Effect of Na⁺ on Preparation of Biochars and Their Applications in Energy Storage

This work investigated the effect of Na₂CO₃ on the char structures of cellulose and lignin, respectively, and examined the electrochemical performance of the char by acting as an active material for coin cells. The morphology of char can be significantly steered by the concentration of Na₂CO₃. Scanning electron microscopy analysis demonstrated that the introduction of Na₂CO₃ into cellulose at an appropriate concentration led to the formation of tubular structure on its surface after pyrolysis, whereas the tubular structure was absent in the lignin char with the addition of Na₂CO₃ at any concentrations. X-ray diffraction and Raman spectroscopy characterizations revealed that all the obtained chars from both cellulose and lignin, with or without Na₂CO_3, were ascribed to non-crystalline graphite. Nevertheless, the crystal orientation of graphite from cellulose and lignin changed after the catalysis of Na₂CO₃. Further electrochemical tests showed that cellulose char had a higher sodium storage capacity than that of lignin char. The excellent electrochemical performance of carbon materials derived from cellulose might hold a prospective application in the field of energy storage.