Sycamore Husk-Derived Hard Carbon as Anode Material for Sodium-Ion Batteries

In this study, sycamore husk was selected as the precursor of hard carbon, and after a series process of washing,drying, grinding and impurity removal, hard carbon derived from sycamore husk-derived was successfully prepared at different carbonization temperatures. Scanning electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, Raman spectroscopy, and isothermal nitrogen absorption/desorption were used to study the effects of temperature on the surface morphology, phase structure and pore size distribution of the prepared samples, and their electrochemical performances were tested by galvanostatic charge/discharge, cyclic voltammetry, and electrochemical impedance spectroscopy. Results showed that the increase of carbonization temperature decreased the specific surface area, destroyed the internal pore structure and reduced the interlayer distance of hard carbon due to the graphitization effect. When the carbonization temperature rised to 1 000 ℃, the specific surface area of prepared hard carbon was 4.44 m²/g, which delivered the initial charge and discharge capacities of 290 mA·h/g and 400 mA·h/g, associated with the initial coulombic efficiency of 73%. The specific capacity remained as 244 mA·h/g after 100 cycles at 50 mA/g, and the diffusion coefficient of Na⁺ reached 10⁻⁸ cm²/s, accompanying excellent stability even at high rate charge/discharge process.