbonization. After the pre-treatment, the Mg powder is removed, followed by high-temperature carbonization to yield a new hard carbon material with an enhanced porous structure. Through phase characterization and electrochemical testing, we demonstrate that this method effectively promotes the formation and regulation of porosity, resulting in improved capacity for SIBs. The resulting Mg-HC-350-1300 material exhibits outstanding ionic storage performance, delivering a reversible capacity of 339.5 mAh/g at a current density of 30 mA/g. This study presents a simple, efficient, and cost-effective strategy for the development of anode materials for SIBs, with promising potential for both practical applications and environmental sustainability.