Green preparation of hierarchical porous C/SiOx composites from coal gangue as anodes for Li-ion batteries

This study proposes a facile, economical, and eco-friendly strategy to prepare high stability and capacity C/SiOx composites with porous reticular cross-linked structures using solid waste coal gangue. The obtained C/SiOx composites exhibit a high reversible capacity of 1175.8 mAh/g at 0.1 A/g, with coulombic efficiency of >99.8%. Likewise, a high capacity of 430 mAh/g retains after 700 cycles at 2.0 A/g demonstrating it has an excellent reversible performance. Taking full advantage of acid soaking waste liquid, hot alkali treatment waste liquid and washing waste liquid of C/SiOx composite materials，a success was achieved in preparing metal hydroxide, low specific surface area SiO2 microspheres and NPK compound fertilizer. Moreover, the target of zero discharge and zero pollution was achieved by the ethanol and distilled water recycle during the new preparation process. [Display omitted] •Preparation of hierarchical porous C/SiOx composite using coal gangue as raw material.•Hot-alkali soaking can effectively control silicon oxide content in C/SiOx composites.•Waste liquid of hot-alkali soaking used to prepare low surface area SiO2 microspheres.•Make much of all wastewater to prepare NPK mixed fertilizer achieving zero emission.•Realize the high-value utilization of zero emission and zero pollution of coal gangue.