Old-loofah-derived hard carbon for long cyclicity anode in sodium ion battery

Hard carbon was prepared via the carbonization of the old loofah sponge at 800 °C for 1 h in the inert N2 atmosphere for sodium ion battery (SIB) anode. The resultant old-loofah-derived hard carbon was investigated by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), Raman, galvanostatic charge/discharge, cyclic voltammetry (CV) and alternating current (AC) impedance. The results suggested that the old-loofah-derived hard carbon powders consisted of many irregular micro-particles with the mean particle size of 12 μm. Furthermore, the old-loofah-derived hard carbon anode also delivered satisfactory electrochemical performances in SIB. For example, the initial discharge specific capacity was as high as about 695 mAh g−1 at 25 mA g−1, and the reversible discharge specific capability after 1000 cycles was still about 171 mAh g−1 even at 1000 mA g−1, indicating long cycle stability and the promising feasibility of the old-loofah-derived hard carbon anode. The disordered micro-structure and large interlayer distance may jointly contribute into the satisfactory electrochemical performances.