It is very important to recycle the waste biomass resources for the environment protection and the circular economy. For this purpose, the waste old loofah was carbonized at 800°C for 1 h in the inert nitrogen gas (N2) atmosphere for lithium ion battery anode. The resultant waste-loofah-derived carbon was investigated by scanning electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, nitrogen adsorption and desorption, galvanostatic charge/discharge, cyclic voltammetry and alternating current impedance. The results suggested that the waste-loofah-derived carbon powders consisted of many concomitant microparticles and nanoparticles with a specific surface area of about 492 m2/g. Furthermore, the waste-loofah-derived carbon anode also delivered high electrochemical lithium (Li) storage activity. For example, the initial specific discharge capacity was about 697 mAh/g, and the reversible discharge capacity was about 187 mAh/g at 1000 mA/g for 500 cycles and still about 98 mAh/g even at 3000 mA/g for 500 cycles, exhibiting good cycling stability. High surface area and structural defects may jointly contribute to high electrochemical performances.

Sodium p-toluenesulfonate (TsONa)-doped polypyrrole (PPy) was synthesized as the cathode active material of sodium ion battery by way of facile one-step electrodeposition on iron (Fe) foil. The micro-morphology and micro-structure of assynthesized TsONa/PPy/iron cathode were characterized in terms of scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction; furthermore, the electrochemical Na-storage activity of TsONa/PPy/iron cathode was investigated by methods of, galvanostatic charge/discharge, cyclic voltammetry and alternating current impedance. As expected, the cauliflower-like TsONa-doped PPy particles tightly combined with the surface of the iron foil without any additional polymer binders; and also, the resultant TsONa/PPy/iron cathode delivered satisfactory electrochemical performances, mainly attributed to high Na-storage activity of PPy matrix and high electronic conductivity induced by doping of TsONa. For example, the reversible discharge capacity of TsONa/PPy/iron cathode remained about 98 mAh/g after at least 50 cycles and the corresponding coulombic efficiency was 92%, indicating high cyclic stability and reversibility of TsONa/PPy/iron cathode for sodium ion battery.