| 초록 |
In this study, flexible graphene stacks (FGSs) were prepared by vacuum filtration of hydrazine-treated graphene oxide (GO), followed by heating at a pressure of ~10 kPa and a temperature of 800 °C. The extensive graphitic layers composed of reduced GO (rGO) building blocks led to good mechanical and electrical properties. In addition, the monolith FGS anode had a density of 1.78 g cm-3, which is much higher than the tap density (~1 g cm-3) of conventional graphite-based electrodes. The FGSs showed an initial reversible capacity of ~163 mA h g-1 with a high Coulombic efficiency of 83% for sodium ion storage. And high rate capabilities of 4 A g-1 and stable cycling for 1,000 cycles were achieved. Furthermore, sodium ion batteries based on the FGS and a reported cathode, Na1.5VPO4.8F0.7, showed a high specific energy of ~107.7 Wh kg-1 at ~126 W kg-1, a high specific power of ~2,050 W kg-1 at 22 Wh kg-1, and good cycling performance during 50 cycles. |
