Treasure Na-ion anode from trash coke by adept electrolyte selection

Converting 'trash' waste residua to active functional materials 'treasure' with high added value is being regarded as a promising way to achieve the sustainable energy demands. Carbonaceous materials cannot insert sodium except when graphite co-intercalates solvents such as diglyme. Here; we show that petroleum coke and shale coke annealed at different temperatures can also insert sodium by reversible intercalation phenomena in a diglyme-based electrolyte. The structural and morphological studies will reveal significant differences justifying their distinct electrochemical behavior. Galvanostatic tests exhibit a flat plateau at about 0.7 V ascribable to the reversible reaction. At the end of the discharge, a Stage-I ternary intercalation compound is detected. Two diglyme molecules are co-intercalated per alkali ion, as evidenced by 1-D Patterson diagrams, FTIR and TGA analyses. The full sodium-ion cell made with P-2500/NaPF6(diglyme)/Na3V2(PO4)(3) delivered an initial reversible capacity of 75 mA h g(-1) at C rate and an average potential of 2.7 V. Thus, the full cell provides an energy density of 202 W h kg(-1). This sodium-ion system can be considered a promising power source that encourages the potential use of low-cost energy storage systems. (C) 2017 Elsevier B.V. All rights reserved.