A Comparative Investigation on Lithium Storage Performance of Carbon Microsphere Originated from Agriculture Bio-waste Materials: Sunflower Stalk and Walnut Shell

With the aggravation of environmental pollution and the reduction of fossil fuels, the need of developing green and environmentally sustainable energy materials is becoming urgent. Novel porous carbon microsphere materials derived from waste biomass sunflower steam and walnut shell were prepared based on acidolysis-hydrothermal method, and the morphology, structure and electrochemical performance of the products were characterized by scanning electron microscope, transmission electron microscopy, Raman, X-ray diffraction measurements, nitrogen adsorption, X-ray photoelectron spectroscopy, galvanostatic charge-discharge, cyclic voltammograms and electrochemical impedance spectroscopy. Different electrochemical performance for Li-ion storage was demonstrated owing to the variation of physical property and electrode interface behavior. As an anode material for lithium-ion batteries, the carbon material derived from walnut shell exhibits higher initial coulombic efficiency, cycling stability and rate performance. It can retain charge capacity of 235.3 mAh g(-1) after 50 cycles, which is obviously higher than that of carbon microsphere from sunflower steam, 145.9 mAh g(-1), and the capacity retention of walnut shell material is 2.5 times that of sunflower steam. It is believed that the superior electrochemical performance may be attributed to the higher graphitization degree and larger pore path of walnut shell-derived carbon materials with average particle size of 3-5 mu m, and higher conductivity of SEI film formed on the surface of electrode, which can enhance the conductivity of bulk material and accelerate the migration of lithium ion through bulk material and electrode/electrolyte interface.