Discarded sulfuric acid paper-derived hard carbon as high-performance anode material for sodium-ion batteries

Hard carbon (HC) is considered as one of the most promising electrode materials for sodium-ion batteries, while electrochemical performance of HC is highly affected by its precursors. This study explored discarded sulfuric acid paper-derived hard carbon material and the result showed that it is an excellent precursor material. The electrochemical performance, as well as revolution of the microstructure with carbonization temperatures, was systematically studied. It was found that sulfuric acid paper-derived HC pyrolyzed at the temperature of 1400 °C exhibited a high reversible capacity value of 350.1 mAh g−1 via an “ adsorption-intercalation-intercalation & pore-filling “ sodium-storage mechanism. In addition, as current density increases from 30 mA g−1 to 3 A g−1, the retention of capacity still maintain 60 % indicating a great rate performance. These findings make discarded plant fibers-based hard carbon a promising candidate for commercial application in sodium-ion batteries, achieving high reversible capacity and excellent rate performance through optimizing its microstructure via appropriate pyrolysis treatment. •Discarded sulfuric acid paper was proposed, which provides a new direction for synthesizing low-cost and sustainable electrode materials•SAPHCs achieving a reversible capacity of up to 350.1 mAh g-1, the capacity still remained at 210.2 mAh g-1 at a current density of 3 A g-1•Adsorption-intercalation-intercalation & pore-filling mechanisms were demonstrated.