Preparation of Super Activated Carbon from Various Parts of Nelumbo nucifera and its Application as Electrode Material in Supercapacitors

In this study, five parts of Nelumbo nucifera (the lotus stem, lotus leaf, lotus seedpod, lotus seed and lotus root) were used to prepare super activated carbon with an ultra-high specific surface area. All five activated carbons were assembled into button-type supercapacitors as the electrode material. Constant current charge and discharge tests showed that under the same current density and charge/discharge voltage, the activated carbon prepared with the lotus stem has a relatively high specific capacitance of 238.52 F/g, a specific energy density of 13.7 Wh/kg and a voltage drop of less than 30 mV. After 1000 cycles, the specific capacitance remains at 89%, and the energy charge efficiency is 81%. Moreover, different MnO2 contents (mass fractions) were loaded on the activated carbon of the lotus stem to fabricate electrode materials for a supercapacitor. The test revealed that among the tested supercapacitors, the supercapacitor with 10% MnO2-loaded activated carbon from the lotus stem as an electrode material has the highest specific capacitance (323.66 F/g), which is 46.23% higher than that of a pure carbon supercapacitor, and the material resistance of this load ratio is small. The electrode prepared with a lotus stem as the carbon source has good electrochemical performance and is expected to become a new source of carbon materials for supercapacitors and low-cost energy storage devices.